Riyaz Kharrat

Verified email at put.ac.ir

Petroleum University of Technology



                     

http://researchid.co/riyazkharrat
282

Scopus Publications

Scopus Publications

  • Static and dynamic behavior of foam stabilized by modified nanoparticles: Theoretical and experimental aspects
    Muhammad Suleymani, Siavash Ashoori, Cyrus Ghotbi, Jamshid Moghadasi, and Riyaz Kharrat

    Chemical Engineering Research and Design, ISSN: 02638762, Volume: 158, Pages: 114-128, Published: June 2020 Elsevier BV

  • Theoretical and experimental study of foam stability mechanism by nanoparticles: Interfacial, bulk, and porous media behavior
    Muhammad Suleymani, Cyrus Ghotbi, Siavash Ashoori, Jamshid Moghadasi, and Riyaz Kharrat

    Journal of Molecular Liquids, ISSN: 01677322, Volume: 304, Published: 15 April 2020 Elsevier BV

  • Experimental investigation of smart carbonated water injection method in carbonates
    Payam Soleimani, Seyed Reza Shadizadeh, and Riyaz Kharrat

    Greenhouse Gases: Science and Technology, eISSN: 21523878, Pages: 208-229, Published: 1 February 2020 Wiley

  • Stability, flocculation, and rheological behavior of silica suspension-augmented polyacrylamide and the possibility to improve polymer flooding functionality
    Reza Elhaei, Riyaz Kharrat, and Mohammad Madani

    Journal of Molecular Liquids, ISSN: 01677322, Published: 2020 Elsevier BV

  • Experimental assessment of hybrid smart carbonated water flooding for carbonate reservoirs
    Payam Soleimani, Seyed Reza Shadizadeh, and Riyaz Kharrat

    Petroleum, ISSN: 24056561, eISSN: 24055816, Published: 2020 Elsevier BV

  • A novel test method for evaluate asphaltene inhibitor efficiency on damage permeability
    Mohammad Ali Karambeigi, Narges Fallah, Manouchehr Nikazar, and Riyaz Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 2146-2149, Published: 18 October 2019 Informa UK Limited
    Abstract Asphaltene deposition has a significant detrimental effect on oilfield production. The key to effective treatment of asphaltene deposition is recognition of the problem. Asphaltene and effective treatment can be identified and quantified using laboratory methods. The most commonly way to asphaltene precipitation reduction is applying an asphaltene inhibitor. Most researchers investigate the effect of asphaltene inhibitors on fluid and precipitation reduction in static tests. This study is a coherent approach to measure effect of asphaltene precipitation on reservoir permeability and survey effect of asphaltene inhibitors on damage permeability.

  • A novel test method for evaluate asphaltene inhibitor efficiency on reservoir rock
    Mohammad Ali Karambeigi, Narges Fallah, Manouchehr Nikazar, and Riyaz Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1238-1242, Published: 3 June 2019 Informa UK Limited
    Abstract Asphaltene deposits can reduce the productivity of the reservoir as well as foul piping and surface equipment. Current chemical and mechanical methods for treating deposition are only partially effective partly because the deposition process is poorly understood. The most commonly way to asphaltene precipitation reduction is applying an asphaltene inhibitor. In order to investigate the extent of formation damage by asphaltenes in crude oil this work has used electro kinetic technique to study the adsorption of asphaltenes in rock pores. Most researchers investigate the kinetics of adsorption by monitoring changes in the concentration of asphaltene or polymer in a dispersion of adsorbent particles or capillaries. This study is a coherent approach to measure amount of asphaltene adsorption on rock surface and survey effect of asphaltene inhibitors on precipitation reduction in porous media.

  • Screening of inhibitors for remediation of asphaltene deposits: Experimental and modeling study
    Mehdi Madhi, Riyaz Kharrat, and Touba Hamoule

    Petroleum, ISSN: 24056561, eISSN: 24055816, Pages: 168-177, Published: June 2018 Elsevier BV

  • Experimental evaluation of carbonated waterflooding: A practical process for enhanced oil recovery and geological CO2 storage
    Puyan Bakhshi, Riyaz Kharrat, Abdolnabi Hashemi, and Mehdi Zallaghi

    Greenhouse Gases: Science and Technology, eISSN: 21523878, Pages: 238-256, Published: April 2018 Wiley
    The rapid escalation of anthropogenic CO2 emissions at the same time as the growth in energy demand has brought the importance of CO2 enhanced oil recovery (EOR) into the spotlight. Nevertheless, fundamental problems with conventional CO2 injection have paved the way for practicing other strategies, such as carbonated waterflooding (CWF), i.e., flooding of CO2 dissolved in flood water through the reservoir. In this work, performance of CWF as a joint method of EOR and CO2 storage in an Iranian oil field is examined through sets of coreflooding experiments, conducted at a specified pressure and temperature condition on two different reservoir oil (light and heavy) and rock (carbonate and sandstone) samples from the investigated oil field. In summary, CWF improved the oil recovery as compared to waterflooding (WF). Average recovery factors (RFs) for CWG ranged from 6.4% to 13.6% when implemented as a secondary recovery technique and 4.2% to 4.8% when used as a tertiary recovery technique. This improvement was also higher in the carbonate rock than in the sandstone one, slightly higher with light oil than with heavy oil, and lower when a more saline brine was used for carbonated water preparation. CWF also showed to be more effective when implemented in a mixed-wet system than in a water-wet one. Moreover, considerable amounts (about 42‒60%) of the CO2 injected through the flooding brine were ultimately stored in the porous media. Finally, a co-optimizing function was used as a standard for coupling CO2 EOR and storage. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

  • Improving the microscopic sweep efficiency of water flooding using silica nanoparticles
    Mehdi Zallaghi, Riyaz Kharrat, and Abdolnabi Hashemi

    Journal of Petroleum Exploration and Production Technology, ISSN: 21900558, eISSN: 21900566, Pages: 259-269, Published: 1 March 2018 Springer Science and Business Media LLC
    Fluid/fluid and fluid/rock interfaces have large influence on the microscopic sweep efficiency of an enhanced oil recovery process. Therefore, modification of these interfaces using nanoparticles to suitable conditions might lead to better recovery factors. Particularly, wettability alteration and interfacial tension reduction are the two key mechanisms which should be considered. This study was designed to address the capability of nanoparticles to be used as a chemical agent for enhanced oil recovery by several core flooding experiments. The injected chemical solution was prepared using synthetic brine containing %3 NaCl, silica nanoparticles, and SDS surfactant. Contact angle in rock/oil/solution system and interfacial tension between oil/solution were measured. In addition, SEM pictures and XRD analysis were taken to conduct a more thorough investigation of effect of nanoparticles on sandstone core plugs. Nanoparticles and surfactant mixture were flooded with various concentrations under different scenarios. The results show the incremental oil recovery of nanoparticles floods in sandstone core samples which ranged from 4.85 to 11.7%. Conversely, the enhanced oil recovery of high concentration of nanoparticle floods in cores was small. It is deduced that the mechanisms responsible for incremental oil recovery are mainly interfacial tension reduction and wettability alteration toward water-wet condition. However, the flooding results as well as experimental study of possible retention revealed that nanoparticles can be considered as an effective chemical agent in enhanced oil recovery.



  • Estimating the properties of naturally fractured reservoirs using rate transient decline curve analysis
    Amin Daryasafar, Mohammad Joukar, Mohammad Fathinasab, Giovanni Da Prat, and Riyaz Kharrat

    Journal of Earth Science, ISSN: 1674487X, Pages: 848-856, Published: 1 October 2017 Springer Science and Business Media LLC
    Transient rate decline curve analysis for constant pressure production is presented in this paper for a naturally fractured reservoir. This approach is based on exponential and constant bottom-hole pressure solution. Based on this method, when ln (flow rate) is plotted versus time, two straight lines are obtained which can be used for estimating different parameters of a naturally fractured reservoir. Parameters such as storage capacity ratio (ω), reservoir drainage area (A), reservoir shape factor (CA), fracture permeability (kf), interporosity flow parameter (λ) and the other parameters can be determined by this approach. The equations are based on a model originally presented by Warren and Root and extended by Da Prat et al. and Mavor and Cinco-Ley. The proposed method has been developed to be used for naturally fractured reservoirs with different geometries. This method does not involve the use of any chart and by using the pseudo steady state flow regime, the influence of wellbore storage on the value of the parameters obtained from this technique is negligible. In this technique, all the parameters can be obtained directly while in conventional approaches like type curve matching method, parameters such as ω and λ should be obtained by other methods like build-up test analysis and this is one of the most important advantages of this method that could save time during reservoir analyses. Different simulated and field examples were used for testing the proposed technique. Comparison between the obtained results by this approach and the results of type curve matching method shows a high performance of decline curves in well testing.

  • Comparison and evaluation of several models in prediction of asphaltene deposition profile along an oil well: a case study
    Peyman Kor, Riyaz Kharrat, and Abdoljalal Ayoubi

    Journal of Petroleum Exploration and Production Technology, ISSN: 21900558, eISSN: 21900566, Pages: 497-510, Published: 1 June 2017 Springer Science and Business Media LLC
    Deposition of asphaltenes on the inner surface of oil wells and pipelines causes flow blockage or significant production loss in these conduits. Generally, asphaltenes are stable in reservoir condition; however, change in pressure, temperature, and composition can trigger phase separation and then deposition of asphaltene along the flow stream. Therefore, it is required to identify the possibility of asphaltene precipitation and accurately quantify deposition tendency of these heavy organic molecules. This work is aimed at detailed assessment of the predictive capability of five deposition models available in the literature for calculating the magnitude and profile of asphaltene deposition in wellbores. To end this, firstly we discuss and describe these five models known as Friedlander and Johnstone (Ind Eng Chem 49:1151–1156, 1957), Beal (Nucl Sci Eng 40:1–11, 1970), Escobedo and Mansoori (SPE annual technical conference and exhibition, 1995), Cleaver and Yates (Chem Eng Sci 30:983–992, 1975), and Jamialahmadi et al. (Int J Heat Mass Transf 52:4624–4634, 2009). Afterward, thermodynamic modeling of live oil and a wellbore P–T relationship of the flowing fluid were used in a graphical method in order to identify asphaltene precipitation zone along axial wellbore length. Then, the five models were applied to the wellbore to forecast the deposition tendency of precipitated asphaltene particles and to obtain a profile of deposited asphaltenes. Most importantly, a measured deposit profile of the investigated wellbore enabled us to select the most accurate one for estimating the asphaltene deposition rate. The validation method presented in this work reveals that Cleaver and Yates (1975), Jamialahmadi et al. (2009), and Escobedo and Mansoori (1995) models have a satisfactory performance in predicting asphaltene deposition profile along the wellbore when compared to caliper measurement of the well.

  • Forecasting gas density using artificial intelligence
    Abouzar Choubineh, Elias Khalafi, Riyaz Kharrat, Alireza Bahreini, and Amir Hossein Hosseini

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 903-909, Published: 3 May 2017 Informa UK Limited
    ABSTRACT Proper calculations of gas engineering require precise determination of gas properties and its associated variations with pressure and temperature. These properties can be determined by conducting experimental tests on gathered fluid samples from the bottom of the wellbore or at the surface as well as using equations of state and empirical correlations. This work is concentrated to develop a robust and quick model based on artificial network trained with teaching learning based optimization (ANN-TLBO) using 693 data sets at a wide range of pressure and temperature for gas density prediction. Comparing gas density from the predictive method and experimental results describe that the proposed ANN-TLBO model is of reliable accuracy for determining gas density. Sensitivity analysis also showed the extreme effect of temperature and pressure on gas density.

  • Prediction of asphaltene precipitation during gas injection
    Hossein Lashkari, Riyaz Kharrat, and Ali Reza Khaz'ali

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 271-278, Published: 1 February 2017 Informa UK Limited
    ABSTRACT Maintaining the flow of multiphase fluid from the reservoir to the surface has been an important issue with wide economic importance for the petroleum industry. Asphaltene precipitation due to change in temperature, pressure, and composition of oil can adversely affect the oil flow to the surface by reducing the available diameter of the tubing. In this study, the precipitation of asphaltene from an Iranian crude oil was investigated. To do our study, through information about asphaltene instability in the live oil during both natural depletion and gas injection conditions about oil sample from Iranian oil field was gathered. Then, the solid model and scaling model were utilized to predict the weight percent of precipitated asphaltene at a wide range of the pressure and temperature. Results of the work revealed that both models predict the increase in weight percent of precipitated asphaltene when lean gas injected to the live oil at the maximum point of asphaltene instability. In addition, the study showed that both models are capable of predicting the experimental data of asphaltene precipitation; while scaling modeling is more reliable when the gas is injected to the oil.

  • Asphaltene precipitation modeling by using of PC-SAFT equation of state
    B. Soltani, S. Esteghamat, and R. Kharrat

    79th EAGE Conference and Exhibition 2017, Published: 2017 EAGE Publications BV

  • Optimizing the location of the gas injection well during gas assisted gravity drainage in a fractured carbonate reservoir using artificial intelligence
    Naser Akhlaghi, Riyaz Kharrat, and Fatemeh Rezaei

    Theoretical Foundations of Chemical Engineering, ISSN: 00405795, Pages: 65-69, Published: 1 January 2017 Pleiades Publishing Ltd
    Gas assisted gravity drainage (GAGD) is a novel subdivision of gas injection method. In this method the injection wells are located in the upper bed of the oil zone, and the production wells are drilled at the bottom bed of the oil zone. Reservoir simulation is among the decision tools for investigating production rate and selecting the best scenarios for developing the oil and gas fields. Selecting the location of the injection wells for reaching the optimized pressure and production rate is one of the most significant challenges during the injection process. Recent experiences have shown that artificial intelligence (AI) is a reliable solution for taking the mentioned decision appropriately and in a least possible time. This study is attributed to the investigation of applying the artificial neural network (ANN) as an artificial intelligence method and a potent predictor for choosing the most proper location for injection in a GAGD process in a fractured carbonate reservoir. The results of this investigation clearly show the efficiency of the ANN as a powerful tool for optimizing the location of the injection wells in a GAGD process. The comparison between the results of ANN and black oil simulator indicated that the predictions obtained from the ANN is highly reliable. In fact the production flow rate and pressure can be obtained in every possible location of the injection well.

  • Characterization of asphaltene deposition process in flow loop apparatus; An experimental investigation and modeling approach
    Ali Khorram Ghahfarokhi, Peyman Kor, Riyaz Kharrat, and Bahram Soltani Soulgani

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 151, Pages: 330-340, Published: 2017 Elsevier BV

  • Estimation of carbonates permeability using pore network parameters extracted from thin section images and comparison with experimental data
    Arash Rabbani, Ali Assadi, Riyaz Kharrat, Nader Dashti, and Shahab Ayatollahi

    Journal of Natural Gas Science and Engineering, ISSN: 18755100, Pages: 85-98, Published: 2017 Elsevier BV

  • Modeling of asphaltene particle deposition from turbulent oil flow in tubing: Model validation and a parametric study
    Peyman Kor and Riyaz Kharrat

    Petroleum, ISSN: 24056561, eISSN: 24055816, Pages: 393-398, Published: December 2016 Elsevier BV

  • Visualization and analysis of viscous fingering in alcohol-assisted surfactant waterflooding of heavy oil in a two-dimensional sandstone micromodel
    Benyamin Yadali Jamaloei, Rana Babolmorad, and Riyaz Kharrat
    ISSN: 00162361, Volume: 184, Pages: 169-179, Published: 15 November 2016 Elsevier BV

  • Prediction of the asphaltene deposition profile along a wellbore during natural production from a reservoir
    Peyman Kor and Riyaz Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2837-2844, Published: 1 October 2016 Informa UK Limited
    ABSTRACT The potential problem of asphaltene deposition during oil production has motivated both academics and industries to predict the asphaltene deposit profile in wellbores and pipelines. In this work, asphaltene deposition profile along an oil field well with the severe problem of asphaltene deposition was predicted. To do this, a comprehensive simulator for modeling of flow parameters such as pressure, temperature, and composition for a multiphase flow of oil, gas, and asphaltene from the reservoir to the surface was developed and coupled with the deposition model. By applying the simulator to an oil field well, it has been found that 60–70% of the total asphaltene thickness formed after 1 month of production, indicating that the problem of asphaltene deposition is bound to the initial stage of wellbore life. Moreover, the simulator was able to predict the accumulated asphaltene thickness and the time of wellbore plugging properly. This prediction is highly crucial if it is aimed to control the well performance and to optimize the productivity.

  • Correlations of viscous fingering in heavy oil waterflooding
    Benyamin Yadali Jamaloei, Rana Babolmorad, and Riyaz Kharrat
    ISSN: 00162361, Volume: 179, Pages: 97-102, Published: 1 September 2016 Elsevier BV

  • Case study: Comparison of enhanced heavy-oil recovery by CGI, WAG, and GAGD
    Zohreh Tavousi, Riyaz Kharrat, Abdolnabi Hashemi, and Eshragh Ghoodjani

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2181-2189, Published: 2 August 2016 Informa UK Limited
    ABSTRACT Continuous gas injection (CGI) in the conventional horizontal flooding patterns leads to severe gravity segregation and poor reservoir contact (sweep) volumes. To improve the sweep efficiency, the Water-Alternating-Gas (WAG) process has been widely practiced in the industry. However, the WAG process has not measured up to expectations, as evidenced by the low recoveries observed in several field cases. The Gas-Assisted Gravity Drainage (GAGD) process is designed and practiced based on gravity drainage idea and uses the advantage of density difference between injected gas and reservoir oil to overcome the drawbacks of the WAG process. In this study, a comparison of enhanced heavy-oil recovery by three methods (CGI, WAG, and GAGD) is conducted by a commercial numerical simulator in a sector model of an Iranian offshore field. For this purpose, different production scenarios are designed. Moreover, the effect of several parameters such as injection fluid (CO2, hydrocarbon gas), in situ oil viscosity (heavy or extremely heavy oil), rate and volume of injection, and also three different WAG ratios are studied. The results show that the GAGD method is not suitable for this field as the thickness of pay zone is low for vertical sweep efficiency and causes early breakthrough of injected gas. Also, CGI leads to lower recoveries compared to the WAG process, due to its unfavorable mobility ratio. Injection of CO2 instead of hydrocarbon gas results in higher sweep efficiency because of its viscosity reduction and swelling effects. In case of extremely heavy-oil recovery, with decreasing well spacing, the oil recovery factor increases as the drainage radius of wells reduces substantially due to high-viscosity oil.

  • Study the effect of fracture inclination, spacing and intensity on polymer flooding efficiency
    Behbood Abedi and Riyaz Kharrat

    Journal of Natural Gas Science and Engineering, ISSN: 18755100, Pages: 645-649, Published: 1 August 2016 Elsevier BV

  • Estimation of 3-D pore network coordination number of rocks from watershed segmentation of a single 2-D image
    Arash Rabbani, Shahab Ayatollahi, Riyaz Kharrat, and Nader Dashti

    Advances in Water Resources, ISSN: 03091708, Pages: 264-277, Published: 1 August 2016 Elsevier BV

  • Numerical and ANFIS modeling of the effect of fracture parameters on the performance of VAPEX process
    Heydar Pendar, Mehdi Mohammad Salehi, Riyaz Kharrat, and Saeed Zarezadeh

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 143, Pages: 128-140, Published: July 01, 2016 Elsevier BV

  • Experimental and theoretical study of asphaltene deposition and permeability impairment in low-permeability carbonate cores
    Afsaneh Raz, Kamyar Movagharnejad, Riyaz Kharrat, and G. Reza P. Oskui

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1604-1611, Published: 2 June 2016 Informa UK Limited
    ABSTRACT Asphaltene deposition is one of the problems that oil industries face during oil production, processing, transport, and refining. Deposition of asphaltene flocculation on reservoir rock can plug pore spaces and cause permeability impairment. Carbonate rock, which has low permeability, tend to adsorb asphaltene causing more loss of permeability. In this study, three miscible CO2 injection core tests were conducted at reservoir conditions and the effects of asphaltene content on the amount of formation damage in carbonate cores with low permeability were investigated. High asphaltene content oil has been used in the experiments. Results show that permeability reduction was more than porosity losses. An empirical model for permeability impairment was derived based on experimental data by considering the activation of the two mechanisms simultaneously. The results may be useful for understanding permeability impairment mechanisms during gas injection in low-permeability carbonate cores.

  • Prediction of asphaltene deposition parameters in porous media using experimental data during miscible gas injection
    Afsaneh Raz, Kamyar Movagharnejad, Riyaz Kharrat, and G. Reza P. Oskui

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1620-1627, Published: 2 June 2016 Informa UK Limited
    ABSTRACT The study of asphaltene deposition under actual field conditions is impossible. Therefore, many models have been derived based on experimental data. All models have some matching parameters, which are estimated along with numerical solving or simulation to match experimental and simulation data, so it is possible that these were estimated as required (tuning factor). In this study, two miscible CO2 injection dynamic tests in porous media were performed. In these tests, CO2 and live oil were injected into the core simultaneously. The CO2 concentration was more than the onset concentration for asphaltene precipitation. The main objective of this work was to determine the deposition coefficients from the experimental data, so these were predicted by using basic equations using the material balance. Also, by mathematical methods, the relation between these parameters was determined. Results from this work imply that the deposition parameters can be estimated from the experimental data and these parameters are not constant during modeling and simulation.

  • Investigation of the asphaltene deposition along the flow of the oil in tubing: Experimental study and a parametric analysis
    Ali Khorram Ghahfarokhi, Riyaz Kharrat, and Bahram Soltani Soulgani

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 884-890, Published: 18 May 2016 Informa UK Limited
    ABSTRACT In this work, a novel experimental setup was designed and utilized to carry out the n-alkane induced asphaltenes for understanding the kinetics of deposition and also effects of oil velocity, oil-precipitant volumetric dilution ratio, and temperature on the rate of asphaltene deposition. As the deposited layer of asphaltenes makes it difficult for the flow of oil along the tube, measurement of the pressure drop across the tube section of setup enabled the measurement of the amount and extent of deposition process at desired condition. The experimental results revealed that increasing the velocity of fluid across the pipe dominance the shear force on asphaltene deposit and cause remobilization of part of the deposit into the flowing fluid in contrary to oil-precipitant ratio, where deposition rate is enhanced with increasing DR ratio. The results of this work elucidate some less-addressed shadows of dynamics of flow blockage in pipelines and could create a better framework for conducting forthcoming experiments

  • A novel approach for asphaltene inhibitor modeling
    Mohammad Ali Karambeigi, Manouchehr Nikazar, and Riyaz Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 274-279, Published: 1 February 2016 Informa UK Limited
    ABSTRACT Asphaltenes are typically defined by solubility as benzene soluble and pentane or heptane insoluble. The most common way to asphaltene precipitation reduction is to apply an asphaltene inhibitor. As preliminary trial for inhibitor modeling, some procedures were applied. The most common way is to use known components of inhibitors. Because of some defects in this way, this option was also not adopted. However, simulation software has not included inhibitor option for asphaltene modeling yet. Therefore, we tried to reproduce the effect of inhibitor in this study based on the established models, using commercial inhibitors through the experimental procedure. This study is a new driver for asphaltene inhibitor modeling analysis. The workflow of this method was established by estimating physical properties of the target inhibitor treated as a pseudocomponent, defining the target inhibitor in the base model with the estimated physical properties, drawing ADE on phase diagram, comparing the simulated and experimental ADE diagram, and matching correlations with changing acentric factor.

  • Experimental evaluation of asphaltene inhibitors selection for standard and reservoir conditions
    Mohammad Ali Karambeigi, Manouchehr Nikazar, and Riyaz Kharrat

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 137, Pages: 74-86, Published: January 01, 2016 Elsevier BV

  • On the Analysis of Well Test Data Influenced by Capillary Pressure
    E. Nikjoo, R. Kharrat, A. Jahanbakhsh, and A. Emamzadeh

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Issue: 21-22, Pages: 1808-1814, Published: 17 November 2015 Informa UK Limited
    The focus of this study is on the analysis of capillary pressure effects on well test data. Ignoring the capillary pressure is one of the assumptions that have been applied in all multiphase well test analysis approaches. In this work we investigate the influences of capillary pressure on the analysis of pressure transient data in a solution gas drive reservoir and in a reservoir containing oil and water. Reservoir simulations were performed to generate pressure and saturation data for each case and the pressure responses and the fluids saturation distribution for drawdown and build-up tests for two cases with and without capillary pressure are compared. According to the results of this study, it has been concluded that the influences of capillary pressure on fluids saturation behavior in build-up test due to importance of capillary force than viscose force in this period is more noticeable. Though the effects of capillary pressure lead to differences in the fluids saturation behavior but the authors have not observed dissimilarity in the pressure responses affected by capillary pressure for draw down and build-up test in the both reservoirs under study.

  • Prediction of the gas injection effect on the asphaltene phase envelope
    Peyman Bahrami, Riyaz Kharrat, Sedigheh Mahdavi, and Hamed Firoozinia

    Oil and Gas Science and Technology, ISSN: 12944475, eISSN: 19538189, Pages: 1075-1086, Published: 1 November 2015 EDP Sciences

  • Prediction of the Shear Wave Velocity from Compressional Wave Velocity for Gachsaran Formation
    Saeed Parvizi, Riyaz Kharrat, Mohammad R. Asef, Bijan Jahangiry, and Abdolnabi Hashemi

    Acta Geophysica, ISSN: 18956572, eISSN: 18957455, Pages: 1231-1243, Published: October 2015 Springer Science and Business Media LLC
    Shear and compressional wave velocities, coupled with other petrophysical data, are very important for hydrocarbon reservoir characterization. In situ shear wave velocity (Vs) is measured by some sonic logging tools. Shear velocity coupled with compressional velocity is vitally important in determining geomechanical parameters, identifying the lithology, mud weight design, hydraulic fracturing, geophysical studies such as VSP, etc. In this paper, a correlation between compressional and shear wave velocity is obtained for Gachsaran formation in Maroon oil field. Real data were used to examine the accuracy of the prediction equation. Moreover, the genetic algorithm was used to obtain the optimal value for constants of the suggested equation. Furthermore, artificial neural network was used to inspect the reliability of this method. These investigations verify the notion that the suggested equation could be considered as an efficient, fast, and cost-effective method for predicting Vs from Vp.

  • Static Stability of Liquid Bridges between Matrix Blocks of a Gas Invaded Zone of Naturally Fractured Reservoirs
    R. Miri, S. R. Shadizadeh, and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Issue: 17-18, Pages: 1541-1551, Published: 17 September 2015 Informa UK Limited
    A large portion of oil and gas reservoirs in the world are located in naturally fractured reservoirs. Despite such importunity, the production mechanisms of these reservoirs are not completely well defined. Gas–oil gravity drainage that takes place in the gas-invaded zone of this type of reservoirs is one instance of such a weakness. The density difference between gas-filled fractures in contact with oil-saturated matrix blocks brings the oil out of the matrix blocks into the fracture. The drained oil can reach the production well through two different paths: continues fracture network and block-to-block path. These two different paths require different approaches to modeling of gravity drainage. Single-block approaches are used when drained oil only travels through the fracture network, which totally formulated before. But when oil prefers to travel through the matrix blocks, continuum approaches such as Darcy's law may not work in their basic forms any more. Liquid bridges and film that form in the horizontal fracture between matrix blocks usually transfer the wetting phase across the fracture. Stability condition and duration of stability can help better understanding of gravity drainage in stacks of blocks. In this article, the stability of liquid bridges between the matrix blocks studied and a minimum length of stability is predicated. The results show that this stable length of liquid bridges formed between adjacent matrix blocks is 2r0π, which is a function of the pore throat. This critical length can be used in modeling of capillary continuity and wetting phase transfer across matrix blocks.

  • Fully implicit compositional simulator for modeling of asphaltene deposition during natural depletion
    Gholamreza Fallahnejad and Riyaz Kharrat

    Fluid Phase Equilibria, ISSN: 03783812, Volume: 398, Pages: 15-25, Published: July 05, 2015 Elsevier BV

  • Experimental investigation of matricaria chamomilla extract effect on oil-water interfacial tension: Usable for chemical enhanced oil recovery
    S. S. Shadizadeh and Riyaz Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 901-907, Published: 18 April 2015 Informa UK Limited
    Recently, natural surfactants had been studied for chemical enhanced oil recovery as opposite to synthetic surfactants due to environmental problems associated with synthetic surfactants. In this study a new plant based natural surfactant, Matricaria chamomilla, is introduced. For this purpose, the interfacial tension values between natural surfactant solution and oil are measured by using the pendant drop method. The results show that Matricaria chamomilla decreased the oil-water interfacial tension values from 30.63 to 12.57 mN/m. Results confirm surface chemical activity of Matricaria chamomilla in comparison with other natural surfactants.

  • Optimization of solvent composition and injection rate in vapour extraction process
    Ali Esfandyari Bayat, Radzuan Junin, Riyaz Kharrat, Shahaboddin Shamshirband, Shatirah Akib, and Zolkepli Buang

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 128, Pages: 33-43, Published: April 01, 2015 Elsevier BV

  • Enhancement of surfactant flooding performance by the use of silica nanoparticles
    Mohammad Zargartalebi, Riyaz Kharrat, and Nasim Barati
    ISSN: 00162361, Volume: 143, Pages: 21-27, Published: 15 March 2015 Elsevier BV
    Abstract One of the most significant current discussions in petroleum industry is the use of nanotechnology to improve oil recovery. The aim of this study is the implication of silica nanoparticles in combination with anionic surfactant to see if the surfactant properties are influenced in the presence of nanoparticles and to investigate the capability of these particles to enhance oil recovery. Extensive series of interfacial tension and adsorption measurement experiments were performed. It was observed that surfactant adsorption amount was mostly reduced when mixed with nanoparticles. Interfacial tension measurements revealed strange behavior in low and high surfactant concentrations. The optimum conditions for various scenarios of surfactant flooding were selected upon various experimental results. The flooding experiments showed that nanoparticles could efficiently improve surfactant performance by enhancing the governing mechanisms and the oil recovery was consequently increased by a considerable amount.

  • Investigation of Inhibitors Performance on Different Asphaltenic Crude Oils
    M. A. Karambeigi, R. Kharrat, and S. Mahdavi

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1715-1722, Published: 18 August 2015 Informa UK Limited
    Asphaltene deposition is an ever-increasing problem at Iranian oil reservoirs and in many fields worldwide. Several procedures are used to remove or prevent asphaltene precipitation, but the uses of asphaltene inhibitors provide the most practical and economical solution for treatment of deposits. It is necessary to know the performance of an inhibitor before its application in the field. In this work performance of five inhibitors, namely, benzoic acid, nonylphenol, phenanthrene, phthalic acid, and salicylic acid on three types of Iranian oil with asphaltene content ranging from 0.321, 14.89, and 24.73% have been studied. The optimum concentration of each inhibitor was obtained. The results revealed that salicylic acid has the best efficiency on precipitation reduction for all cases of crudes.

  • Proper implementation of gas-oil gravity drainage transfer functions in dual porosity simulators
    R. Miri, S. R. Shadizadeh, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1133-1144, Published: 19 May 2015 Informa UK Limited
    Free fall and forced gravity drainage are established production mechanisms, which contribute to significant oil production in naturally fractured reservoirs, commonly 30–60% original oil in place. Accurate and proper implementation of gravity drainage performance, as an exchange term, in dual porosity simulators is a critical issue. A numerical model of gas-oil gravity drainage was developed and solved analytically for some simple cases and also numerically for more complicated forms of capillary pressure and relative permeabilities. In this article, three famous transfer functions in the literature in a comparative study were checked by a developed numerical model. The result revealed that transfer functions studied here predict less accurate results in comparison with the numerical model and using constant matching parameters cannot resolve this issue because problems arise from simple treatment of time dependent parameters, such as capillary pressure and relative permeability.

  • The influence of pore geometry on the viscous instability in surfactant-polymer flooding in heavy oil reservoirs
    B. Yadali Jamaloei, K. Asghari, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 225-235, Published: 1 February 2015 Informa UK Limited
    This study examines the effect of pore geometry on the viscous instability in surfactant-polymer flooding in an initially preferential water-wet porous medium filled with heavy oil and brine. Two approaches are used to characterize the effect of viscous instability. In both approaches, the dynamic mean pore-scale capillary number is considered as the foremost criterion to characterize the effect of viscous instability. In the first approach, which is a pore network approach, the effect of viscous instability on is neglected. In the second approach, the viscous instability effect is included by using the viscous instability theory to determine . The comparison between from the port network approach and viscous instability theory is used to show the effect of viscous instability. The change in was found to be an appropriate tool to characterize the effect of viscous instability in surfactant-polymer flooding.

  • Asphaltene Instability Trends to Predict Asphaltene Precipitation Onset Pressure: Constrained for Light and Heavy Crude Oils
    Samira Dolati, Hosseinali Zarei, and Riyaz Kharrat

    Journal of Dispersion Science and Technology, ISSN: 01932691, eISSN: 15322351, Pages: 103-110, Published: 2 January 2015 Informa UK Limited
    The study investigates asphaltene instability trends (ASISTs), originally developed by New Mexico Tech, for crude oils with different °API gravities and asphaltene contents. Different ratios of precipitants/solvents have been used to construct the ASISTs at ambient conditions. Results were extended to reservoir conditions using routine PVT data. The ASIST method was used to predict the asphaltene precipitation onset pressure at reservoir conditions. Due to the kinetic effect on asphaltene precipitation using the titration method, pressure depletion induced asphaltene precipitation experiments were carried out for the heavy oil sample. Results, using the modified Miller–Flory–Huggins model, were thermodynamically modeled to validate the ASIST observations and for finding an appropriate lag time that can correspond to reservoir conditions. Similar asphaltene precipitation and thermodynamic modeling were adapted from the literature for the light oil sample. Results suggest that, for the light oil sample, 5 hours is appropriate lag time to perform ASIST, which is in agreement with the reported trends; for the heavy oil sample, however, results suggest that even a 5 hours lag time is not short enough for the titration experiment so that it can be kinetically extended to asphaltene precipitation in the reservoir. We suggest a 1 hour lag time for the samples with low °API gravities and high asphaltene contents. More case studies from different crude oils from different geological settings are required to draw any rigid kinetic framework for the ASIST.

  • Phase trapping effects in viscous-modified low interfacial tension flow during surfactant-polymer flooding in heavy oil reservoirs
    B. Yadali Jamaloei, R. Kharrat, K. Asghari, and F. Ahmadloo

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 139-148, Published: 17 January 2015 Informa UK Limited
    This study examines the effects of non-wetting phase trapping in viscous-modified low-interfacial tension flow during viscous surfactant waterflooding (or surfactant-polymer flooding) under three different injection flowrates in three initially preferential water-wet porous media (each with a different pore throat size) partially filled with heavy oil and brine. In two approaches developed in this study, dynamic mean pore-scale capillary number Nc1 is considered as the foremost criterion to characterize the effect of non-wetting phase trapping. In the first approach, which is a pore network approach, the effect of phase trapping on the value of Nc1 is neglected. In the second approach, which is a numerical method, the effect of phase trapping is included. By comparing the values of Nc1 from the pore network approach and numerical method, the effect of phase trapping is characterized. The change in Nc1 was found to be an appropriate tool to characterize the effects of phase trapping in viscous surfactant waterflooding.

  • Evaluation of vapour extraction process and its prospect as an enhanced oil recovery method
    Ali Esfandyari Bayat, Radzuan Junin, Riyaz Kharrat, and Shahab Hejri

    International Journal of Oil, Gas and Coal Technology, ISSN: 17533317, eISSN: 17533309, Pages: 394-421, Published: 2015 Inderscience Publishers
    The vapour extraction (VAPEX) process is a promising technique to extract heavy oil and bitumen while minimising environmental pollution and capital costs compared to conventional thermal processes. This paper comprehensively reviews the literature on the vapour extraction process to elucidate why VAPEX is not yet operational at the field scale. It was found that unfeasibility of the VAPEX process is mainly attributed to operational issues. A sufficient number of parameters that are associated with these two issues and affect the VAPEX process are evaluated in this paper. [Received: March 11, 2013; Accepted: October 17, 2013]

  • Worm-like micelles: A new approach for heavy oil recovery from fractured systems
    Amir Kianinejad, Milad Saidian, Marzieh Mavaddat, Mohammad Hossein Ghazanfari, Riyaz Kharrat, and Davood Rashtchian

    Canadian Journal of Chemical Engineering, ISSN: 00084034, eISSN: 1939019X, Pages: 951-958, Published: 1 May 2015 Wiley
    In this work, a new type of flooding system, “worm-like micelles”, in enhanced heavy oil recovery (EOR) has been introduced. Application of thesetypes of surfactants, because of their intriguing and surprising behaviour, is attractive for EOR studies. Fundamental understanding of the sweepefficienciesaswellasdisplacementmechanismsofthisfloodingsysteminheterogeneoussystemsespeciallyforheavyoilsremainsatopicofdebatein the literature. Worm-like micellar surfactant solutions are made up of highly flexible cylindrical aggregates. Such micellar solutions display highsurfaceactivityandhighviscoelasticity,makingthemattractiveinpracticalapplicationsforEOR.Inthisstudy,worm-likemicellarsolutionswereusedfor flooding experiments in micromodels, initially saturated with heavy crude oil. The fractured micromodels with different fracture geometricalproperties, different orientation angles and length, were used in the tests under oil-wet condition. During experiments, high quality pictures ofinjection processes were recorded. Oil recoveries as a function of injected pore volumes and microscopic mechanisms during displacements wereinvestigated from precise analyses of the provided pictures. It was observed that three mechanisms govern the EOR process during worm-likemicellar solution flooding: ultra-low interfacial tension, high viscosity of the injecting fluid and in situ formation of macro-emulsion. Consideringthese mechanisms, worm-like micellar surfactants solutions are potentially good choices for EOR in heterogeneous systems such as fracturedreservoirs. This study illustrates that the application of worm-like micelles for heavy oil recovery in heterogeneous systems can reduce the risksinvolved with heterogeneity on flooding performance in such reservoirs.Keywords: worm-like micelles, EOR, heavy oil, micromodel, fracture geometrical properties

  • An experimental and simulation study of heavy oil recovery by the liquid CO 2 huff and puff method
    I. Ekhlasjoo, M. Vosoughi, S. R. Shadizadeh, R. Kharrat, and M. H. Ghazanfari

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2587-2594, Published: 2 December 2014 Informa UK Limited
    In this article a series of experiments were performed to demonstrate the effect of carbon dioxide injection pressure on a huff and puff process. The experimental data are used in a lab-scale model simulated with a commercial simulator to investigate the effect of soaking time, injection pore volume, and rate of injection on the heavy oil recovery. The result of experiments showed that a huff and puff process under miscible pressure conditions gives the most recovery. Simulation results illustrated that there is an optimum value for soaking time, which, for soaking times less than this value, recovery increases and for values greater than optimum the recovery decreases. The simulation study demonstrated that oil recovery increases with increasing volume of injected miscible fluid and recovery decreases with injection rate increase.

  • Integration of LSSVM technique with PSO to determine asphaltene deposition
    Ali Chamkalani, Sohrab Zendehboudi, Alireza Bahadori, Riaz Kharrat, Reza Chamkalani, Lesley James, and Ioannis Chatzis

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 124, Pages: 243-253, Published: December 01, 2014 Elsevier BV
    Abstract Asphaltene deposition is a recognized phenomenon in petroleum industry with undesirable outcomes so that it may lead to wellbore plugging and formation damage, resulting in a large amount of remedial costs to decrease its negative impacts on oil production. Therefore, it has attracted lots of research interests in the literature. In this study, an attempt is made to introduce the least square support vector machine (LSSVM) for prediction of asphaltene deposition. This technique with high capabilities which captures the complex nature of asphaltene could be inferred as a scaling model. As there is no a standard procedure to determine the main parameters of the LSSVM model, the particle swarm optimization (PSO) technique is employed to synchronously optimize the LSSVM parameters. The modeling results clearly demonstrate that the optimized LSSVM is able to handle the nonlinearities well and attain satisfactory results. The comparison of available predictive equations for asphaltene deposition confirms that the LSSVM technique linked with PSO exhibits higher robustness and greater precision with an R 2 of 0.989 for the testing phase.

  • A comparison of natural depletion and different scenarios of injection in the reservoir from the beginning of oil production
    Y. Ahmadi, M. Hasanbaygi, and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 2559-2565, Published: 26 November 2014 Informa UK Limited
    This research comprises natural depletion, associate, and CO2 gas injection with regard to asphaltene precipitation and permeability reduction. For the sake of achievement these goals experiments were undertaken by core flood and asphaltene static apparatus. Natural depletion was performed at 4500, 3050, 2250, 1450, and 900 Psig and it has been seen maximum amount of asphaltene precipitation located at saturation pressure. The results demonstrate that asphaltene precipitation during natural depletion was higher than CO2 and associate gas injection. Also it was seen asphaltene precipitation rate during CO2 and associate gas injection was lower than natural depletion. Based on results, amount of asphaltene precipitation was differing according to type of gas. The results of the study indicate asphaltene precipitation during CO2 injection was more than associate gas injection. Finally it was seen the permeability reduction during associate was less than CO2 and natural depletion for this kind of Iranian carbonate sample.

  • Time-scale space: A new domain for reservoir properties characterization
    M. B. Shahvar, N. D. Badounak, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2113-2125, Published: 2 October 2014 Informa UK Limited
    Logs data are valuable information that, if well interpreted, can provide useful knowledge about the petrophysical properties of the reservoir. In this study, wavelet transform for interpreting logs data are taken into consideration to (1) reveal those aspects of data that cannot be identified easily by normal investigation and (2) characterize the profile of static petrophysical parameters of the reservoir. Obtained results show that gamma ray log has the capability of detecting the flow units' alterations while sonic and resistivity logs well demonstrate the high porosity and permeability zones respectively.

  • A new approach for compressional slowness modeling using wavelet coefficients
    M. B. Shahvar, N. D. Badounak, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2106-2112, Published: 2 October 2014 Informa UK Limited
    Compressional slowness, which may be derived from sonic log, is an important parameter that can be used for determining physical rock properties, such as young modulus and Poisson's ratio. Since the sonic logs are not common in oil fields, modeling the compressional slowness indirectly seems to be a key approach in obtaining the required data for calculating mechanical properties. In this study, a new approach is introduced to construct synthetic models of sonic logs using wavelet coefficients and artificial neural network. Obtained results confirm the applicability of this model in sonic log prediction.

  • Phase behavior modeling of asphaltene precipitation for heavy crude including the effect of pressure and temperature
    M. Tavakkoli, M. H. Ghazanfari, M. Masihi, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2087-2094, Published: 2 October 2014 Informa UK Limited
    Despite numerous experimental and modeling studies, the role of temperature changes on phase behavior modeling of asphaltene precipitation and, in consequence, developing of asphaltene phase envelope in heavy crudes, remains a topic of debate in the literature. In this work, a computer code based on the non-isothermal improved solid model has been developed and used for predicting asphaltene precipitation data for one of the Iranian heavy crudes at different levels of temperature and pressure. The parameters of the non-isothermal model were tuned using three onset pressures at three different temperatures, and the asphaltene phase envelope was developed. The results showed that at high temperatures, increasing the temperature results in a lower amount of asphaltene precipitation and also it causes the convergence of lower and upper boundaries of asphaltene phase envelope. This work illustrates successful application of non-isothermal improved solid model for developing the asphaltene phase envelope of heavy crude.

  • A compositional reservoir simulation and experimental investigation of asphaltene onset pressure
    Y. Ahmadi and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 2253-2262, Published: 17 September 2014 Informa UK Limited
    Asphaltene precipitation is one of the most common problems in many reservoirs and may lead to many safeties operational issues which affects on oil recovery; therefore, identifying start of asphaltene activation is known as a key parameter to control production efficiency. This study includes predicting onset pressure with Multiphase Flash test and compare its result with experimental data generated by Asphaltene Static Apparatus. Safety pressure was obtained by performing Multiphase Flash test for each component. In order to prevent adsorption, mechanical entrapment, and blockage, reservoir pressure must be higher than this safety pressure. SARA test is widely used to identify the fraction of crude oil that affect the asphaltene stability. IP143 standard test was used to measure precipitated asphaltene. Natural depletion test was designed at four steps, including 4400, 3000, 1550, and 1020 Psia and reservoir temperature is 205°F. It was seen that with decreasing pressure from reservoir pressure to saturation pressure asphaltene precipitation from PVT cell was increased and at pressures below saturation pressure with pressure reduction, asphaltene precipitations was decreased. Also it was concluded that above saturation pressure solubility model is dominant and below saturation pressure colloidal model is dominant. The results of IP143 show that initial content of asphaltene are 12.8%. SARA test result shows this kind of fluid located at unstable asphaltene precipitation region. Comparison of safety pressure between Multiphase Flash test and experimental data are investigated and discussed. Onset pressure of 18000 Pisa was obtained from Multiphase Flash test, which is in good agreement with experimental result.

  • The effect of temperature and pressure on the reversibility of asphaltene precipitation
    Y. Ahmadi, R. Kharrat, A. Hashemi, P. Bahrami, and S. Mahdavi

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 2263-2273, Published: 17 September 2014 Informa UK Limited
    A lot of hindrances are seen in petroleum operation, production, and transportation as a results of factors that related to asphaltene precipitation. It has great importance to investigate the reversibility of asphaltene precipitation under changes of effective factors on thermodynamic conditions such as pressure, temperature, and composition. In the present work the reversibility of asphaltene precipitation under changes of pressure and temperature was investigated for two kind of Iranian heavy oil. The stability test shows these samples are located at unstable region in aspect of asphaltene precipitation. The experimental procedure includes two parts, (a) decreasing pressure from initial reservoir pressure to near saturation pressure and surveying asphaltene content hysteresis with redissolution process at reservoir temperature, and (b) investigation of precipitated asphaltene in both precipitation and redissolution processes at different temperature and reservoir pressure. At each step IP143 standard test was used to measure precipitated asphaltene. It was concluded that above bubble point pressure, asphaltene precipitation is nearly reversible with respect to pressure for both samples and it was partially reversible with respect to the temperature for sample A, and accordingly pressurizing is acceptable method for solving the problem in both heavy asphaltenic crude oil samples and increasing temperature is acceptable method for solving asphaltene problem in crude oil sample A. Also density measurement of flashed oil confirmed that there is a little hysteresis in asphaltene content during redissolution and precipitation processes.

  • An experimental investigation of sequential CO2 and N 2 gas injection as a new EOR Method
    M. Rezaei, S. R. Shadizadeh, M. Vosoughi, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1938-1948, Published: 2 September 2014 Informa UK Limited
    Typical non-hydrocarbon gases, which have been utilized in miscible and immiscible processes, are carbon dioxide and nitrogen. These gases are usually injected separately and have been rarely utilized together as a tertiary recovery process. In this article, the authors have experimentally focused on sequential carbon dioxide and nitrogen gas injection as a new enhanced oil recovery method. The periodic injections of carbon dioxide and nitrogen have been repeated for six injection pore volumes. Sensitivity analysis of injection pressure, injection volume, and injection rate has also been investigated in core flood experiments. The experimental results have revealed that a sequential miscible carbon dioxide and immiscible nitrogen gases injection have the highest oil recovery percentage than near miscible or immiscible carbon dioxide and nitrogen injections. The experimental results have shown that increasing ratio of miscible carbon dioxide to nitrogen resulted in increasing ultimate oil recovery percentage. This new method has also been compared with typical enhanced oil recovery methods, namely, water, miscible water-alternating-gas, miscible and immiscible carbon dioxide, and immiscible nitrogen injection using a commercial compositional simulator.

  • Deriving relative permeability from capillary pressure using gaussian and rational equations
    M. B. Shahvar, R. Kharrat, and N. Dashtbesh

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1681-1696, Published: 3 August 2014 Informa UK Limited
    While dynamic data are necessary for a robust reservoir characterization, measuring these type of data in a laboratory is time consuming and very expensive. On the other hand, if dynamic data, especially relative permeability and capillary pressure, are available for discrete grids, they might lead to a more promising simulation model. In the following study, capillary pressure is predicted by artificial neural networks for distinct flow units. Then, two methods are introduced for estimating relative permeability: the first one is based on using Gaussian and rational equations for deriving relative permeability from capillary pressure data and the second one is by utilizing ANN.

  • Experimental and modelling investigations of asphaltene precipitation during pressure depletion and gas injection operations
    H. Nakhli, A. Alizadeh, S. Afshari, R. Kharrat, and M. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1868-1875, Published: 3 August 2014 Informa UK Limited
    Asphaltene precipitation problems manifest themselves in different stages of oil reservoirs production. Experimental and modeling investigations are, therefore, employed as promising tools to assist in predictions of asphaltene precipitation problems and selection of proper production facilities. This study concerns experimental and modeling investigations of asphaltene precipitation during natural production and gas injection operations for a heavy Iranian crude oil at reservoir conditions. First, with design and performance of high pressure–high temperature experiments, asphaltene precipitation behavior is comprehensively investigated; the effects of pressure and temperature are fully studied during pressure depletion tests and the role of injection gas composition on precipitation is described in gas injection experiments. In the next stage, the obtained experimental results are fed into a commercial simulator to develop the asphaltene precipitation model. The results for the pressure depletion experiments indicate that the maximum amount of asphaltene precipitation takes place at fluid bubble point pressure. Increase in the temperature, as seen, causes to reduce the amount of precipitation for the entire range of pressures. For gas injection experiments, the onset of precipitation for CO2, associated, and N2 gases takes place at around 0.20, 0.28, and 0.50 gas to mixture mole ratios, respectively. Carbon dioxide shows the highest asphaltene precipitation values and nitrogen has the lowest amounts for the whole range of gas mole fractions. Finally, the results for modeling indicate successful asphaltene precipitation predictions for both pressure depletion and gas injection processes.

  • Experimental study of asphaltene precipitation behavior during miscible carbon dioxide injection
    A. Alizadeh, H. Nakhli, R. Kharrat, M. H. Ghazanfari, and M. Aghajani

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1523-1530, Published: 18 July 2014 Informa UK Limited
    Many reservoir and production engineers face asphaltene precipitation as a major problem during miscible carbon dioxide flooding projects. Experimental studies regarding asphaltene precipitation are therefore employed to assist in selecting appropriate facilities and proper operation schemes. During this study, a series of high pressure, high temperature experiments are designed and performed to analyze asphaltene precipitation behavior of an Iranian light reservoir crude at reservoir conditions due to natural production and miscible CO2 gas injection. For both sets of experiments, two different temperature levels (including reservoir temperature) are selected to investigate the role of temperature on asphaltene precipitation as well. Results of natural production experiments indicate that the maximum amount of precipitation occurs at reservoir bubble point pressure, while for each specified pressure asphaltene precipitation increases as the temperature is raised for the whole range of pressures. Carbon d...

  • Investigation of the applicability of nano silica particles as a thickening additive for polymer solutions applied in EOR processes
    M. Zeyghami, R. Kharrat, and M. H. Ghazanfari

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1315-1324, Published: 18 June 2014 Informa UK Limited
    In past decades, many attempts have been made to use water-soluble polymers as a mobility control agent to improve sweep efficiency of enhanced oil recovery processes. However, sensitivity of the thickening behavior of these polymers to some harsh conditions, such as high salinity, has cast serious doubt on their applicability in reservoir conditions. By expansion of nanotechnology, scientists discovered that nanoparticles can be utilized as thickening and rheology control agents in many polymer solutions. In this study, hydrophilic fumed silica is added to hydrolyzed polyacrylamide and sulfonated polyacrylamide solutions. The effect of the addition of nano silica on the thickening and stability of the polymer solutions is investigated at different silica and electrolyte concentrations. Augmentation of nano silica has been found to have small but different effects on the thickening behavior of the two polymer solutions. It causes a viscosity increase in sulfonated polyacrylamide solutions while its effect...

  • Monitoring the effect of discontinuous shales on the surfactant flooding performance in heavy oil reservoirs using 2D glass micromodels
    S. Mohammadi, R. Kharrat, M. Masihi, M. H. Ghazanfari, and M. Saidian

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1404-1417, Published: 18 June 2014 Informa UK Limited
    Although most heavy oil reservoirs contain discontinuous shaly structures, there is a lack of fundamental understanding how the shaly structures affect the oil recovery efficiency, especially during surfactant flooding to heavy oils. Here, an experimental study was conducted to examine the effect of discontinuous shales on performance of surfactant flooding by introducing heterogeneities to represent streaks of shale in five-spot glass micromodels. Results show that oil recovery in presence of shale streak is lower than in its absence. Based on the authors’ observations, the presence of flow barriers causes premature breakthrough of injected fluids and also an unstable displacement front. As well, displacement efficiency of surfactant flooding is dependent strongly on the shale distribution configuration. Increasing shale content causes reduction of ultimate oil recovery and also severe fingering during water flooding while it compensates during surfactant flooding considerably. In shaly patterns, in the ...

  • An investigation of inhibitors performance on asphaltene precipitation due to CO 2 injection
    M. A. Karambeigi and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1327-1332, Published: 3 June 2014 Informa UK Limited
    In a CO2 gas displacement process, the injected CO2 can disturb the reservoir fluid stability and induce flocculation and deposition of asphaltenes. Several procedures are used to remove or prevent asphaltene precipitation, but the uses of asphaltene inhibitors provide most practical and economical solution for deposits treatment. In this work, the results obtained on the inhibition effect of one commercial inhibitor namely IR95 and five non-commercial inhibitors namely benzoic acid, nonylphenol, phenanthrene, phthalic acid, and salicylic acid is presented. Static tests indicate that CO2 concentration and temperature are the most important factors on which the asphaltene precipitation depended. Results of inhibitor tests reveal that IR95 with more than 50% precipitation reduction have best efficiency among other inhibitors.

  • An investigation of inhibitors performance on asphaltene precipitation due to associated gas injection
    M. A. Karambeigi and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1213-1218, Published: 19 May 2014 Informa UK Limited
    The nature and behavior of asphaltene in crude oils is complex and changes in temperature, pressure, and composition of crude oils during production can result in precipitation of asphaltene components. Potential solutions for these problems include physical removal of deposits, solvent washes, and treatment with dispersant agents. The authors summarize the results obtained on the inhibition effect of one commercial inhibitor namely IR95 and five non-commercial inhibitors namely benzoic acid, nonylphenol, phenanthrene, phthalic acid, and salicylic acid. The results revealed distinct mechanisms for asphaltene solubilization/dispersion and inhibition of asphaltene precipitation in crude oil and show that IR95 have the best efficiency on precipitation reduction this crude.

  • A core scale investigation of Asphaltene precipitation during simultaneous injection of oil and CO2: An experimental and simulation study
    H. Bagherzadeh, D. Rashtchian, M. H. Ghazanfari, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1077-1092, Published: 19 May 2014 Informa UK Limited
    Although CO2 injection significantly increases the amount of oil recovered, it can cause asphaltene deposition in oil reservoirs. Asphaltene deposition leads to formation damage, in which treatment is a costly and problematic operation. In this work, impact of asphaltene precipitation and deposition during CO2 injection are investigated for recombined oil both in sandstone and carbonate core samples through dynamic flow experiments. Injection of oil and CO2 was performed simultaneously. Then, pressure drops along the core were recorded continuously to estimate permeability reductions during the experiments. Online viscosity of injected fluid was measured by a designed capillary viscometer. Damaged permeabilities were calculated using Darcy equation from the pressure drops and measured viscosity data. The results show that permeability reduction behavior is completely different in sandstone and carbonate core samples. A core scale simulation study with tuned equation of state parameters was carried out to ...

  • An approach for the estimation of dynamic imbibition capillary pressure curves
    M. Shojaadini Ardakany, S. R. Shadizadeh, M. Masihi, R. Kharrat, and M. H. Ghazanfari

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1007-1017, Published: 3 May 2014 Informa UK Limited
    Capillary pressure is one of the most important parameters for reservoir engineering studies. Although different experimental methods are devised to measure capillary pressure, these methods do not represent the physics of fluid flow, which happens at reservoir conditions. Thus, it is attempted to extract the capillary pressure from spontaneous imbibition data, the common mechanism of oil production in water wet porous media. In this work, a new approach is developed to obtain the imbibition capillary pressure curve by using spontaneous water imbibition data in oil-water-rock systems. Comparison of calculated imbibition capillary pressure curves by the new approach with experimental values shows a good accordance with each other.

  • The impact of silica nanoparticles on the performance of polymer solution in presence of salts in polymer flooding for heavy oil recovery
    Ali Maghzi, Riyaz Kharrat, Ali Mohebbi, and Mohammad Hossein Ghazanfari
    ISSN: 00162361, Volume: 123, Pages: 123-132, Published: 1 May 2014 Elsevier BV
    Abstract Due to role of polymer in increasing sweep efficiency during oil recovery, much attention has been paid to the using polymer solutions in enhanced oil recovery methods. In spite of the existence of the great researches in this area, the role of nanoparticles in modification of the polymer performance in the presence of salts has not been examined before. Furthermore, there is no information about how the dispersed silica nanoparticles affect the heavy oil recovery during the polymer flooding in the presence of divalent cations. In this study, a series of polymer flooding experiments are performed in a quarter five-spot glass micromodel saturated with heavy oil. Solutions of polyacrylamide and dispersed silica nanoparticles in polyacrylamide (DSNP) with different salinities are used as the injectants to examine the effect of silica nanoparticles on the polyacrylamide performance in the presence of salts during polymer flooding of heavy oil, the oil recovery values were measured in different salinities. Furthermore, viscosity measurements are performed to help analyzing the results of polymer flooding tests. The oil recovery is measured via analysis of the continuously captured images during the displacement. Also, microscopic monitoring is used to analyze the distribution of residual heavy oil and polymer solution at the pore level. The results showed that the oil recovery decreases by increasing the salt concentration during the polyacrylamide flooding whereas in case of flooding with suspension of silica nanoparticles in polyacrylamide, decreasing rate in oil recovery is lower. The results of viscosity measurements showed that increasing the salt concentration lowers the viscosity of polyacrylamide solution to a minimum value which at higher values salts had a reverse effect and increased solution viscosity. Moreover, viscosity of silica nanosuspension in polyacrylamide was higher than that of polyacrylamide solution at the same salinity. This increase in viscosity becomes more noticeable by increasing the silica nanoparticles concentration. Finally oil recovery values versus injectant viscosity were plotted for different condition of salinity which confirmed the previous results, it means oil recovery was increased wherever injectant viscosity has been increased.

  • A pore-level investigation of surfactant-crude oil displacements behavior in fractured porous media using one-quarter five spot micromodels
    A. Kianinejad, D. Rashtchian, M. H. Ghazanfari, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 727-737, Published: 3 April 2014 Informa UK Limited
    Despite numerous studies, there is a lack of fundamental understanding about the displacement behavior of surfactant-crude oil systems under the influence of different fractures' geometrical properties in five-spot systems. In this work, a series of flow visualization experiments were carried out on one-quarter five spot glass micromodels at various fractures' geometrical properties, such as fracture density and fracture continuity, under oil-wet condition. The influences of injection of Linear Alkyl Benzene Sulfonate and Sodium Dodecyl Sulfate surfactants as well as the effect of fracture geometrical parameters, on macroscopic and microscopic displacement behavior have been investigated. The micromodels were initially saturated with crude oil. Precise analyses of the high quality pictures, which were taken during experiments, were used to explore the surfactant's displacement efficiency. It has been found that two mechanisms govern such a process at the pore scale. One is responsible for decreasing the r...

  • Experimental investigation and modeling of permeability impairment mechanisms due to asphaltene precipitation under CO2 injection conditions
    H. Bagherzadeh, M. H. Ghazanfari, R. Kharrat, and D. Rashtchian

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 591-604, Published: 19 March 2014 Informa UK Limited
    The injection of hydrocarbon gases/CO2 for enhanced oil recovery can promote asphaltene precipitation and consequently reservoir impairment, of which its impact is tremendous. In this work, the results of flow dynamic tests performed on sandstone as well as carbonate rocks were presented. The permeability reduction mechanisms were investigated during simultaneously injection of CO2 and recombined oil into core samples through a static mixer at reservoir conditions. The permeability impairment data was monitored from analysis of recorded pressure and online viscosity measurements during the experiments. Analysis of obtained results revealed that for both sandstone and carbonate rocks, surface deposition and pore plugging mechanisms participate simultaneously in reduction of permeability in primary injected pore volumes. Therefore, a new permeability reduction model is proposed that considers a combination of surface deposition and pore plugging mechanisms. The results of the new model are in good agreement...

  • Gas analysis by in situ combustion in heavy-oil recovery process: Experimental and modeling studies
    Mohammad-Ali Ahmadi, Mohammad Masumi, Riaz Kharrat, and Amir H. Mohammadi

    Chemical Engineering and Technology, ISSN: 09307516, eISSN: 15214125, Pages: 409-418, Published: March 2014 Wiley
    Enormous efforts have been made to facilitate produced-gas analyses by in situ combustion implication in heavy-oil recovery processes. Robust intelligence-based approaches such as artificial neural network (ANN) and hybrid methods were accomplished to monitor CO2/O2/CO. Implemented optimization approaches like particle swarm optimization (PSO) and hybrid approach focused on pinpointing accurate interconnection weights through the proposed ANN model. Solutions acquired from the developed approaches were compared with the pertinent experimental in situ combustion data samples. Implication of hybrid genetic algorithm and PSO in gas analysis estimation can lead to more reliable in situ combustion quality predictions, simulation design, and further plans of heavy-oil recovery methods.

  • Global Dynamic Harmony Search algorithm: GDHS
    Mohammad Khalili, Riyaz Kharrat, Karim Salahshoor, and Morteza Haghighat Sefat

    Applied Mathematics and Computation, ISSN: 00963003, Volume: 228, Pages: 195-219, Published: 1 February 2014 Elsevier BV
    This paper presents a new modification of Harmony Search (HS) algorithm to improve its accuracy and convergence speed and eliminates setting parameters that have to be defined before optimization process and it is difficult to predict fixed values for all kinds of problems. The proposed algorithm is named Global Dynamic Harmony Search (GDHS). In this modification, all the key parameters are changed to dynamic mode and there is no need to predefine any parameters; also the domain is changed to dynamic mode to help a faster convergence. Two experiments, with large sets of benchmark functions, are executed to compare the proposed algorithms with other ones. In the first experiment, 15 benchmark problems are used to compare the proposed algorithm with other similar algorithms based on the Harmony Search method and in the second experiment, 47 benchmark problems are used to compare the performance of the GDHS with other algorithms from different families, including: GA, PSO, DE and ABC algorithms. Results showed that the proposed algorithm outperforms the other algorithms, considering the point that the GDHS does not require any predefined parameter.

  • An experimental study of the matrix-fracture interaction during miscible displacement in fractured porous media: A micromodel study
    M. Saidian, M. Masihi, M. H. Ghazanfari, R. Kharrat, and S. Mohammadi

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 259-266, Published: 2014 Informa UK Limited
    During miscible displacements in fractured porous media, one of the most important factors that plays a significant role in oil production is the matrix-fracture interaction. In this work, a series of hydrocarbon injection experiments have been performed on a fractured glass micromodel that was designed specifically to study matrix-fracture interaction. A high quality image analysis method was used to determine the fluid flow behavior, solvent front movement, and viscous fingering associated with solvent movement in matrix and fractures. Observations showed that in the case of unit viscosity ratio, the injection rate increased the slope of recovery curve and consequently improved the final oil recovery. However, when using a viscosity ratio of 65, the injection rate increased the oil recovery at earlier times due to the breakthrough and fracture drainage. At later times, diffusion and dispersion became dominant and oil recovery decreased. Studying the effect of molecular diffusion revealed that by using a...

  • Asphaltene precipitation during different production operations
    M. A. Karambeigi and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1655-1660, Published: 2014 Informa UK Limited
    Asphaltene precipitation due to enhanced oil recovery (EOR) methods or natural depletion is a serious technical problem at petroleum industry. The authors present the result of asphaltene precipitation during associated gas injection, CO2 injection, and natural depletion in reservoir condition. In addition, the effect of variations in operation pressure, injection gas concentration, and production rate on asphaltene precipitation and difference between slope of precipitation graph due to various method of EOR or natural depletion were investigated. The results revealed that temperature has an efficient role on result of asphaltene deposition through associated gas and CO2 injection. By decreasing temperature, the amount of asphaltene precipitation due to associated gas injection was increased. In fact, recovery of gas injection was decreased at lower temperatures, hence; solubility has an important rule on asphaltene precipitation.

  • Fracture capillary pressure based on the liquid bridge dynamic stability study
    R. Miri, S. R. Shadizadeh, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2536-2545, Published: 2 December 2014 Informa UK Limited
    Performance study of gas oil gravity drainage in stacks of overwhelmed blocks in a gas-invaded zone of naturally fractured reservoirs presents difficult challenges to petroleum engineers. It is believed that there exists some degree of block-to-block interaction that may lead to capillary continuity in fractured reservoirs. Effect of such continuity in gravity drainage is much more pronounced as it increases the height of the continuous fluid column in a reservoir and thereby the recovery of oil as height is a key parameter in gravity drainage mechanisms. It has been experimentally proven that liquid or solid bridges in horizontal fracture can contribute to wetting phase transfer across the horizontal fracture, but there is no mathematical model that predicts the probability of such continuity. In this article, a mathematical model developed by using 1-D Navier-Stock for the free surface flow equation and Young-Laplace of capillary for breakage of the stable liquid bridge held between two pairs of support while stretching. The model gives critical length of fracture aperture, which surely provides capillary continuity. Moreover, the developed model shows flow dependency of fracture capillary pressure and predicts a nonzero value for this parameter, while in the past many researchers used zero fracture capillary pressure for history matching of fractured reservoirs.

  • Empirical estimation of uniaxial compressive strength of shale formations
    Mohsen Farrokhrouz, Mohammad Reza Asef, and Riyaz Kharrat

    Geophysics, ISSN: 00168033, eISSN: 19422156, Pages: D227-D233, Published: 2014 Society of Exploration Geophysicists

  • Influences of hydrophilic and hydrophobic silica nanoparticles on anionic surfactant properties: Interfacial and adsorption behaviors
    Mohammad Zargartalebi, Nasim Barati, and Riyaz Kharrat

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 119, Pages: 36-43, Published: July 2014 Elsevier BV
    Abstract Regarding the novel applications of nanoparticles in enhanced oil recovery, the objective of this study is to investigate if nano-sized silica particles have the potential to introduce enhancement in several aspects of surfactant properties particularly its interfacial and adsorption behaviors. Two types of hydrophilic and slightly hydrophobic fumed silica nanoparticles are used in conjunction with sodium dodecyl sulfate. Extensive series of interfacial tension and adsorption measurement experiments are performed. The results indicate that surfactant interfacial and adsorption properties are interestingly influenced by the addition of silica particles. Inclusion of both nanoparticles into surfactant solution causes contrasting interfacial behaviors in low and high surfactant concentrations. The adsorption of surfactant molecules on the rock surface is generally reduced in the presence of nanoparticles except for some highly concentrated surfactant solutions.

  • Numerical aspects of the convection-dispersion equation
    K. Kamalyar, R. Kharrat, and M. Nikbakht

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1729-1762, Published: 2014 Informa UK Limited
    Virtually all reservoir simulators obtain solutions to fluid flow equations, usually nonlinear partial-differential equations, by making discrete approximations to derivatives. Whether finite-difference or finite-element methods are used, these approximations always introduce truncation errors that often can distort the accuracy and stability of the solution. The truncation error is often referred to as numerical dispersion because, to the lowest order, it can be represented as a second spatial derivative term added to any true dispersion term in the problem. Distortion of the numerical solution is most significant in the simulation of enhanced oil recovery (EOR) processes where sharp displacement, concentration, and/or temperature fronts are an important part of the efficiency of the processes, and artificial smearing as a result of numerical dispersion can render the simulation meaningless. In this work, two different methods, namely, finite difference and method of line, are considered to investigate numerical dispersion. The effect of grid sizes on smearing and oscillation is investigated by selecting various values for grid size. The results indicate that numerical dispersion can be minimized using the method of line as a solution method for the general difference equation.

  • Asphaltene Instability Trends of Light and Heavy Crude Oils
    Samira Dolati, Hosseinali Zarei, and Riyaz Kharrat

    Journal of Dispersion Science and Technology, ISSN: 01932691, eISSN: 15322351, Pages: 970-983, Published: July 2014 Informa UK Limited
    In this work, two Iranian crude oils diluted in 1-methylnaphthalene (1-MN) were titrated with selected n-alkanes. Subsequently, samples were observed microscopically to determine the onset of asphaltene precipitation. A series of micrographs from de-asphaltening were used to show visible changes of the asphaltene sizes, shapes, and frequencies by addition the n-heptane to the subsamples after 5, 6, 11, and 24 hour lag times. The refractive indices (RI) of the titrated mixtures at different temperatures below and above the onset conditions were measured aiming to establish the asphaltene instability trend. Results show that for the diluted light and heavy crude oils, the onset of asphaltene precipitation is rather a gradual process with an almost constant slope of RI decrease due to the separation of asphaltene clusters from the mixture. This is a kinetically controlled process. Furthermore, the nature of the precipitant is likely to play a notable role. The rate of RI decreasing with temperature was appro...

  • Modeling of steam distillation mechanism during steam injection process using artificial intelligence
    Amin Daryasafar, Arash Ahadi, and Riyaz Kharrat

    Scientific World Journal, ISSN: 23566140, eISSN: 1537744X, Volume: 2014, Published: 2014 Hindawi Limited
    Steam distillation as one of the important mechanisms has a great role in oil recovery in thermal methods and so it is important to simulate this process experimentally and theoretically. In this work, the simulation of steam distillation is performed on sixteen sets of crude oil data found in the literature. Artificial intelligence (AI) tools such as artificial neural network (ANN) and also adaptive neurofuzzy interference system (ANFIS) are used in this study as effective methods to simulate the distillate recoveries of these sets of data. Thirteen sets of data were used to train the models and three sets were used to test the models. The developed models are highly compatible with respect to input oil properties and can predict the distillate yield with minimum entry. For showing the performance of the proposed models, simulation of steam distillation is also done using modified Peng-Robinson equation of state. Comparison between the calculated distillates by ANFIS and neural network models and also equation of state-based method indicates that the errors of the ANFIS model for training data and test data sets are lower than those of other methods.

  • Experimental and simulation study of in-situ combustion process in carbonate fractured porous media
    Mohammadali Shojaiepour, Riyaz Kharrat, Mohammadamin Shojaiepour, and Abdonnabi Hashemi

    Journal of the Japan Petroleum Institute, ISSN: 13468804, eISSN: 1349273X, Pages: 208-215, Published: 2014 Japan Petroleum Institute

  • Analysis of diffusivity equation using differential quadrature method
    Romanian Journal of Physics, ISSN: 1221146X, Issue: 3-4, Pages: 233-246, Published: 2014

  • Generation of Asphaltene Deposition Envelope Using Artificial Neural Network
    Vahid Chalangaran, Hamed Firoozinia, Riyaz Kharrat, and Navid Chalangaran

    Journal of Dispersion Science and Technology, ISSN: 01932691, eISSN: 15322351, Pages: 313-321, Published: March 2014 Informa UK Limited
    The usefulness of the asphaltene deposition envelope (ADE) is that no asphaltene flocculation occurs at conditions outside the envelope. Since artificial neural network (ANN) is best at identifying patterns or trends in data, it is well suited for prediction or forecasting needs. ANN is also capable of addressing case specific problems that may be encountered in the field such as deposition of asphaltene. In this article, the high pressure, high temperature setup used to perform pressure depletion experiments at three different temperatures on one the Iranian live oils and the ADE generated using ANN.

  • Asphaltene laboratory assessment of a heavy onshore reservoir during pressure, temperature and composition variations to predict asphaltene onset pressure
    Peyman Bahrami, Riyaz Kharrat, Sedigheh Mahdavi, Yaser Ahmadi, and Lesley James

    Korean Journal of Chemical Engineering, ISSN: 02561115, Pages: 316-322, Published: 2014 Springer Science and Business Media LLC
    An Iranian heavy oil reservoir recently encountered challenges in oil production rate, and further investigation has proven that asphaltene precipitation was the root cause of this problem. In addition, CO2 gas injection could be an appropriate remedy to enhance the production of heavy crudes. In this study, high pressure-high temperature asphaltene precipitation experiments were performed at different temperatures and pressures to investigate the asphaltene phase behavior during the natural depletion process and CO2 gas injection. Compositional modeling of experimental data predicted onset points at different temperatures which determine the zone of maximum probability of asphaltene precipitation for the studied heavy oil reservoir. Also, the effect of CO2 gas injection was investigated as a function of CO2 concentration and pressure. It was found that a CO2-oil ratio of 40% is the optimum for limiting precipitation to have the least formation damage and surface instrument contamination.

  • Rheological behavior of nanosilica suspensions and the potential to enhance polymer flooding performance
    Nasim Barati, Mohammad Zargartalebi, and Riyaz Kharrat

    Special Topics and Reviews in Porous Media, ISSN: 21514798, eISSN: 2151562X, Pages: 327-337, Published: 2013 Begell House

  • An experimental feasibility study of in-situ nano-particles in enhanced oil recovery and heavy oil production
    K. Pourabdollah, A. Zarringhalam Moghaddam, R. Kharrat, and B. Mokhtari

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2198-2208, Published: 2 December 2013 Informa UK Limited
    The influence of nanoclays on the asphaltene deposition, the recovery factor, and the solvent consumption of Iranian heavy oil were studied in a vapor extraction process. Experimental setup consisted of two visual sand-packed cells that were packed, one only with glass-beads as oil matrix and the other with glass-beads and modified montmorillonite as nanoclay, while they had similar porosity and permeability. The analysis of variance on simulated, conventional, and nano-assisted vapor extraction processes showed that nanoclays are able to change the matrix heterogeneity. The high content of precipitated asphaltenes in nano-assisted matrix demonstrated that asphaltenes were adsorbed into the nanoclays, dominantly, and distribution of asphaltene showed a reduction in their facial concentration from the injection port to the oil production port in both cells. The results revealed that the nanoclays increase the dissolved efficiency of solvent and the recovery factor by 30(±4)% in all three replicated experim...

  • A comparison of WAG and SWAG processes: Laboratory and simulation studies
    P. Heidari, R. Kharrat, N. Alizadeh, and M. H. Ghazanfari

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2225-2232, Published: 2 December 2013 Informa UK Limited
    The use of water-alternating-gas injection can potentially lead to improved oil recovery from the fields; simultaneous water and gas injection is a form of water-alternating-gas injection. However, there is still an incomplete understanding of these processes and the need for comparative work is inevitable. Core flood experiments and compositional simulations of water-alternating-gas and simultaneous water and gas processes are presented. Immiscible, near miscible, and miscible modes of injection are covered. Matching process is done and optimization of design parameters (injection rate, slug size, water-alternating-gas ratio, and injection gas) is performed. Experimental data demonstrate that simultaneous water and gas injection accelerate oil production as compared to water-alternating-gas injection in all modes of injection, and miscible simultaneous water and gas injection with CO2 produces more than 74% of original oil in place. The simulation results indicate that with different water-alternating-ga...

  • A case study for HCL-based fracturing and stress determination: A Deformation/Diffusion/Thermal approach
    A.H. Haghi, R. Kharrat, and M.R. Asef

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 112, Pages: 105-116, Published: December 2013 Elsevier BV
    Abstract In this research, attempts were made to estimate the in-situ stresses acting on a hydrocarbon reservoir based on routine activities of acid fracturing in carbonate reservoir. A triple DDT (Deformation/Diffusion/Thermal) full solution was introduced to the estimate maximum horizontal stress magnitude by using rock mechanics and poroelastic equations for the circular underground cavities, fluid diffusivity equation through porous media and thermal stress. To eliminate errors in recognition of the breakdown pressure, it was replaced by re-opening pressure with some modifications. Accordingly, for the first time in this study bilinear flow equation was presented to simulate acid flow through the fracture. Furthermore, this approach was introduced as a good indicator of stress direction in open hole wells while the chemical reaction between HCL-based acids and carbonates caused enlargements of induced fracture and wellbore. Accordingly, this new stress indicator promoted some weaknesses from the old fracturing technologies, such as less fracture initiation pressure by producing heat at the borehole wall, easily defining fractures with caliper and image logs, introducing a triple full solution for direct estimation of S H and so on. This study was then applied successfully to an offshore well, and completed in Triassic carbonate reservoir in Persian Gulf, South Iran. Vertical stress at 2900 m depth was found to be 7800 psi from density log. Maximum and minimum horizontal stresses were calculated by employing the presented method and they were 8730 and 7180 psi respectively. Calculated field stress, noticed fracture and fault's strike direction and maximum horizontal stress orientation worked together and proved strike–slip faulting regime as the present-day stress field. The significance of this approach may be distinguished at both the local and global scale by enabling better correlation and development of in-situ stress data in oil-rich states around the world.

  • Present-day stress of the central Persian Gulf: Implications for drilling and well performance
    A.H. Haghi, R. Kharrat, M.R. Asef, and H. Rezazadegan

    Tectonophysics, ISSN: 00401951, Volume: 608, Pages: 1429-1441, Published: 26 November 2013 Elsevier BV
    Abstract The present-day state of stress in the Persian Gulf is poorly understood but has significant impacts on well drilling and performance. The upper Permian to lower Triassic formation of Kangan/Dalan, Persian Gulf, exhibits a complex structural context in the neighborhood of the Oman Mountains and the Zagros orogenies. This formation is divided into four reservoir layers (K1 to K4) where three main lithologies (limestone, dolomite and anhydrite) are alternating. We conduct an analysis of the present-day stress and natural fractures at the wellbore using full-bore FMI logs, leak off test and density logs. For this purpose, borehole breakout and tensile fracture data are used to determine orientation of S H . Furthermore, density log, leak-off test and Kirsch equation for tensile fracture formation in the wellbores are used to calculate the magnitude of S v , S h and S H , respectively. Vertical stress (S v ) gradient at 3100 m depth approximates 20 MPa/km (2.9 psi/m), indicating a bulk density of 2.04 g/cm 3 . A total of 131 drilling induced tensile fractures and 21 breakouts with an overall length of 262 m are observed in two wells, indicating a mean maximum horizontal stress (S H ) orientation of N53° (± 18.45°) for drilling-induced tensile fracture (DITF) data and N50° (± 10.79°) for breakout data. The mean orientation of S H rotates counterclockwise with depth from K2 (N70° ± 4.2°) to K4 (N40° ± 5.1°) reservoirs. Noticed correlation between these data and stress orientations from earthquake focal mechanism solution, first of all, indicates that the stresses are linked to the resistance forces generated by the Arabia–Eurasia collision at the Zagros orogeny and secondly confirms the reliability of focal mechanism solution data near continental collision zones. In the Kangan/Dalan Formation, the NW–SE main open fracture direction is found as a common regional direction which is sub-perpendicular to the present-day maximum horizontal stress. Minimum horizontal stress (S h ) gradient in reservoir sections is estimated to be equal to 17 MPa/km (2.5 psi/m). The concluded strike–slip stress regime (S H  > S v  > S h ) in the study area is consistent with the compressive regime in the Zagros thrust–fold belt. The present-day stress in the Kangan/Dalan Formation has implications for wellbore stability, lost circulation and well Inflow Performance Relationship (IPR). Wells are more unstable if deviated toward the S v direction, whereas well productivity and mud loss increase in wells deviated toward S H , which conveys the idea of a strike–slip faulting effect tends to keep the natural fractures open in that direction.

  • An experimental investigation of surfactant flooding as a good candidate for enhancing oil recovery from fractured reservoirs using one-quarter five spot micromodels: The role of fracture geometrical properties
    A. Kianinejad, M. H. Ghazanfari, R. Kharrat, and D. Rashtchian

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1929-1938, Published: 18 October 2013 Informa UK Limited
    Surfactant flooding is known to lower the interfacial tension and, hence, reduces capillary forces responsible for trapping oil. Despite numerous experimental studies, little is known about the role of fracture geometrical properties on oil recovery efficiency during surfactant floods, especially in five-spot systems. In addition, application of sodium dodecyl sulfate for oil recovery in fractured media is not discussed well. In this study, two types of surfactant solutions have been injected into micromodels, which were initially saturated with crude oil, having different length, orientation, and distribution of fractures under oil-wet conditions. Precise analyses of continuously recorded pictures during the experiments were used to determine the oil recovery efficiency. The observations reveals that high penetration of surfactant solutions from fractures into the matrixes perfectly postponed the breakthrough time and increased the oil recovery by sweeping the oil in the matrix. This matrix-fracture inte...

  • An experimental and simulation study of asphaltene-lnduced permeability impairment under natural depletion condition
    SPE - European Formation Damage Conference, Proceedings, EFDC, Pages: 1184-1197, Published: 2013

  • An experimental-based numerical simulation of two phase flow through porous media: A comparative study on finite element and finite difference schemes
    M. Tavakkoli, R. Kharrat, and M. H. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1881-1890, Published: 17 September 2013 Informa UK Limited
    In this study, the nonlinear partial differential equations governing two phase flow through porous media are solved using two different methods, namely, finite difference and finite element. The capillary pressure term is considered in the mathematical model. The numerical results on a 2-D test case are then compared with the experimental drainage process and water flooding performed on a glass type micromodel. Based on the obtained results, finite difference technique needs less computational time for solving governing equations of two phase flow, but findings of this method show less agreement with the experimental data. The finite element scheme was found to be more adequate and its results are matched well with the obtained experimental data.

  • Application of multi-criterion robust optimization in water-flooding of oil reservoir
    Elham Yasari, Mahmoud Reza Pishvaie, Farhad Khorasheh, Karim Salahshoor, and Riyaz Kharrat

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 109, Pages: 1-11, Published: September 2013 Elsevier BV
    Abstract Most of the reported robust and non-robust optimization works are formulated based on a single-objective optimization, commonly in terms of net present value. However, variation of economical parameters such as oil price and costs forces such high computational optimization works to regenerate their optimum water injection policies. Furthermore, dynamic optimization strategies of water-flooding often lack robustness to geological uncertainties. This paper presents a multi-objective while robust optimization methodology by incorporating three dedicated objective functions. The goal is to determine optimized and robust water injection policies for all injection wells. It focuses on reducing the sensitivity to the uncertainty in the model and objective function parameters when no measurement information is assumed to be available. This work also, utilizes a derivative-free Evolutionary Multi-objective Optimization (EMO) procedure in the form of a Non-dominated Sorting Genetic Algorithm (NSGA) which attempts to find a robust Pareto-optimal solution without a priori knowledge of the reservoir dynamic models. Some modifications have been introduced to the original NSGA-II code to handle the constraints of the optimization problem. The comparative test studies clearly demonstrate superiority of the proposed methodology to give optimal robust solutions under geological uncertainties with much less standard deviations and variances. Furthermore, the optimization results demonstrate less sensitivity to the imposed time-varying economical parameters such as operation costs and oil price, revealing non-dependency of the introduced multi-objective functions.

  • Injection efficiency and water loss optimization using streamline simulation in water flooding process
    Mashaallah Bostan, Riyaz Kharrat, and Ali Barjas

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1477-1487, Published: 18 July 2013 Informa UK Limited
    This work has used a novel method for injection efficiency optimization following water flooding management. This method is based on individual streamline simulation ability to describe well allocation factor for injection and production wells. In addition, the well allocation factor can provide the amount of attributed fluid to each injector-producer pair and water loss amount, so it is possible to define injection efficiency. Optimization of injection efficiency is based on increasing the injection rates in efficient injectors and decreasing them in inefficient injectors. In this study, we used streamline simulation for injection efficiency and water loss optimization with the aim of increasing oil recovery. The current study includes two parts. Firstly, we identify well injection rates based on mathematical relationships and, secondly, we increase injection efficiency and oil recovery by decreasing water loss to the aquifer. By using this method and with the same amount of injected water, in the first ...

  • An experimental investigation of water-alternating-CO2 coreflooding in a carbonate oil reservoir in different initial core conditions
    M. Motealleh, R. Kharrat, and A. Hashemi

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1187-1196, Published: 3 July 2013 Informa UK Limited
    Due to the lack of any significant primary recovery mechanism in one of the Iranian oil reservoirs, enhanced oil recovery methods are considered for early stage application because it has been depleted rapidly about 200 Psig by primary recovery. Therefore, the objective of this study was to experimentally investigate the performance of water alternating gas injection of this field. Core samples were drilled out of reservoirs' rock matrix and were cut approximately 11–15 cm long and 3.28 cm in diameter. The live oil used in the experiments has been made by recombination of the stock tank oil with a synthetic gas mixture. All coreflood experiments were conducted using live (recombined) oil at 1,700 psig and a reservoir temperature of 115°F. A total number of four displacement experiments were performed on the cores, including two experiments on secondary wag alternation gas injection and others on tertiary water and gas invaded zones wag alternation gas injections. Prior to each test porosity and permeabili...

  • The proper simulation of free fall gravity drainage in the commercial simulator environment
    O. Bina, R. Kharrat, and S. R. Shadizadeh

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1161-1173, Published: 15 June 2013 Informa UK Limited
    Free fall gravity drainage is one of the most efficient mechanisms identified in the gas-invaded zone of naturally fractured reservoirs. It is believed that gravity drainage could result in very high displacement efficiency. In spite of this importunity, there is a lack of theoretical, experimental, and simulation works on investigation of this recovery process. In this study, a new approach is proposed for simulation of free fall gravity drainage called tank model approach. The commercial numerical simulator could be used as a platform to be able to perform this new approach properly. A simulator is selected as an appropriate environment since its fine grid simulation will lead to obtain the most proper results. The fine grid simulation as a numerical approach includes fewer simplifications comparing with available mathematical modeling and, consequently, the results are more accurate by considering numerical models. As a result, the tank model approach is properly performed for simulating the free fall ...

  • Monitoring the role of fracture geometrical characteristics on fingering initiation/development during heavy oil miscible displacements in fractured porous media
    M. Saidian, M. H. Ghazanfari, M. Masihi, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1129-1139, Published: 15 June 2013 Informa UK Limited
    Finger initiation/development at fluid-fluid interface during miscible floods can cause poor displacement efficiency, which is undesirable in enhanced oil recovery processes. In this work, a series of hydrocarbon injection experiments performed on 5-spot glass micromodels that were initially saturated with the heavy crude oil. The fractured micromodels with different fracture geometrical characteristics were used in the tests. High quality image analysis was applied to determine the fluid flow behavior, solvent front movement, and viscous fingering associated with solvent movement in matrix and fractures. Observations showed that higher solvent dispersion in the fractures rather than matrix in both longitudinal and transversal directions cause the finger behavior to be affected by the fracture geometrical characteristics. It also diminishes and merges the fingers to a unit solvent front by increasing spreading in regions near fractures. Due to the heterogeneity induced by fractures in media, finger tip sp...

  • Porosity and permeability prediction based on computational intelligences as artificial neural networks (ANNs) and adaptive neuro-fuzzy inference systems (ANFIS) in southern carbonate reservoir of Iran
    H. Zargari, S. Poordad, and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1066-1077, Published: 15 May 2013 Informa UK Limited
    Reservoir characterization is a hard-to-do task because of the extremely heterogeneous nature of petroleum bearing formations. Studying different sources of data obtained from underground formations shows that abrupt changes in reservoir rock properties are very commonplace, especially in carbonate formations. Overcoming heterogeneity of reservoir is seemed to be impossible at least with current practices. In addition, obtaining reliable data from every foot for all wells is not feasible because of its high cost as well as being very time-consuming. Porosity and permeability distribution are essential reservoir rock properties to be determined in order to build a reservoir model with acceptable accuracy. Analyzing well test and core data are two reliable sources of porosity and permeability determination. Due to the additional time and cost, coring from all points of formation is not feasible. Therefore another way of defining porosity and permeability distribution should be sought in which a more availab...

  • Experimental analysis of secondary gas injection strategies
    P. Heidari, N. Alizadeh, R. Kharrat, M. Hossein Ghazanfari, and A. S. Laki

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 797-802, Published: 15 April 2013 Informa UK Limited
    CO2 injection is a potentially viable method of enhanced oil recovery for medium oil reservoirs. The authors compare the effect of gas injection strategy (simultaneous water-alternating gas [SWAG], water-alternating gas [WAG], and continuous gas injection [CGI]) on recovery in immiscible, near-miscible, and miscible modes of injection. It has been proved that CGI is not the most efficient injection scenario in oil-wet reservoirs. Miscible and near-miscible core flood tests demonstrated high oil recoveries in all injection strategies due to high capillary numbers achieved as a result of miscibility. The fluid mechanics of floods were discussed using pressure drop data, different mechanics was observed for SWAG, WAG, and CGI and better mobility control of SWAG was proven. Results show that tapering postponed gas breakthrough and less amount of gas was injected using this technique, making tapering favorable economically and operationally. Experiments with different gas–water ratios were performed and the re...

  • Flow regime characterization of the gas-assisted gravity drainage process
    S. E. Sadati and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 629-634, Published: 1 April 2013 Informa UK Limited
    Flow regime characterization is helpful in designing efficient gas injection programs in commercial floods. Lenormand et al.'s (1988) phase-diagram is commonly used for flow regime identification of gravity drainage. Lenormand's phase-diagram was developed using horizontal micro-model displacement experiments, whereas the gas-assisted gravity drainage process is vertical displacement, so Lenormand et al.'s plot is not applicable for gas-assisted gravity drainage floods. Inspection of the recovery plots against dimensionless numbers and physical interpretation of dimensionless groups guide flow regime identification. Oil recovery of the gas-assisted gravity drainage process was calculated by using a black oil simulator at different injection rates and aspect ratios. Flow regime of the gas-assisted gravity drainage process was developed based on gravity number and capillary number at different aspect ratios.

  • Permeability prediction based on hydraulic flow units (HFUs) and adaptive neuro-fuzzy inference systems (anfis) in an iranian southern oilfield
    M. H. Zargari, A. Ferasat, and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 540-549, Published: 1 March 2013 Informa UK Limited
    An accurate description of reservoir is necessary for reservoir simulation and performance prediction. It goes without saying that permeability and porosity are two important fundamental parameters to be known for reservoir characterization. Since it is not conceivable to perform coring operation for any place in a reservoir because of cost and time, different methodologies have been introduced to calculate these parameters from different well logs that are usually available for every well in a reservoir. Hydraulic flow unit (HFU) is one of the practical methods in reservoir simulation. HFU is defined as volume of rock that according to petrophysical and geological properties has similar flow of fluid. The concept of HFU has been developed to integrate geological and petroleum engineering data to estimate permeability in cored zone and then use their result to uncored zone. For estimation of HFUs there are some approaches according to data available that some of these methods are gamma ray, flow zone indi...

  • An experimental investigation of silica nanoparticles effect on the rheological behavior of polyacrylamide solution to enhance heavy oil recovery
    A. Maghzi, A. Mohebbi, R. Kharrat, and M. H. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 500-508, Published: 1 March 2013 Informa UK Limited
    The use of polymer flooding as one of enhanced oil recovery methods has recently increased. The occurrence of high shear rates in reservoir and near well bore through perforation nozzles during polymer flooding cause shear degradation of polymers and therefore polymer viscosity has decreased. Rheological behavior of polymer solution in different conditions of oil reservoir is one of the key factors to develop use of polymer solutions. A few researches are available regarding improving rheological behavior of polymeric solution. In this study, to investigate the effect of nanoparticles on rheological behavior of polymer solutions two samples were prepared: polyacrylamide solution in water and suspension of silica nanoparticles in polyacrylamide solution. The sample viscosities in different shear rates were measured. The best rheology models were developed to state rheological behavior of prepared samples and the measured data were compared to power law model. An increase in the viscosity of the suspension ...

  • An experimental investigation of the effect of fracture dip angle on oil recovery and drainage rate in free fall gravity drainage in fractured reservoirs using a glass micromodel (A pore level investigation)
    N. Zareh, R. Kharrat, and M. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 355-367, Published: 15 February 2013 Informa UK Limited
    Gravity drainage is the main production mechanism in the gas invaded zone in naturally fractured reservoirs. However, there are large ambiguities and complexities, resulting from the dynamic of oil depletion from matrix blocks toward the fracture network. Visualization of drained oil at pore scale using glass micromodels provides the opportunity to better understand the effects of different parameters which might affect oil recovery from fractured reservoirs. In this work a micromodel apparatus generated by laser etching is used to perform some gravity drainage tests on the network patterns. The experiments were performed on double block systems using crude oil. The block to block interactions and the formation and changes of capillary bridges between matrix blocks were visually investigated. A suitable empirical model of gravity drainage is used for the prediction and evaluation of experimental data. The empirical model will be used for sensitivity analysis of fracture dip angle which might affect oil re...

  • A comparative study of compositional grading models in petroleum reservoirs
    M. H. Nikpoor, R. Kharrat, and Z. Chen

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 364-369, Published: 15 February 2013 Informa UK Limited
    Composition of petroleum can vary within a reservoir fluid system, and this variation is critically important to be modeled. In this work, different compositional grading models are compared to predict compositional changes in a reservoir with measured data. The goal is seeking the model that best describes these changes in composition of the reservoir fluid.

  • The scaling of the gas-assisted gravity drainage process using dimensionless groups
    S. E. Sadati and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 164-172, Published: 15 January 2013 Informa UK Limited
    Scaling of the gas-assisted gravity drainage process using inspectional analysis leads to a better understanding of the process. Seven scaling groups were derived by using inspectional analysis for the gas-assisted gravity drainage process and were reduced to five independent dimensionless groups. Based on these five dimensionless groups, a new dimensionless group was proposed for better representing all factors and forces that affect the process. The newly proposed dimensionless group was derived from experimental data in the literature and was validated by using reservoir simulation data. This number that is derived from experimental data in the core scale can predict oil recovery in reservoir scale by some modification in gravity number.

  • The modeling of 3d compositional grading and plus fraction molecular weight change in non-isothermal petroleum reservoirs
    M. H. Nikpoor, R. Kharrat, and Z. Chen

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 99-109, Published: 15 January 2013 Informa UK Limited
    Composition and physical properties vary within hydrocarbon reservoirs, even in well connected ones; it is of crucial interest to model this change in order to initialize the reservoir simulator. In this work, a non-isothermal model is used to depict changes in plus fraction molecular weight and it will be integrated into another non-isothermal model describing fluid compositional changes within a 3D reservoir. Previously, the model has been validated versus 1D real reservoir data. It will be used to model compositional change of real hydrocarbon in a synthetic 3D reservoir subjected to temperature gradient in x, y, and z directions.

  • Anionic surfactant adsorption through porous media in carbonate cores: An experimental study
    A. Gandomkar and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 58-65, Published: 2013 Informa UK Limited
    The phenomenon of surfactant adsorption at solid/liquid interface is of major importance in the process of enhanced oil recovery. The basic objective of this study is to calculate adsorption density and also to model the kinetics of adsorption processes on carbonate rocks. The kinetics adsorption was calculated by examining adsorption behavior in a system of a solid phase (carbonate rock) and an aqueous phase of surfactant with 5,000 ppm synthetic/field brine. The surfactant adsorption on reservoir carbonate rocks was measured to determine the amount of excess surfactant that must be added into the injection stream in the surfactant alternating CO2 injection tests. The adsorption densities were measured by using circulation tests through core samples. The range of initial surfactant concentrations were 500, 1,000, 2,000, and 5,000 ppm in a circulating system. The applied commercial surfactant is sodium lauryl sulphate, which is an anionic surfactant. Finally, the Langmuir adsorption isotherm was used to characterize the equilibria between the amount of adsorbate that accumulates on the adsorbent and the concentration of the dissolved adsorbate. The adsorption process showed that the rate of adsorption is dependent on availability of surfactant in the system. It was found that the adsorption of surfactant increased with increasing surfactant concentration. Also, for the flow-through tests, the necessary equilibrium time was approximately 4 days.

  • Slightly hydrophobic silica nanoparticles for enhanced oil recovery: Interfacial and rheological behaviour
    Mohammad Zargartalebi, Riyaz Kharrat, Nasim Barati, and Ali Zargartalebi

    International Journal of Oil, Gas and Coal Technology, ISSN: 17533317, eISSN: 17533309, Pages: 408-421, Published: 2013 Inderscience Publishers
    This paper is aimed at studying AEROSIL® R816 nanoparticle behaviour to see if it has enough feasibility to be used as a chemical agent in enhanced oil recovery (EOR) processes. The main focus is on interfacial and rheological behaviour of this particle in aqueous and polymeric media. Interfacial tension measurements between aqueous nanoparticle suspensions and oil showed that AEROSIL® R816 particles were able to reduce the interfacial tension between water and oil to half of its original value. This property led to development of stabilised oil in water emulsions. Moreover, viscosity measurements showed that AEROSIL® R816 had a great ability in rheology modification of aqueous solutions. The solution viscosity was studied as a function of nanoparticle concentration and shear rate. It was seen that viscosity rose as the nanoparticle concentration was increased. From the standpoint of shear dependency, two regions of shear thinning behaviour were observed for different shear rate regions. Finally, by dissolving a fixed amount of a low molecular weight polyacrylamide into nanoparticle suspensions of different concentrations, the stability of R816 suspensions was significantly improved. This addition also resulted in almost considerable enhancement of nanoparticle thickening property. (Received: January 15, 2012; Accepted: July 17, 2012)

  • An experimental and modeling study of asphaltene deposition due to CO 2 miscible injection
    H. Bolouri, M. Schaffie, R. Kharrat, M. H. Ghazanfari, and E. Ghoodjani

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 129-141, Published: 2013 Informa UK Limited
    The authors studied deposition and entrainment of asphaltene particles as major mechanisms that occur in porous media. Deposition mechanisms that contribute to permeability reduction and entrainment of deposited particle improve the damaged permeability value. While in most previous works the effects of entrainment mechanism are considered negligible, in this study miscible CO2 injection tests were conducted by core flood apparatus to investigate the effect of asphaltene deposition on permeability and porosity alterations. Results indicated that proposed model for entrainment mechanism is affected by deposition mechanism. The asphaltene deposition core's characteristics have undeniable roles in core impairment.

  • Asphaltene deposition prediction using adaptive neuro-fuzzy models based on laboratory measurements
    Karim Salahshoor, Sepide Zakeri, Sedigheh Mahdavi, Riyaz Kharrat, and Mahmoud Khalifeh

    Fluid Phase Equilibria, ISSN: 03783812, Volume: 337, Pages: 89-99, Published: 2013 Elsevier BV
    Abstract Deposition of asphaltene is recognized as a well-known severe problem, which can significantly affect oil production and enhanced oil recovery processes through mechanism of wettability alteration and blockage. The natural mechanism is not fully comprehended until now due to impossibility to carry out actual field experiments. In this work, different flow dynamic test scenarios are organized to perform on sandstone as well as carbonate rocks to practically explore process of asphaltene deposition. Ordinary optimized methods are not applicable to asphaltene deposition due to its dependency on the involved parameters and complexity of process. The permeability impairment data is monitored through analysis of recorded pressures during the test experiments. Then, a new adaptive neuro-fuzzy inference system is developed to predict asphaltene deposition in terms of permeability ( K / K 0 ) and pressure drop ( DP ), considering pore volume injection (PVI) and time data as input variables. Accordingly, two adaptive neuro-fuzzy models are sequentially developed in a nonlinear affine-type configuration to investigate the effect of multiple variables and parameters on asphaltene deposition on the basis of the most recent input–output data. A series of test studies has been conducted to demonstrate the efficient capabilities of the proposed algorithm to automatically predict asphaltene deposition for different prediction horizons using the online affine-type identified models. Eventually, acceptable agreement between experimental and estimated permeability and pressure drop is investigated to demonstrate superiority of the proposed approach to monitor future asphaltene status that will be useful to prediction of field production under natural depletion process.

  • On the control of glass micro-model characteristics developed by laser technology
    S. Mohammadi, A. Maghzi, M. H. Ghazanfari, M. Masihi, A. Mohebbi, and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 193-201, Published: 2013 Informa UK Limited
    The role of micro-models for studying fluid flow mechanisms at the pore scale is undeniable. Recently, application of laser technology has been much attended for developing micro-models with different flow patterns. However, there is no reported experience in the literature that has been correlated with the laser parameters for direct control of micro-model pore size characteristics. In this work, a CO2 laser device was used to construct flow patterns on the glass surfaces, and the effect of fractional power, engraving speed, and resolution ratio on etched depth as well as surface heterogeneity of constructed models were investigated. A new correlation has been proposed that relates the laser parameters to the pore morphology of the glass micro-models. The proposed exponential expression provides a reasonably accurate and fast tool for controlling micro-model characteristics. In addition, microscopic observation showed that sensible heterogeneity on glass surfaces induced by laser can be controlled by adjusting the resolution ratio, and is a good representation of reservoir rock surfaces. The permeability of the constructed models by a laser device is a better representation of real reservoir rock conditions. The results of this work can be helpful for designing and constructing micro-models with controlling pore morphology.

  • Investigation of effective mechanisms in permeability reduction due to asphaltene deposition through porous media
    SPE - European Formation Damage Conference, Proceedings, EFDC, Pages: 1198-1213, Published: 2013

  • The determination of effective diffusivity coefficients in a solvent gas heavy oil system for methane
    E. Zamanian, M. Dadvar, R. Kharrat, and M. H. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 2582-2593, Published: 15 December 2012 Informa UK Limited
    Abstract In this investigation, an accurate high pressure and temperature diffusion setup was applied to measure the diffusion coefficients of methane in Iranian heavy oils in presence and absence of porous media by using the pressure-decay method. The solvent diffusivity in heavy oil was determined by both graphical and numerical methods. In addition, the effects of the porous medium and the temperature on the molecular diffusion coefficient of the solvent gas in the liquid phase were discussed and finally, using experimental data, a functionality dependence of molecular diffusivity on temperature and porous medium characteristics was proposed.

  • An experimental study on the applicability of water-alternating-co 2 injection in the secondary and tertiary recovery in one iranian reservoir
    M. Motealleh, R. Kharrat, A. Gandomkar, H. Khanamiri, M. Nematzadeh, and M. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 2571-2581, Published: 15 December 2012 Informa UK Limited
    Abstract The objective of this study was to experimentally investigate the performance of water-alternating gas (WAG) injection in one of Iran's oil reservoirs that encountered a severe pressure drop in recent years. Because one of the most appropriate studies to evaluate the reservoir occurs generally on rock cores taken from the reservoir, core samples drilled out of the reservoir's rock matrix were used for alternating injection of water and gas. In the experiments, the fluid system consisted of reservoir dead oil, live oil, CO2, and synthetic brine; the porous media were a number of carbonate cores chosen from the oilfield from which the oil samples had been taken. All coreflood experiments were conducted using live (recombined) oil at 1,700 psi and reservoir temperature of 115°F. A total of four displacement experiments were performed in the core, including two experiments on secondary WAG injection and others on the tertiary water and gas invaded zones WAG injections. Prior to each test porosity and...

  • Phase behavior modeling of asphaltene precipitation for heavy crudes: A promising tool along with experimental data
    M. Tavakkoli, R. Kharrat, M. Masihi, M. H. Ghazanfari, and S. Fadaei

    International Journal of Thermophysics, ISSN: 0195928X, Pages: 2251-2266, Published: December 2012 Springer Science and Business Media LLC
    Thermodynamic modeling is known as a promising tool for phase behavior modeling of asphaltene precipitation under different conditions such as pressure depletion and CO2 injection. In this work, a thermodynamic approach is used for modeling the phase behavior of asphaltene precipitation. The precipitated asphaltene phase is represented by an improved solid model, while the oil and gas phases are modeled with an equation of state. The PR-EOS was used to perform flash calculations. Then, the onset point and the amount of precipitated asphaltene were predicted. A computer code based on an improved solid model has been developed and used for predicting asphaltene precipitation data for one of Iranian heavy crudes, under pressure depletion and CO2 injection conditions. A significant improvement has been observed in predicting the asphaltene precipitation data under gas injection conditions. Especially for the maximum value of asphaltene precipitation and for the trend of the curve after the peak point, good agreement was observed. For gas injection conditions, comparison of the thermodynamic micellization model and the improved solid model showed that the thermodynamic micellization model cannot predict the maximum of precipitation as well as the improved solid model. The non-isothermal improved solid model has been used for predicting asphaltene precipitation data under pressure depletion conditions. The pressure depletion tests were done at different levels of temperature and pressure, and the parameters of a non-isothermal model were tuned using three onset pressures at three different temperatures for the considered crude. The results showed that the model is highly sensitive to the amount of solid molar volume along with the interaction coefficient parameter between the asphaltene component and light hydrocarbon components. Using a non-isothermal improved solid model, the asphaltene phase envelope was developed. It has been revealed that at high temperatures, an increase in the temperature results in a lower amount of asphaltene precipitation and also it causes the convergence of lower and upper boundaries of the asphaltene phase envelope. This work illustrates successful application of a non-isothermal improved solid model for developing the asphaltene phase envelope of heavy crude which can be helpful for monitoring and controlling of asphaltene precipitation through the wellbore and surface facilities during heavy oil production.

  • The tertiary FAWAG process on gas and water invaded zones: An experimental study
    A. Gandomkar and R. Kharrat

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1913-1922, Published: 15 October 2012 Informa UK Limited
    Abstract In this research, experimental investigations of foam-assisted water alternating gas and water alternating gas processes in carbonate cores are studied in order to estimate the increases in the oil recovery in the gas and water invaded zones. Core flooding experiments were performed for low-temperature fractured carbonate cores, chosen from one of the Iranian carbonate oil reservoirs, under tertiary recovery conditions. The experiments were conducted on 1.5-in. diameter carbonate cores, using live oil and synthetic/field brine (with 5,000 ppm of salts) as the water formation and also sodium lauryl sulfate as an anionic surfactant along with pure CO2 as the injection gas. The samples were initially saturated with live oil and connate water and then flooded with brine to reach residual oil saturation at reservoir conditions (115°F and 1,700 psia) to imitate the water invaded zone in the core. In addition to that, since the reservoir has a secondary gas cap, the same procedure was used to provide th...

  • Experimental study of polymer flooding in fractured systems using five-spot glass micromodel: The role of fracture geometrical properties
    Behbood Abedi, Mohammad Hossein Ghazanfari, and Riyaz Kharrat

    Energy Exploration and Exploitation, ISSN: 01445987, Pages: 689-706, Published: 1 October 2012 SAGE Publications
    Water flooding is being widely used in the petroleum industry and has been considered as a simple inexpensive secondary recovery method. But in fractured formations, existence of fracture system in reservoir rock induces an adverse effect on oil recovery by water flooding. Polymer flooding has been successfully applied as an alternative enhanced oil recovery method in fractured formations. But, the role of fracture geometrical properties on macroscopic efficiency of polymer flooding is not yet well-understood, especially in fractured five-spot systems. In this work five-spot glass micromodel, because of micro-visibility, ease of multiple experimentations and also presence of the unexplored issues, was used to experimentally investigate the influence of fracture geometrical characteristics such as fracture orientation, fracture spacing, fracture overlap and etc on the macroscopic efficiency of polymer flooding. The tests were performed on the fractured models which are initially saturated with the crude oil at fixed flow rate conditions and in a horizontally mounting. The results revealed that the macroscopic efficiency of polymer flooding depends on fracture geometrical properties. Fracture orientation showed more imposing effect than other fracture geometrical properties, and fracture with 45 degree inclination to the mean flow direction, gives greatest oil recovery factor. Large spacing fractures give more recovery than small spacing ones and in case of overlapping, fractures with less overlapping help polymer to better propagate which could be related to their greater effective fracture length. This pre-called effect could be responsible to show how continuity and width to length ratio of fractures affect recovery factor, less fracture discontinuity as well as more length to width ratio of fracture give more swept zone. Also, increasing number of fractures decreases oil recovery factor. The results of this work can be helpful to better understanding the role of fracture geometrical properties on macroscopic efficiency of polymer flooding in five-spot fractured systems.

  • Pore-scale description of surfactant-enhanced waterflooding for heavy oil recovery
    Benyamin Yadali Jamaloei and Riyaz Kharrat

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 92-93, Pages: 89-101, Published: August 2012 Elsevier BV
    Abstract This study provides new insights into some pore-scale displacement events occurring in the presence of adverse mobility ratio through mixed-wet porous media with different pore throat sizes. This type of flow is normally created in surfactant-based chemical flooding of heavy oil reservoirs. The experiments were carried out in three etched micromodel networks (each with a different pore throat size) containing oleic phase, aqueous surfactant solution, and connate water film. We discussed the first part of the pore-scale mechanisms and events, which were observed in the micromodel experiments, in Yadali Jamaloei and Kharrat (2011) . Here we present the second part of our analysis of the pore-scale displacement events and the interactions between oleic phase, aqueous surfactant solution, and connate water film in pore networks with different pore throat sizes. Furthermore, some implications for the pore-scale network modeling of this type of flow are discussed. Finally, the effects of pore throat size on the distribution of the pore-scale capillary number and the mean pore-scale Weber number are evaluated.

  • The investigation of suitability of different capillary number definitions for flow behavior characterization of surfactant-based chemical flooding in heavy oil reservoirs
    Benyamin Yadali Jamaloei, Koorosh Asghari, and Riyaz Kharrat

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Volume: 90-91, Pages: 48-55, Published: July 2012 Elsevier BV
    Abstract The surfactant-based chemical flooding can be considered as a suitable method to enhance the oil recovery from some heavy oil reservoirs where thermal and solvent-based methods face some technical and environmental challenges. To properly characterize the microscopic and macroscopic flow behavior of the surfactant-based chemical flooding in heavy oil reservoirs, the interplay between viscous, capillary, and gravitational forces should be identified by utilizing bond and capillary numbers. Unlike bond number (which represents the ratio of gravity-to-capillary force), the capillary number (which represents the ratio of viscous-to-capillary force) has been defined in several forms in the literature. The capillary number should be employed appropriately based on the scale and fluid flow behavior. This study evaluates the suitability of the pore-scale, Newtonian-fluid, and apparent capillary number for the flow behavior characterization of the surfactant-based chemical flooding in heavy oil reservoirs. The results show that the apparent capillary number definition applies to both surfactant-polymer flood (SPF) and surfactant flood (SF), and more accurately represents the dynamics of surfactant-polymer solution in porous media. Thus, for viscous-force-modified systems, such as surfactant-polymer solution and polymer-added fluid floods, the apparent capillary number definition is appropriate to characterize the non-Newtonian behavior in heavy oil reservoirs. In SF, the surfactant solution apparent viscosities are 2–2.5 times greater than the dynamic viscosities and the surfactant solution approaches a Newtonian behavior only at relatively high flow rates when the apparent viscosity tends to approach dynamic viscosity of the surfactant solution. Hence, the Newtonian-fluid capillary number would be valid and can be employed in a region of Newtonian behavior in SF in heavy oil reservoirs.

  • The influence of salinity on the viscous instability in viscous-modified low-interfacial tension flow during surfactant-polymer flooding in heavy oil reservoirs
    Benyamin Yadali Jamaloei, Riyaz Kharrat, and Koorosh Asghari
    ISSN: 00162361, Pages: 174-185, Published: July 2012 Elsevier BV
    Abstract In this study, the effect of viscous instability at varying salinities of the displacing non-wetting phase (i.e., surfactant–polymer solution) in surfactant–polymer flooding of heavy oil reservoirs– which is a viscous-modified low-interfacial tension (IFT) flow through an initially preferential oil-wet porous medium– is quantified in the presence of the adverse mobility ratio. The dynamic mean pore-scale capillary number values are determined using two different approaches. The first approach is a Pore network approach (PNA) that excludes the viscous instability effects. The second approach is using the Viscous instability model (VIM) proposed by Peters and Flock [49] in which the concept of the wavelength of the viscous fingers is introduced. Afterwards, these two dynamic mean pore-scale capillary number values are compared to each other to highlight the effects of viscous instability at different salinity levels of the surfactant–polymer solution. The results show that including the viscous instability effects in the qualitative and quantitative evaluations of the viscous-modified low-IFT flow is vital. In particular, the viscous instability effects become more complex near the breakthrough of the displacing non-wetting phase. Furthermore, the effects of the salinity on the dynamic mean pore-scale capillary number (by excluding/excluding the viscous instability effects, i.e., from PNA and VIM, respectively), IFT, dynamic viscosity, contact angle, displacement front configuration, wavelength of the viscous fingers, dynamic values of the desaturated displaced wetting phase, breakthrough time, and the time of infinite injected pore volume is discussed in the surfactant–polymer flooding of an initially preferential oil-wet porous medium containing heavy oil.

  • Monitoring wettability alteration by silica nanoparticles during water flooding to heavy oils in five-spot systems: A pore-level investigation
    Ali Maghzi, Saber Mohammadi, Mohammad Hossein Ghazanfari, Riyaz Kharrat, and Mohsen Masihi

    Experimental Thermal and Fluid Science, ISSN: 08941777, Pages: 168-176, Published: July 2012 Elsevier BV
    Abstract It is well known that the displacement efficiency of EOR processes is mainly affected by wettability of porous medium; however, the role of nanoparticles on wettability alteration of pores surfaces remains a topic of debate in the literature. Furthermore, a little is known about how the dispersed silica nanoparticles affect the microscopic/macroscopic recovery efficiency of heavy oils during common immiscible EOR processes such as water flooding. In this study, a series of injection experiments was performed on five-spot glass micromodel which is initially saturated with the heavy oil. Distilled water and dispersed silica nanoparticles in water (DSNW) at different values of weight percent were used as injected fluids. The macroscopic efficiency as well as fluid distribution in the pores and throats was monitored from analysis of continuously provided pictures during the experiments. Contact angles of the glass surfaces at different conditions of wettability were measured by using sessile drop method when the glass surfaces coated by heavy oil, distilled water and the solutions of DSNW. The results revealed that the silica nanoparticles caused enhancement of sweep efficiency during water flooding and this enhancement was intensified by increasing the silica nanoparticles percent in water. And also, ultimate efficiency for DSNW (0.1 wt%) flooding increased by a factor of 8.7% in comparison to distilled water flooding. This increment in oil recovery was reached to 26% by increasing silica nanoparticles weight percent from 0.1 wt% to 3 wt%. However, beyond a specific limit of nanoparticles concentration, around 3 wt%, incremental oil recovery declines to some extent. The distribution of DSNW solution during flooding tests in pores and throats showed strong water-wet condition after flooding with high concentration of nanosolution. The results of sessile drop experiments showed that coating with heavy oil, could make an oil-wet surface. While, coating with distilled water could partially alter the wettability of surface to water-wet and coating with high concentration of DSNW could make a strongly water-wet surface. The hydrophilic nature of selected silica nanoparticles, strong hydrogen bonding between silica and water and therefore increment in surface free energy are responsible for wettability alteration of the micromodel from oil-wet to water-wet. Results of this work disclose the effect of silica nanoparticles on wettability alteration of pores surfaces as well as on enhancement of microscopic/macroscopic efficiency during DSNW flooding to heavy oils.

  • Gas assisted gravity drainage by CO 2 injection
    N. Akhlaghi, R. Kharrat, and S. Mahdavi

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1619-1627, Published: 29 June 2012 Informa UK Limited
    Abstract The gas assisted gravity drainage process is designed to take advantage of gravity between the injected gas and reservoir crude oil due to the difference in their densities. In this experimental study, a 2-D Hele-Shaw physical model with dimensions of 15 × 66 × 3 cm was packed with uniform and different sand packs to conduct visual experiments of CO2 injection. These experiments were designed to imitate the dimensionless parameters observed in some field projects. The results show high Bond number lead to high oil recovery because of large absolute permeability. Additionally, the reduction rate of CO2 injection from 50 to 20 cc/min tends to decrease the amount of Capillary number and then increase oil recovery. Comparison between free and forced gravity drainage applying forced gravity drainage was found to be essential with regard to oil recovery.

  • The lessons learned from miscible gas flooding in naturally fractured reservoirs: Integrated studies, and pilot and field cases
    B. Yadali Jamaloei and Riyaz Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1802-1812, Published: 27 June 2012 Informa UK Limited
    Suitable methods have to be employed for secondary and tertiary oil recovery from the naturally fractured reservoirs (NFRs). The miscible gas injection has shown some promising results for enhancing oil recovery from NFRs. However, proper design of the field-scale miscible gas injection projects in NFRs is still a major challenge. The authors evaluate the technical issues of the miscible gas injection in NFRs. The classification of NFRs and their production characteristics, the mechanisms of oil production in NFRs, and significant findings of integrated studies, pilot and field trials, and commercial field projects of the miscible gas injection in NFRs are reviewed. Finally, important issues are identified, which need detailed investigations for the design and performance assessment of the field projects. It is hoped that this paper will serve as a helpful reference for the engineers interested in miscible gas injection process in NFRs.

  • An integrated reservoir characterization analysis in a carbonate reservoir: A case study
    M. Chekani and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1468-1485, Published: 31 May 2012 Informa UK Limited
    Abstract Reservoir characterization is one of the most challenging subjects in carbonate reservoirs. In this study flow zone index (FZI), Winland, and initial water saturation methods were used to classify rock typing in an Iranian oil field. In addition, stratigraphic modified Lorenz plots were generated for the purpose of identifying the flow zone and barriers in each well. The results were consistent with Winland result and FZI. The scanning electron microscopy photomicrographs, pore throat radius, grain size distribution data, and thin section of the obtained rock type were studied and found to be consistent with the findings of this work.

  • Simulation and analysis of production induced reservoir compaction using geomechanical formulation of fracturing technology (GFFT) for stress prediction
    Society of Petroleum Engineers - International Petroleum Technology Conference 2012, IPTC 2012, Pages: 2033-2042, Published: 2012

  • Experimental study of miscible displacement with hydrocarbon solvent in shaly heavy oil reservoirs using five-spot micromodels: The role of shale geometrical characteristics
    Saber Mohammadi, Mohammad Hossein Ghazanfari, Mohsen Masihi, and Riyaz Kharrat

    Journal of Porous Media, ISSN: 1091028X, Pages: 415-427, Published: 2012 Begell House

  • An experimental study of secondary WAG injection in a low-temperature carbonate reservoir in different miscibility conditions
    M. Nematzadeh, H. Khanamiri, M. Aghajani, R. Kharrat, A. Gandomkar, M. Motealleh, and M. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1359-1368, Published: 30 April 2012 Informa UK Limited
    Abstract This experimental study is aimed at evaluation of the performance of secondary WAG injection in carbonate cores at different pressures. To do so, a comprehensive series of high-pressure high-temperature (HPHT) core flooding tests are conducted. The fluid system includes reservoir dead and live crude oil, CO2, and synthetic brine while the chosen porous media consists of a number of fractured carbonate core samples. Parameters such as oil recovery factor, water and oil production rates, and pressure drop along the core are recorded for both dead and live oil. According to results, at first increasing pressure improves the oil recovery, but this improvement after MMP is not as significant as it is before MMP. Also recoveries of dead and live oils at same pressure show different values due to differences in miscibility condition of injected gas. Then as the graphs demonstrate, relative permeability reduction due to hysteresis effect has dominant effect on pressure drop curves. Finally, as the produc...

  • A new approach to the modeling of a simple re-infiltration gravity drainage process in naturally fractured reservoirs
    R. Askarinezhad, R. Kharrat, and S. R. Shadizadeh

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1004-1020, Published: 30 March 2012 Informa UK Limited
    Abstract One of the most important concerns regarding prediction of production performance in naturally fractured reservoirs is the issue of re-infiltration phenomena. In this study, the modeling of a simple re-infiltration process with no effect of capillary continuity between blocks is presented by extending the gravity drainage mechanism for a single block. First, a qualitative analysis of the gravity drainage process through porous media was conducted and the role of gravity and capillary forces was investigated. Then a model for one-dimensional gravity drainage in a single block was developed in dimensionless form, a modified version of which can be found in the literature. Then, using the method of separation of variables, the corresponding partial differential equation was solved for a single block with certain boundary and initial conditions. The upper boundary is a no-feed boundary and at the lower boundary the gas saturation is always zero. At the initial condition, the gas saturation is equal t...

  • An experimental investigation of foam for gas mobility control in a low-temperature fractured carbonate reservoir
    A. Gandomkar, R. Kharrat, M. Motealleh, H. H. Khanamiri, M. Nematzadeh, and M. H. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 976-985, Published: 30 March 2012 Informa UK Limited
    Abstract This work concerns the experimental investigation of surfactant alternating CO2 injection in carbonate rocks. The core samples provided from a low-temperature fractured light oil reservoir, located in southwest Iran. The experiments were designed to observe the effect of CO2–foam injection on gas mobility and oil recovery at different surfactant concentrations. The core samples were initially saturated with synthetic/field brine, 5,000 ppm, and then flooded with live oil to reach connate water saturation at reservoir condition, 115°F and 1,700 psia. The commercial surfactant used was sodium lauryl sulfate as an anionic surfactant. The results of this work, along with field-scale simulation and/or economic considerations, could be helpful in making reliable decisions about optimum condition of foam-assisted water-alternating-gas (FAWAG) processes. Core flooding results demonstrated that macroscopic sweep efficiency increased due to foam generation inside the core. In addition, it led to an increas...

  • Optimization assisted asphaltene deposition modeling in porous media during a natural depletion scheme
    V. Hematfar, M. Bagheri, R. Kharrat, M. Ghazanfari, and C. Ghotbi

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 958-965, Published: 14 March 2012 Informa UK Limited
    Abstract Changes in thermodynamic properties such as pressure, temperature, and composition may result in asphaltene precipitation and deposition in porous media. In addition, asphaltene deposition can cause wettability alteration, permeability reduction, and ultimately a decrease in the productivity of a reservoir. Natural depletion is one of the most common processes of asphaltene deposition in which pressure changes destabilize the dissolved asphaltene in the oil and settle them onto the rock surface. In this work, natural depletion experiments in consolidated core samples were performed under simulated reservoir conditions to obtain reliable data and analyze the asphaltene deposition mechanisms. A mass balance equation, momentum equation, asphaltene deposition, and permeability reduction models were applied to model the process of permeability changes as a result of asphaltene deposition. MATLAB programming language was used to calculate the numerical form of the above equations iteratively. A genetic...


  • An experimental investigation of fracture tilt angle effects on frequency and stability of liquid bridges in fractured porous media
    V. Mashayekhizadeh, R. Kharrat, M. H. Ghazanfari, and M. Dejam

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 807-816, Published: 29 February 2012 Informa UK Limited
    Abstract Liquid bridges are believed to play an important role in improving the recovery of fractured reservoirs. However, little is known about the stability of liquid bridges in fractured media at the pore scale. In this work, a glass micromodel representing a stack of two blocks was used at different tilt angles to monitor the frequency and stability of liquid bridges formed during free-fall gravity drainage as a function of tilt angle. It was observed that by increasing the tilt angle, the liquid bridge frequency decreased but its stability increased. This resulted in higher ultimate recovery. In addition, it was found that during the first half of the experiments, the number of bridges was higher but their stability was lower than during the second half of the tests. Moreover, no more than one stable liquid bridge was observed at tilt angles above 20°, and the bridge cross-sectional area was gradually decreased as the stability was maintained. A sequence of bridges that were formed and broken one aft...

  • Five-spot injection/production well location design based on fracture geometrical characteristics in heavy oil fractured reservoirs during miscible displacement: An experimental approach
    Milad Saidian, Mohammad Hossein Ghazanfari, Mohsen Masihi, and Riyaz Kharrat

    Chemical Engineering Communications, ISSN: 00986445, eISSN: 15635201, Volume: 199, Pages: 306-320, Published: February 2012 Informa UK Limited
    Mapping fracture characteristics by using seismic acquisition and processing is important not only to identify sweet spots, but also to optimize production, especially for unconventional heavy oil reservoirs. In this experimental work we used five-spot micromodels initially saturated with heavy oil to find the optimum well locations during first-contact miscible displacement. The experiments were performed at a fixed injection rate on fractured micromodels with various patterns. The optimum location for injection/production wells was found in the pattern where fractures make an angle of 45° with the mean flow direction. Moreover, oil recovery was increased with the density, length, level of scattering, and discontinuity of fractures. The analysis of the experimentally measured recovery curve revealed that there are three distinct stages for each displacement. The efficiency of the first stage was found to be dominated by dispersion and diffusion. However, the recovery of the second stage was significantly...

  • A comprehensive eor study of a highly fractured matured field-Case study (SPE 153311)
    74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources, Pages: 4984-4995, Published: 2012

  • Multi-scale analysis of gamma ray and resistivity logs as a new approach for early flow units identification
    Saint Petersburg 2012 - Geosciences: Making the Most of the Earth's Resources, Published: 2012

  • Multiple-zones flow unit modeling of Ilam and Sarvak carbonate formations of Iran through an integrated approach
    M.B. Shahvar and R. Kharrat

    Society of Petroleum Engineers - 36th Nigeria Annual Int. Conf. and Exhibition 2012, NAICE 2012 - Future of Oil and Gas: Right Balance with the Environment and Sustainable Stakeholders' Participation, Pages: 908-919, Published: 2012 Society of Petroleum Engineers

  • Asphaltene deposition study and its effects on permeability reduction - A case study (SPE 153512)
    74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources, Pages: 5097-5108, Published: 2012

  • A comparative study on WAS, SWAS, and solvent-soak scenarios applied to heavy-oil reservoirs using five-spot glass micromodels
    Seyed Amir Farzaneh, Ali Akbar Dehghan, Mohammad H. Ghazanfari, and Riyaz Kharrat

    Journal of Canadian Petroleum Technology, ISSN: 00219487, eISSN: 21564663, Pages: 383-392, Published: September 2012 Society of Petroleum Engineers (SPE)

  • A review on thermal enhanced heavy oil recovery from fractured carbonate reservoirs
    Eshragh Ghoodjani, Riaz Kharrat, Manouchehr Vossoughi, and Seyed Hamed Bolouri

    Society of Petroleum Engineers - SPE Heavy Oil Conference Canada 2012, Pages: 231-238, Published: 2012 Society of Petroleum Engineers

  • Macroscopic recovery mechanisms of in-situ combustion process in heavy oil fractured systems: Effect of fractures geometrical properties and operational parameters
    S. Mobeen Fatemi, Riyaz Kharrat, Shapour Vossoughi, and Cyrus Ghotbi

    Society of Petroleum Engineers - SPE EOR Conference at Oil and Gas West Asia 2012, OGWA - EOR: Building Towards Sustainable Growth, Pages: 593-617, Published: 2012 Society of Petroleum Engineers

  • On the effect of silica nanoparticles on wettability alteration during water flooding to heavy oils-A micromodel study
    74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources, Pages: 3943-3947, Published: 2012

  • A breakthrough in controlling lost circulation in a pay zone by optimizing the particle size distribution of shellfish and limestone chips
    A. Moazzeni, M. Nabaei, and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 290-306, Published: 14 December 2011 Informa UK Limited
    Abstract The most common drilling problem experienced by drilling engineers is lost circulation, which results in great expense to oil companies because of either drilling fluid supply or subsequent drilling problems like pipe sticking. It becomes more challenging when dealing with heavy mud weights as high as 165 pounds per cubic feet (pcf). To resolve this problem, lost circulation materials (LCMs) are added to the drilling fluid in order to diminish mud loss rate to an acceptable level. Different types of LCMs in use in the drilling industry are employed based on the circumstance. The situation becomes worse when drilling in the reservoir section. In such intervals, the added materials should have the capability to be off the formation when the well is put on back flow or they should be soluble in acid in order to prevent reservoir impairment and reduction in productivity. In this study, it is tried to find the optimum size range of limestone and shellfish for use as LCMs in fractured and loose formati...

  • The operational and reservoir parameters influencing the performance of top-down in situ combustion in fractured reservoirs: 2D block-scale simulation of networked fractures
    S. M. Fatemi, R. Kharrat, and S. Vossoughi

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 256-270, Published: 14 December 2011 Informa UK Limited
    Abstract Top-down in situ combustion (ISC) involves the stable propagation of a combustion front from the top vertical injector to the bottom horizontal producer. With the exception of laboratory studies of conventional sandstones, no application of the process in fractured carbonates has been addressed. The aim of the present work is to study ISC in the presence of a system of networked fractures using a thermal reservoir simulator from the Computer Modeling Group (CMG; Calgary, AB, Canada). The performance of ISC is compared with nonfractured system under similar conditions. To obtain more realistic results, a history-matched and validated combustion model of an Iranian naturally fractured low-permeability carbonate heavy oil reservoir, Kuh-E Mond, was used, and the performance of ISC in a fractured porous medium model was compared with a conventional (nonfractured) reservoir. Operational and reservoir parameters that may influence the performance of the process in the case of a fractured reservoir, suc...

  • Experimental investigation of constant and concentration-dependent diffusivity of a hydrocarbon solvents-heavy oil system: A comparative study
    E. Nasirahmadi, R. Kharrat, M. H. Ghazanfari, and D. Rashtchian

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 235-245, Published: 6 December 2011 Informa UK Limited
    Abstract This work is concerned with the experimental investigation of mass transfer, which occurs during diffusion of hydrocarbon solvents in heavy oil based on constant and concentration-dependent diffusion coefficient. Here, a series of free fall diffusion experiments have been conducted in sealed test tubes at fixed temperatures. Pentane, hexane, and octane were used as solvents and were placed on heavy oil in tubes. The diffusivity of heavy oil into solvents was monitored by a digital camera. The image analysis technique was applied to extract concentration profiles in diffusion zones of solvents by means of calibration curves. Fick's second law was used to obtain both constant and concentration-dependent diffusion coefficient. The measured diffusion coefficients are in agreement with the data reported in the literature for different heavy oils. The results show that the diffusion coefficient experiences an increasing trend with oil concentration till it reaches its maximum and then tails off to a co...

  • Investigation of top-down in-situ combustion process in complex fractured carbonate models: Effects of fractures' geometrical properties
    Society of Petroleum Engineers - Canadian Unconventional Resources Conference 2011, CURC 2011, Pages: 1822-1842, Published: 2011

  • Experimental studies of cationic surfactant adsorption onto carbonate rocks
    Australian Journal of Basic and Applied Sciences, ISSN: 19918178, Pages: 808-813, Published: December 2011

  • The effect of fractures' geometrical properties on the recovery mechanism of the top-down in situ combustion process
    S. Mobeen Fatemi and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 147-158, Published: 30 November 2011 Informa UK Limited
    Abstract The top-down in situ combustion (ISC) involves the stable propagation of the combustion front from the top vertical injector to the bottom horizontal producer. Apart from laboratory studies in conventional sandstones, no application of the process in fractured carbonates has been addressed yet. The authors modified a successful combustion tube history matched model of an Iranian low-permeable heavy oil reservoir called Kuh-E-Mond to investigate the feasibility of ISC in fractured carbonate reservoirs mimicking block-scale combustion cells. Effects of fractured geometrical properties such as orientation, location, extension, density, spacing, and dispersion were considered. Results confirmed a higher outcome in the case of optimum vertical or horizontal fracture density and spacing. Vertical fractures located at the lateral sides of the cell enhanced the process in terms of ultimate oil recovery and oxygen sweep efficiency. The longer vertical fractures and higher dispersion through the reservoir ...

  • New method of generating approximation profile of highly noisy wireline logs through utilizing wavelet non-parametric regression
    Society of Petroleum Engineers Nigeria Annual International Conference and Exhibition 2011, Pages: 540-547, Published: 2011

  • Improvement of heavy oil recovery in the vapex process using montmorillonite nanoclays
    K. Pourabdollah, A. Zarringhalam Moghaddam, R. Kharrat, and B. Mokhtari

    Oil and Gas Science and Technology, ISSN: 12944475, Pages: 1005-1016, Published: November 2011 EDP Sciences
    In this paper, the nanoclay particles were introduced as mobile adsorbents in oil reservoirs to adsorb the asphaltenes, reduce the viscosity and enhance the dispersion. The objective of this paper is experimental investigation of enhanced heavy oil recovery using in situ nanoparticles for the first time. Moreover, two thermal analysis methods (thermogravimetry and differential thermal analysis) were used to analyze the asphaltene content of residue hydrocarbons in the swept chambers in nano-assisted and conventional VAPEX processes. Experiments were carried out using Iranian heavy oil and propane: the setup consisted of two sand-packed cells; one packed only with glass beads as the oil matrix and the other with glass beads and modified montmorillonite as the nanoclay, while they had similar porosity and permeability. The content of deposited asphaltene in swept matrixes, the propagation pattern of vapor chambers in heavy oil matrixes, and the rates of solvent consumption and oil production were determined. The results elucidated that montmorillonite changed the matrix heterogeneity and led to forming enhanced breakthroughs, to increasing the interfacial surface of vapor/bitumen and to accelerating the oil production. It was found that not only was the rate of vapor injection diminished, but the heavy oil recovery was also markedly enhanced by 30(±4)%.

  • An experimental investigation of fracture physical properties on heavy oil displacement efficiency during solvent flooding
    S. A. Farzaneh, A. A. Dehghan, R. Kharrat, and M. H. Ghazanfari

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1993-2004, Published: 2011 Informa UK Limited
    Abstract This work is concerned with the role of geometrical properties of fractures on oil displacement efficiency during solvent injection to heavy oil. Here, a series of solvent injection processes were conducted on one-quarter five-spot fractured micromodels that were initially saturated with the heavy oil, at a fixed flow rate condition. The oil recovery was measured using image analysis of the continuously provided pictures. The results show that for the range of experiments performed here, the maximum oil recovery happens at a fracture orientation angle of 45 degrees. Also, increasing the number of fractures leads to a higher oil recovery factor by solvent in 45 degrees, while it does not change significantly for the case of a 90-degree inclination. By increasing the fracture spacing, the oil recovery factor decreased. When fractures are distributed along the mean flow direction, oil recovery is higher than the case where the fractures are more dispersed and are not in the mean flow direction. In t...

  • Effect of orientation of strata on macroscopic sweep efficiency of water/polymer flooding in layered porous media
    Hamid Emami Meybodi, Riyaz Kharrat, and Benyamin Yadali Jamaloei

    Journal of Porous Media, ISSN: 1091028X, Pages: 761-776, Published: 2011 Begell House

  • An improvement of thermodynamic micellization model for prediction of asphaltene precipitation during gas injection in heavy crude
    Mohammad Tavakkoli, Mohsen Masihi, Mohammad Hossein Ghazanfari, and Riyaz Kharrat

    Fluid Phase Equilibria, ISSN: 03783812, Volume: 308, Issue: 1-2, Pages: 153-163, Published: 25 September 2011 Elsevier BV
    Thermodynamic micellization model is known as an appropriate approach for prediction of asphaltene precipitation. However, the reliability (i.e. accuracy) of this model for whole range of pressure or injected gas mole percent must be checked. In practice, the accuracy can be improved by using a suitable characterization method. In this research, a computer code for implementing the thermodynamic micellization model has been developed. Having used this program, we make the prediction of asphaltene precipitation by using data reported in the literature as well as the experimental data obtained from high pressure, high temperature asphaltene precipitation experiments under gas injection conditions. An enhancement to the thermodynamic micellization model has been proposed by applying the characterization method taken from the thermodynamic solid model. This new approach introduces a new matching parameter representing the interaction coefficients between the asphaltene component and light hydrocarbon components. Sensitivity analysis has emphasized that the thermodynamic micellization model is highly sensitive to this new matching parameter, the resin interaction energy parameter (ΔUr), the interfacial tension between the asphaltene micellar core and the crude (σ0), and the concentration of asphaltene monomers in the crude which is in equilibrium with the pure solid asphaltene phase (Xa1ons). Finally, the predictions obtained from this approach under gas/solvent injection conditions, resulted in a good agreement with experimental data which shows a significant improvement in comparison to the other matches in the available literature.

  • Experimental studying of pore morphology and wettability effects on microscopic and macroscopic displacement efficiency of polymer flooding
    Hamid Emami Meybodi, Riyaz Kharrat, and Majid Nasehi Araghi

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Pages: 347-363, Published: August 2011 Elsevier BV
    Abstract Pore morphology and wettability of a porous medium have dominating effects on microscopic displacement efficiency, and consequently on the ultimate oil recovery. To provide a better understanding of the effects of these parameters on microscopic displacement mechanisms and macroscopic performance of a polymer flood process, a comprehensive experimental study was conducted using five two-dimensional glass micromodels. A combination of three wettability conditions and five different pore structures was used in this study. The selected scenarios include four homogeneous synthetic pore networks at water-, mixed- and oil-wet conditions. A random network that represents the pore space in Berea sandstone was also used for further investigation. Image processing technique was applied to analyze and compare displacement mechanisms and displacement process efficiency in each experiment. Microscopic mechanisms, such as oil and polymer solution trapping, configuration of wetting and non-wetting phases, flow of continuous and discontinuous strings of polymer solution, polymer solution snap-off, distorted flow of polymer solution, emulsion formation, and microscopic pore-to-pore sweep of oil phase were observed and monitored in conducted experiments. Experimental results showed that water- and mixed-wet media generally have comparable and higher recoveries in contrast with oil-wet media. Moreover, the results confirmed a significant dependency on the pore structure and wettability of the media on both displacement mechanisms as well as oil recoveries. This experimental study illustrates the successful application of glass micromodel techniques for studying enhanced oil recovery (EOR) processes in a five-spot pattern, and also provides a useful reference for understanding the displacement mechanisms involved in a polymer flood process at different pore morphologies and wettabilities of porous media.

  • A mechanistic analysis of viscous fingering in low-tension polymer flooding in heavy-oil reservoirs
    Benyamin Yadali Jamaloei, Riyaz Kharrat, and Farshid Torabi

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Pages: 228-232, Published: August 2011 Elsevier BV
    Abstract Modeling of the low tension polymer flooding (LTPF) in heavy oil reservoirs suffers from the paucity of detailed knowledge of viscous instability or fingering effects. Major limitations of previous approaches for studying viscous fingering in immiscible displacements are that the reported experiments have been conducted utilizing the linear displacements schemes in the media with high, single-phase permeabilities. Consequently, viscous instability has not been studied in low-permeability media and using the displacement schemes similar to the oil-field patterns (e.g., five-spot). To help understand viscous fingering in LTPF in heavy oil reservoirs and to overcome the limitations of previous studies, we conducted experiments in the low-permeability, one-quarter, five-spot patterns. New insights into the main driving mechanisms for viscous fingering are proposed. In summary, the mechanisms of spreading, splitting, coalescence, and microscopic crossflow drive the finger growth. In addition, the viscous fingers are readily initiated in the porous medium, but they can be damped out before traveling very far. This damping of the viscous fingers is due to the flow of the two phases in a direction transverse to the direction of bulk fluid movement as a result of dispersive processes such as stream splitting. Also, the initially-developed fingers may deteriorate over the time of displacement. This depends on the distance between the injector and producer and width of the porous medium. The presence of instabilities that look like fingers and stable displacements behind the unstable front were discovered. The results also indicate that a stable zone exists and progresses at varying velocities. Finally, we reveal three different types of displacements that occur in LTPF: stable displacements, displacement with macroscopic viscous fingering, and displacements with both macroscopic and microscopic viscous fingering.

  • Study of Microscopic and Macroscopic Displacement Behaviors of Polymer Solution in Water-Wet and Oil-Wet Media
    Hamid Emami Meybodi, Riyaz Kharrat, and Xiaoqi Wang

    Transport in Porous Media, ISSN: 01693913, Pages: 97-120, Published: August 2011 Springer Science and Business Media LLC
    Performance of a polymer flood process requires the knowledge of rheological behavior of the polymer solution and reservoir properties such as rock wettability. To provide a better understanding of effects of polymer chemistry and wettability on the performance of a polymer flood process, a comprehensive experimental study was conducted using a two-dimensional glass micromodel. A series of water and polymer flood processes were carried out at different polymer molecular weights, degrees of polymer hydrolysis, and polymer concentrations in both water-wet and oil-wet systems. Image processing technique was applied to analyze and compare microscopic and macroscopic displacement behaviors of polymer solution in each experiment. From micro-scale observations, the configuration of connate water film, polymer solution trapping, flow of continuous and discontinuous strings of polymer solution, piston-type displacement of oil, snap-off of polymer solution, distorted flow of polymer solution, emulsion formation, and microscopic pore-to-pore sweep of oil phase were observed and analyzed in the strongly oil-wet and water-wet media. Rheological experiments showed that a higher polymer molecular weight, degree of hydrolysis, and concentration result in a higher apparent viscosity for polymer solution and lower oil–polymer viscosity ratio. It is also shown that these parameters have different impacts on the oil recovery in different wettabilities. Moreover, a water-wet medium generally had higher recovery in contrast with an oil-wet medium. This experimental study illustrates the successful application of glass micromodel techniques for studying enhanced oil recovery (EOR) processes in five-spot pattern and provides a useful reference for understanding the displacement behaviors in a typical polymer flood process.

  • Monitoring of asphaltene precipitation: Experimental and modeling study
    Hassan Nakhli, Ahmad Alizadeh, Mohsen Sadeqi Moqadam, Sajjad Afshari, Riyaz Kharrat, and M.H. Ghazanfari

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Pages: 384-395, Published: August 2011 Elsevier BV
    Abstract Preparing relatively complete collections of experimental data on asphaltene precipitation in different reservoir conditions leads to considerable improvement in this area of science. In this work, asphaltene precipitation was studied upon two Iranian live oil samples, one a heavy oil and another light oil, under primary depletion as well as gas injections. Pressure depletion experiments were carried out at different temperatures to observe temperature effect besides pressure changes on asphaltene phase behavior. CO2, dry and enriched gases were used as injecting agents to investigate the effect of different gases on asphaltene precipitation. Surprisingly, it was observed that raising temperature decreases the amount of precipitation in case of heavy oil while acting in favor of precipitation for light oil sample. In addition, Enriched gas resulted in more precipitation compared to dry one while CO2 acted as hindering agent for light oil samples but increased the amount of precipitation in case of heavy oil. In the next part of this work, polydisperse thermodynamic model was developed by introducing an asphaltene molecular weight distribution function based on fractal aggregation. Modification that was introduced into polydisperse model not only solved the instability problem of Kawanaka model but also eliminates the need for resin concentration calculation. Flory–Huggins and Modified Flory–Huggins thermodynamic solubility models were applied to compare their predictions with proposed model.

  • Asphaltene precipitation prediction using a micellization model based on experimental data
    S. Mahdavi and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1133-1146, Published: 2011 Informa UK Limited
    Abstract Thermodynamic modeling is a promising tool for prediction of asphaltene precipitation. However, most thermodynamic models do not consider the micellar nature of petroleum fluids and the interaction between asphaltene-resin molecules. In addition, the accuracy of the predictions from the Peng-Robinson equation of state (PR-EOS) depends on the mixing rule. In this work, a thermodynamic framework based on the micellization model is used to describe the structure of asphaltene micelles as well as asphaltene precipitation in crude oil and the Wong and Sandler (1992) mixing rule also is applied. The results show that the model predictions are matched well with the generated data for two Iranian crude oils.

  • Quantifying the role of pore geometry and medium heterogeneity on heavy oil recovery during solvent/Co-solvent flooding inwater-wet systems
    Ali Akbar Dehghan, Riyaz Kharrat, Mohammad Hossein Ghazanfari, and S. Vossoughi

    Journal of Porous Media, ISSN: 1091028X, Pages: 363-373, Published: 2011 Begell House

  • The influence of pore geometry on flow instability and pore-scale displacement mechanisms of dilute surfactant flooding in mixed-wet porous media
    Benyamin Yadali Jamaloei and Riyaz Kharrat

    Journal of Porous Media, ISSN: 1091028X, Pages: 91-105, Published: 2011 Begell House

  • Experimental investigation of the asphaltene deposition process during different production schemes
    M.B. Bagheri, R. Kharrat, and C. Ghotby

    Oil and Gas Science and Technology, ISSN: 12944475, Pages: 507-519, Published: May 2011 EDP Sciences
    Experimental Investigation of the Asphaltene Deposition Process during Different Production Schemes — This paper presents the results of asphaltene precipitation and deposition during lean gas injection, CO2 injection and natural depletion in reservoir conditions. In addition, the effect of variations in operating pressure, injection gas concentration and production rate on asphaltene precipitation and deposition were investigated. The severity of asphaltene deposition was found to be more pronounced in lean gas injection in comparison with CO 2 injection and natural depletion. Increasing the flow rate in natural depletion experiments showed a considerable increase in asphaltene deposition, and consequently permeability reduction in the core matrix. Moreover, more asphaltene deposition was observed along the porous media in the gas injection experiments when the gas mol percent of the mixture was increased.

  • The influence of pore wettability on the microstructure of residual oil in surfactant-enhanced water flooding in heavy oil reservoirs: Implications for pore-scale flow characterization
    Benyamin Yadali Jamaloei, Riyaz Kharrat, Koorosh Asghari, and Farshid Torabi

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Pages: 121-134, Published: April 2011 Elsevier BV
    Among many variables that affect the performance of surfactant-based chemical flooding processes, the reservoir pore wettability is considered as the foremost parameter after the reservoir geology. Although considerable attention has been paid to the obviously important subject of wettability effect in these processes, the effect of pore wettability on experimentally determined, quantitative information on blob microstructure and the statistics of blob populations are missing from the literature. The latter is important since changes in size distribution and shapes of blob provide insight into the mechanisms of trapping and mobilization of trapped, residual oil, and relative change in the magnitude of the viscous, capillary, and inertial forces at the pore level. In this study, the changes that occur with change in wettability, from water-wet to oil-wet, in the detailed microstructure of trapped, residual, high-viscosity oil in porous media have been evaluated. To obtain such invaluable information, satisfactory techniques for microscopically capturing statistically representative blob samples and measuring their size distribution have been devised. Once obtained, the experimentally determined oil blob size distribution and the detailed statistics of blob populations have been used to characterize the pore-scale flow behavior of surfactant-enhanced water flooding in the water-wet and oil-wet networks. This pore-scale flow behavior characterization includes the influence of wettability on construction of the relationships between the pore-scale mobilization capillary number and a quantity (which depends on pore geometric properties and the equilibrium radii of curvature of the meniscus of the blob) and the statistical distribution of the mean pore-scale Weber number. Furthermore, mean, median, and maximum pore-scale capillary number values have been determined in the water-wet and oil-wet media. This type of pore-scale flow characterization helps to gain proper knowledge of the change in the magnitude of the viscous, capillary, and inertial forces at the pore level using the statistics of oil blob length and diameter. Finally, the changes in size distribution and shapes of oil blob are linked to some of the pore-level events of oil trapping and mobilization, which are reviewed in this study. The gained knowledge helps modeling recovery of residual oil blobs under different wettability conditions.

  • Pore-Scale Monitoring of Wettability Alteration by Silica Nanoparticles During Polymer Flooding to Heavy Oil in a Five-Spot Glass Micromodel
    Ali Maghzi, Ali Mohebbi, Riyaz Kharrat, and Mohammad Hossein Ghazanfari

    Transport in Porous Media, ISSN: 01693913, Pages: 653-664, Published: April 2011 Springer Science and Business Media LLC
    It is well known that the oil recovery is affected by wettability of porous medium; however, the role of nanoparticles on wettability alteration of medium surfaces has remained a topic of debate in the literature. Furthermore, there is a little information of the way dispersed silica nanoparticles affect the oil recovery efficiency during polymer flooding, especially, when heavy oil is used. In this study, a series of injection experiments were performed in a five-spot glass micromodel after saturation with the heavy oil. Polyacrylamide solution and dispersed silica nanoparticles in polyacrylamide (DSNP) solution were used as injected fluids. The oil recovery as well as fluid distribution in the pores and throats was measured with analysis of continuously provided pictures during the experiments. Sessile drop method was used for measuring the contact angles of the glass surface at different states of wettability after coating by heavy oil, distilled water, dispersed silica nanoparticles in water (DSNW), polyacrylamide solution, and DSNP solution. The results showed that the silica nanoparticles caused enhanced oil recovery during polymer flooding by a factor of 10%. The distribution of DSNP solution during flooding tests in pores and throats showed strong water-wetting of the medium after flooding with this solution. The results of sessile drop experiments showed that coating with heavy oil, could make an oil-wet surface. Coating with distilled water and polymer solution could partially alter the wettability of surface to water-wet and coating with DSNW and DSNP could make a strongly water-wet surface.

  • Pore-Level Observation of Free Gravity Drainage of Oil in Fractured Porous Media
    Vahid Mashayekhizadeh, Mohammad Hossein Ghazanfari, Riyaz Kharrat, and Morteza Dejam

    Transport in Porous Media, ISSN: 01693913, Pages: 561-584, Published: March 2011 Springer Science and Business Media LLC
    This work presents results from two sets of experiments conducted to study, in pore level, the role of fracture aperture and tilt angle on the stability of liquid bridges and the shape of a front during free gravity drainage process. Glass micromodels of two different aperture sizes were used to monitor the mechanism of gravity drainage of air–crude oil system, rotating around a bottom corner to create different tilting angles. Oil content within the matrix blocks was determined as a function of time using a series of images obtained during the experiments, from which net drainage rate from the upper and lower matrix blocks is calculated. Liquid bridges are more frequent but less stable at early time of drainage. The liquid bridges, which have widths as thin as 50 μm, can resist instability to maintain continuity. Liquid bridges formed in stacks with higher tilt angles are more stable, enhancing oil drainage from the upper matrix block and causing higher recoveries. Quantitative analysis of the results shows that a wider fracture aperture increases the oil production rate, but reduces the ultimate recovery. Furthermore, stacks with higher tilt angles present larger ultimate recoveries and smaller production rates. The front geometry in the lower block deviates from linearity due to formation of liquid bridges in the middle fracture. The results of this work can be helpful to better understand the interaction between fractures and matrix blocks.

  • Assessment of Vapor Extraction (VAPEX) process performance in naturally fractured reservoirs
    S. Mobeen Fatemi and Riyaz Kharrat

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Issue: 3-4, Pages: 260-273, Published: January 2011 Elsevier BV
    Abstract The Vapour Assisted Petroleum Extraction (VAPEX) process, a newly developed Enhanced Heavy Oil Recovery process, is a promising EOR method for certain conventional non-fractured heavy oil sandstone reservoirs such as those in Canada, but its applicability on low permeable Naturally Fractured Reservoirs (NFR) such as those in the Middle East and Persian Gulf still remained as a question. Previous studies show that the foremost concern for VAPEX application in the case of NFR is the low non-economical production rates. The aim of the present work is to study the effect of fractures geometrical properties such as orientation (vertical or horizontal), density, spacing, location and networking on the performance of the VAPEX process in low permeable naturally fractured laboratory scale models. To approach the problem, a simulation model was developed and validated according to the previously published VAPEX conventional and fractured experiments. Further, this validated model has been modified to include the inhabitant countercurrent drainage mechanism of VAPEX which has not been considered in the previously published fractured models of VAPEX. Simulation analysis showed that contrary to the horizontal fractures, VAPEX process recovery enhanced in the presence of vertical fractures as compared to the case of conventional model. Fracture spacing was an important parameter on the performance of VAPEX since higher production rates achieved in the case of higher density of vertical fractures. Contrary to this, oil recovery decreased in the case of higher density of horizontal fractures inside the model. Vertical fractures improved the recovery performance of the model in the case of networked fractures as compared to the case of horizontal fractures model. Finally the effects of operational parameters such as vertical offset between two stacked wells and also the application of staggered wells configuration in the case of networked fractures have been investigated. Simulation results confirmed the importance of these parameters to enhance the recovery performance of VAPEX in the presence of fracture network.

  • Simulation and analysis of production induced reservoir compaction using geomechanical formulation of fracturing technology (GFFT) for stress prediction
    Amir Hossein Haghi, Riaz Kharrat, and M.R. Asef

    International Petroleum Technology Conference 2011, IPTC 2011, Published: 2011 International Petroleum Technology Conference

  • Investigation of Steam Assisted Gravity Drainage (SAGD) and Expanding Solvent-SAGD (ES-SAGD) processes in complex fractured models: Effects of fractures' geometrical properties
    Society of Petroleum Engineers - SPE International Heavy Oil Conference and Exhibition 2011, Pages: 170-188, Published: 2011

  • Intelligent prediction of porosity and permeability from well logs for an iranian fractured carbonate reservoir
    J. Naseryan Moghadam, K. Salahshoor, and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 2095-2112, Published: January 2011 Informa UK Limited
    Abstract One of the most important processes in reservoir engineering is reservoir characterization, in which the reservoir parameters such as porosity and permeability are calculated. These parameters have crucial importance in reservoir engineering computations like reserve estimates and reservoir management. Estimation of porosity and permeability from conventional well logs for uncored well intervals is a good suggestion, but the complexity of the fractured carbonate reservoir makes the application of traditional statistical models totally unreliable. In this article the power of the pattern recognition of artificial neural networks (ANNs) has been applied to develop a transformation map from available most related well logs to rock petrophysical properties of Darquvain reservoir in the southwest of Iran. Comparison of the obtained results illustrates that ANN models can yield more reliable results with respect to traditional models of estimating petrophysical properties. An ANN can be utilized as a f...

  • Toe-to-heel air injection: Investigation of the effect of fractures geometrical properties on process performance
    S. M. Fatemi, R. Kharrat, and C. Ghotbi

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 2067-2077, Published: January 2011 Informa UK Limited
    Abstract Toe to heel air injection has been studied on non-fractured sandstone models and is found to be a promising enhanced oil recovery method for certain heavy oil reservoirs, such as those in Canada, but its applicability on fractured reservoirs, such as those in the Middle East, is not investigated yet. The objective of this article is to evaluate the effect of fractures geometrical parameters, such as fracture density, orientation, and location, on the performance of the process in laboratory scale. Simulation results showed that toe-to-heel air injection is more applicable on highly networked fractured reservoirs, such as those that occur in Persian Gulf coast compared to lower density fractured reservoirs.

  • Investigation of the effect of geometrical properties of networked fractures on the efficiency of steam-assisted gravity drainage process
    S. M. Fatemi, R. Kharrat, and S. Vossoughi

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1625-1636, Published: January 2011 Informa UK Limited
    Abstract Various fracture geometrical properties such as orientation, extension, discontinuity, dispersion, location, and networking were investigated. Results indicate improved oil recovery and sweep efficiency in the presence of vertical fractures. Longer vertical fractures seemed to have even more beneficial effects. Horizontal fractures revealed detrimental effects on oil recovery and the performance became worse for longer horizontal fractures. Discontinuous horizontal fractures caused a better performance especially when combined with continuous vertical fractures (networking). Vertical fractures helped the growth of the steam chamber in the vertical direction, which resulted in higher oil recovery. However, horizontal fractures seemed to inhibit growth of the steam chamber in the vertical direction, hence retarding oil recovery.

  • Implementing a novel method for injection efficiency optimization in water flooding process: Case study
    Mashaallah Bostan, Riyaz Kharrat, and Davood Ghorbani

    SPE Production and Operations Symposium, Proceedings, Pages: 579-586, Published: 2011 Society of Petroleum Engineers

  • Modeling of compositional grading and plus fraction properties changes with depth in petroleum reservoirs
    M. H. Nikpoor, R. Kharrat, and Z. Chen

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 914-923, Published: January 2011 Informa UK Limited
    Abstract In this work we use a nonisothermal model to predict compositional variation in a petroleum fluid column; at the same time, a nonisothermal model will be used to predict change of plus fraction molecular weight (and as a result all other its properties) with depth. We will investigate the effect of several factors as mode of characterization, binary interaction coefficients, volume shifts, and near-criticality on the change of physical properties, including bubble point pressure, solution gas–oil ratio, and oil formation volume factor. A computer program will be used to predict the location of the gas–oil contact and we will show how neglecting compositional grading (CG) can lead to serious errors in the calculated initial oil in place.

  • Introducing a new method for predicting PVT properties of Iranian crude oils by applying artificial neural networks
    J. Naseryan Moghadam, K. Salahshoor, and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1066-1079, Published: January 2011 Informa UK Limited
    Abstract In this study artificial neural networks (ANNs) have been applied for the prediction of main pressure, volume, and temperature (PVT) properties, bubble point pressure (Pb), and bubble point oil formation volume factor (Bob) of crude oil samples from different wells of Iranian oil reservoirs. Via a detailed comparison, the great power of ANNs with respect to traditional methods of predicting PVT properties, like Standing, Vasquez and Beggs, and Al-Marhoun, with higher prediction precision up to R2 = 0.990 has been illustrated and the obtained parameters of ANNs for the application of prediction of other crude oil samples has been presented. The applied PVT data set in this study consists of 218 crude oil samples from Iranian reservoirs and for assurance of the applicability of the ANN model the PVT data set has been divided into 2 training (190 samples) and cross validation (28 samples) data sets and obtained ANNs from applying the training data set has been tested on the cross validation data set...

  • The assessment of fracture geometrical properties on the performance of conventional in situ combustion
    S. M. Fatemi, R. Kharrat, and C. Ghotbi

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 613-625, Published: January 2011 Informa UK Limited
    Abstract The aim of the present work is to evaluate the effect of fractures geometrical properties such as orientation, density, location, and networking on the conventional fire flooding (CFF) process performance through simulation analysis. Combustion parameters of a fractured low-permeable carbonate heavy oil reservoir in Iran called Kuh-E-Mond (KEM); applied for simulation study and simulator has been validated with KEM combustion tube experimental data. The validated model was modified to study CFF in 3D semi-scaled combustion cells. Simulation results confirmed that CFF is more feasible in the case of densely fractured reservoirs such as those in the Middle East.

  • The semi-analytical modeling and simulation of the VAPEX process of "Kuh-e-Mond" heavy oil reservoir
    F. Rasti, M. Masihi, and R. Kharrat

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 535-548, Published: January 2011 Informa UK Limited
    Abstract The vapor extraction process (or VAPEX) uses vaporized solvents injected into a horizontal well to form a vapor chamber within the reservoir. Vapor dissolves in the oil and enhances the oil production by decreasing the oil viscosity in heavy oil reservoirs. To evaluate the process we conduct a simulation study on an Iranian heavy oil reservoir called Kuh-e-Mond. In addition, a semi-analytical investigation of the VAPEX process has been performed. The idea is to perform VAPEX simulation for a laboratory model and find a methodology to compare the results of the simulator with the semi-analytical Butler's model. In particular, a semi-analytical dimensionless correlation for production rate that incorporates all involved physical parameters in the VAPEX process is developed. Also, we performed a sensitivity analysis on the proposed correlation to obtain its adjustable parameters and optimize using available experimental data.

  • Pore-scale flow characterization of low-interfacial tension flow through mixed-wet porous media with different pore geometries
    Benyamin Yadali Jamaloei, Koorosh Asghari, and Riyaz Kharrat

    Experimental Thermal and Fluid Science, ISSN: 08941777, Pages: 253-264, Published: January 2011 Elsevier BV
    The low-interfacial tension flow through porous media occurs in surfactant-based enhanced oil recovery (EOR), soil clean-up, underground removal of the non-aqueous phase liquid and dense non-aqueous phase liquid, etc. In surfactant-based EOR processes, numerous works have been carried out to characterize - either qualitatively or quantitatively - the micro- and macro-scale flow behavior. What has been lacking is to link the statistics of oil blobs population (e.g., distribution of blob length and diameter) to the pore-scale phenomena and macro-scale quantities. In particular, no work has been reported to elucidate the effect of the ratio of pore body to throat diameter (i.e., aspect ratio) on the pore-scale characterization based on the blobs population statistics. The significance of the aspect ratio lies in that it describes the geometry of a porous medium and is one of the foremost morphological features. The aspect ratio is also one of the fundamental factors governing the pore-level events. This study presents the effect of aspect ratio on the statistical distribution of the blob length and equivalent diameter and links the blobs population statistics to the observed pore-level events. The pore-scale variation of the ratio of viscous-to-capillary forces acted on the oil blobs at the threshold ofmore » displacement is utilized to characterize the effect of blob length distribution at different aspect ratios. It also provides some insight into correlating the change in oil recovery efficiency and capillary number, by change in aspect ratio, with the change in blobs population statistics. (author)« less

  • Optimal conditions for immiscible recycle gas injection process: A simulation study for one of the Iranian oil reservoirs
    S. Mohammadi, R. Kharrat, M. Khalili, and M. Mehranfar

    Scientia Iranica, ISSN: 10263098, Pages: 1407-1414, Published: December 2011 Elsevier BV
    Abstract Immiscible gas injection is one of the most common enhanced oil recovery methods used under various reservoir conditions. In this work, the immiscible recycle gas injection, as an EOR scenario for improving recovery efficiency in one of the south-west Iranian oil reservoirs, is simulated by a commercial simulator, ECLIPSE. The reservoir fluid is light oil, with an API of 43. The oil bearing formations are carbonate, and so a dual porosity/dual permeability behavior was chosen for better representation of the fracture system. Different sensitivity analyses with respect to several parameters like the number and location of injection/production wells, production/injection rate, completion interval etc., are performed. It has been observed that in conjunction with the number of wells, 1 injection/2 production well pattern was the most efficient case. Also, the well oil production rate of 200 SM 3 /Day and the well bottom-hole pressure of 75 bar provided higher oil recovery. Completion of injection wells in fracture and production wells in matrix have better oilfield efficiency in comparison to other cases. Finally, we proposed optimum conditions for the immiscible recycle gas injection in this reservoir, which maximizes oil recovery efficiency.

  • Identifying reservoir zones of Iranian formations through integrating wireline logs in time-scale space
    73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011, Pages: 4435-4439, Published: 2011

  • Application of Toe-to-Heel Air Injection (THAI) process in fractured carbonate systems: 3D simulation of the effect of fractures geometrical properties, reservoir and operational parameters
    S. Mobeen Fatemi, Cyrus Ghotbi, Riyaz Kharrat, and Amir Badakhshan

    73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011, Pages: 134-165, Published: 2011 Society of Petroleum Engineers

  • Modified screening criteria of potential asphaltene precipitation in oil reservoirs
    Y. H. Shokrlu, R. Kharrat, M. H. Ghazanfari, and S. Saraji

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1407-1418, Published: January 2011 Informa UK Limited
    Abstract In this article, the De Boer method, the most widely used screening criteria for potential asphalt precipitation, is modified by specifying separate plots for each reservoir. The solubility parameter, which is the most important parameter in this method, is calculated by using the concept of refractive index. Accuracy of the predictions was confirmed by the colloidal instability index, asphaltene–resin ratio, and asphaltene instability trend techniques. Finally, the applicability of this approach was checked using six real cases of Iranian reservoirs. These cases were chosen to include oils with different API gravity, asphaltene content, and extremities (severe to no problem).

  • An experimental investigation of asphaltene precipitation during natural production of heavy and light oil reservoirs: The role of pressure and temperature
    A. Alizadeh, H. Nakhli, R. Kharrat, and M. H. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1054-1065, Published: January 2011 Informa UK Limited
    Abstract Many oil reservoirs encounter asphaltene precipitation as a major problem during natural production. In spite of numerous experimental studies, the effect of temperature on asphaltene precipitation during pressure depletion at reservoir conditions is still obscure in the literature. To study their asphaltene precipitation behavior at different temperatures, two Iranian light and heavy live oil samples were selected. First, different screening criteria were applied to evaluate asphaltene instability of the selected reservoirs using pressure, volume, and temperature data. Then, a high pressure, high temperature filtration (HPHT) setup was designed to investigate the asphaltene precipitation behavior of the crude samples throughout the pressure depletion process. The performed HPHT tests at different temperature levels provided valuable data and illuminated the role of temperature on precipitation. In the final stage, the obtained data were fed into a commercial simulator for modeling and predicting...

  • Prediction of asphaltene precipitation during solvent/CO2 injection conditions: A comparative study on thermodynamic micellization model with a different characterization approach and solid model
    Mohammad Tavakkoli, Mohsen Masihi, Mohammad H. Ghazanfari, and Riyaz Kharrat

    Journal of Canadian Petroleum Technology, ISSN: 00219487, Pages: 65-74, Published: March 2011 Society of Petroleum Engineers (SPE)
    There are different thermodynamic models that have been applied for modelling of asphaltene precipitation caused by various reasons, such as solvent/CO 2 injection and pressure depletion. In this work, two computer codes based on two different asphaltene precipitation thermodynamic models—the first being the thermodynamic micellization model with a different characterization approach and the second being the solid model—have been developed and used for predicting asphaltene precipitation data reported in the literature as well as in the obtained data for Sarvak reservoir crude, which is one of the most potentially problematic Iranian heavy oil reserves under gas injection conditions. For the thermodynamic micellization model, a new approach was obtained by applying the characterization method taken from the thermodynamic solid model for oil component characterization. This new approach introduced a new matching parameter to the model, representing the interaction coefficients between asphaltene components and light hydrocarbon components, which resulted in a significant improvement in the thermodynamic micellization model predictions of asphaltene precipitation data under gas injection conditions. The model parameters obtained from a sensitivity analysis were applied in both thermodynamic models, and the experimental data of asphaltene precipitation were predicted. The asphaltene precipitation predictions from the solid model showed good agreement with the data taken under gas/solvent injection conditions. Especially for the trend of the titration curve after the peak point, reasonable agreements were observed which could rarely be found in the available literature. It has been observed that although the thermodynamic micellization model with a different characterization approach is more complex than the solid model, it is able to predict the trends of asphaltene precipitation curves for gas titration conditions reasonably well. Also, its predictions matched well with more experimental data points in comparison to the solid model predictions.

  • The role of throat orientation on dispersion of solvent in crude oil-saturated porous media
    A. R. Rezaeipour, R. Kharrat, M. H. Ghazanfari, and E. Yasari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 649-663, Published: January 2011 Informa UK Limited
    Abstract In this work a series of hydrocarbon solvent injection experiments was performed on glass micromodels with different throat orientations that were initially saturated with crude oil at several fixed flow rate conditions. The solvent concentration as a function of location and time was measured using image analysis of color intensity of continuously provided pictures during the injection process. The provided concentration calibration curve of solvent in crude oil was used for back-calculating the solvent concentration along the dispersion zone. The longitude and transverse dispersion coefficients were determined by fitting the results of the mathematical model to the experimental data. It was found that the longitude dispersion decreased when the throat orientation angle increased. In contrast, the transverse dispersion increased. In addition, two trends were observed in variation of longitudinal and transversal dispersion versus Pe. For Pe > 50, the longitude and transverse dispersivities were e...

  • The dependency of relative permeability on dominated flow regimes under gas gravity assisted flow
    B. Rostami, R. Kharrat, M. Pooladi-Darvish, and C. Ghotbi

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 101-113, Published: January 2011 Informa UK Limited
    Abstract Gas-oil relative permeability is essential for performance predictions of reservoirs with solutions for gas drive, gas cap expansion, or gas injection. The nature of flow in reservoir is determined by the interplay of relative permeability and viscous, gravity, and capillary forces. Displacement experiments of the gas-oil system are performed on long core scale models by varying the petrophysical properties and flow conditions. Experiments are conducted in situations where capillary, gravity, and viscous forces are comparable. The effect of destabilized front velocity on relative permeability and residual saturation is investigated. The results indicate that the relative permeability varies with the balance between the gravity and viscous forces. The relative permeabilities determined by analytical and numerical approaches indicate that higher displacement velocity leads to a higher gas relative permeability and lower oil relative permeability. The residual oil saturation was increased by increas...

  • Iterative coupled experimental-numerical evaluation of dispersivity in fractured porous media using micromodel system
    73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011, Pages: 2461-2466, Published: 2011

  • Experimental study of asphaltene deposition during different production mechanisms
    T. Pak, R. Kharrat, M. Bagheri, M. Khalili, and V. Hematfar

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1853-1863, Published: January 2011 Informa UK Limited
    Abstract Sudden changes in key parameters such as pressure, temperature, and fluid composition may result in asphaltene precipitation and deposition, consequently reducing permeability and porosity as well as well injectivity and productivity. Sandstone cores of an Iranian reservoir were studied under high pressure and temperature. Asphaltene deposition was studied in recycled gas injection, CO2 injection, and natural depletion experiments. The authors observed that these processes could be ranked for the deposition severity viewpoint in the aforementioned order. Qualitatively investigation of cores indicated nonuniform deposition of precipitated asphaltene along a flooded core and reducing deposition from entering core terminal to the core outlet.

  • Experimental and simulation studies of the effect of vertical permeability barriers on oil recovery efficiency during solvent injection processes
    A. A. Dehghan, S. A. Farzaneh, R. Kharrat, M. H. Ghazanfari, and M. Masihi

    Energy Sources, Part A: Recovery, Utilization and Environmental Effects, ISSN: 15567036, eISSN: 15567230, Pages: 1889-1900, Published: January 2011 Informa UK Limited
    Abstract Almost all of the heavy oil reservoirs contain discontinuous permeability barriers (shales) with different structures. However, the effect of shaly layer geometrical characteristics including: spacing from wells, discontinuity, orientation, shaly layers' spacing and length, and heterogeneous distribution on oil recovery factor in the presence of gravity force are not well understood. In this work, a series of solvent injection experiments were conducted on various vertical one-quarter five-spot glass micromodels, containing barriers, which were initially saturated with a heavy oil sample. The oil recovery was measured by analysis of the pictures provided continuously during the injection processes. The experimental data were used for developing and validating a compositional-numerical model. The results indicated that the ultimate oil recovery in the presence of shales is lower than that in homogeneous models. The gravity force caused the solvent to be propagated better in the media. It was obser...

  • Experimental investigation of gas-heavy oil molecular diffusion coefficient in porous media: Experimental results for CO2 in Iranian Crudes
    Navid Mirjordavi, M. Kazemeini, R. Kharrat, M.H. Ghazanfari, and A. Salehi

    Defect and Diffusion Forum, ISSN: 10120386, eISSN: 16629507, Volume: 312-315, Pages: 1049-1054, Published: 2011 Trans Tech Publications, Ltd.
    Molecular diffusion of gases in crude oils plays a crucial role in several oil recovery processes especially in cold-based production process. However, experimental data concerning CO2 diffusivity in heavy oils due to the tedious nature of diffusivity measurements are relatively rare in the open literature. In this work, a comprehensive experimental investigation of the effective molecular diffusion determination of CO2-heavy oil systems in homogeneous porous media was studied. The so-called pressure decay method was applied to measure the molecular diffusivity of carbon dioxide in heavy oil. Furthermore, effect of various parameters such as initial pressure, temperature and porous media on molecular diffusion coefficient have been analyzed and based upon experimental results, a new mathematical correlation for prediction of CO2-heavy oil molecular diffusion coefficient in presence of porous medium as a function of temperature was proposed.

  • Quantifying the role of ultrasonic wave radiation on kinetics of asphaltene aggregation in a toluene-pentane mixture
    I. Najafi, S. M.R. Mousavi, M. H. Ghazanfari, C. Ghotbi, A. Ramazani, R. Kharrat, and M. Amani

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 966-974, Published: January 2011 Informa UK Limited
    Abstract Recently, ultrasonic wave technology has received much attention as a method for removal of asphaltene deposits from the near wellbore region. However, very little is known about another feature of this technology on the kinetics of asphaltene molecules aggregation. In this work, the kinetics of asphaltene flocculation in several crude oil samples exposed to ultrasonic waves for different time intervals is studied by confocal microscopy. The colloidal structural evolutions of flocks are described by analysis of size distribution of flocculated asphaltene particles. The results show that for the first 90 min of flocculation time, the size of aggregates increases rapidly, and a reaction-limited aggregation model matches well with the experimental data for all samples. But, after 90 min, a reduction in aggregate size of sonicated samples is observed, whereas the aggregate size of nonsonicated oil samples increases in close agreement with the diffusion-limited aggregation model. It has been found tha...

  • A newmodel for permeability reduction rate due to calciumsulfate precipitation in sandstone cores
    Hamzeh Ali Tahmasebi, Mohammad Soltanieh, and Riyaz Kharrat

    Journal of Porous Media, ISSN: 1091028X, Pages: 911-922, Published: 2010 Begell House

  • Analysis and correlations of viscous fingering in low-tension polymer flooding in heavy oil reservoirs
    Benyamin Yadali Jamaloei, Riyaz Kharrat, and Farshid Torabi

    Energy and Fuels, ISSN: 08870624, eISSN: 15205029, Pages: 6384-6392, Published: 16 December 2010 American Chemical Society (ACS)

  • Pore-scale events in drainage process through porous media under high- and low-interfacial tension flow conditions
    Benyamin Yadali Jamaloei, Riyaz Kharrat, and Koorosh Asghari

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Issue: 1-2, Pages: 223-233, Published: December 2010 Elsevier BV
    In spite of the available literature on the evaluation of the drainage under the high- and low-interfacial tension (IFT) flow through porous media, distribution and the detailed topology and structure of the displacing non-wetting and the trapped wetting phases at the pore level, and some of the pore-scale phenomena have not been understood in a comprehensive manner. The aim of this study is to provide insight into the above-mentioned issues in a preferentially oil-wet porous medium partially filled with the heavy oil and connate water, which is flooded with the brine (simulating secondary drainage or high-IFT waterflooding) and with the surfactant solution (simulating tertiary drainage or low-IFT surfactant-enhanced waterflooding). This paper consists of two parts. The first part provides a detailed, comprehensive literature survey of the recent advances in the experimental study and modeling of the drainage process in porous media. In the second part, the authors present their experimental observations of the pore-level events and the displacement front configurations of drainage under the high- and low-IFT flow conditions in a one-quarter five-spot, etched glass micromodel. First, distribution, configuration, and topology of the trapped air in primary drainage (i.e., air displacement by brine or connate water) are depicted. Second, the detailed pore-scale topology, structure, distribution, and configuration of the displaced and displacing phases in primary imbibition (i.e., desaturation of the continuous non-wetting phase, or wetting process, which occurs during the displacement of brine in a preferentially oil-wet porous medium by heavy oil), secondary drainage (i.e., desaturation of the continuous wetting phase under the high-IFT flow condition, which occurs during the high-IFT waterflooding in a preferentially oil-wet porous medium), and tertiary drainage (i.e., mobilization of the discontinuous trapped wetting phase under the low-IFT flow condition, which occurs during the low-IFT surfactant-enhanced waterflooding in a preferentially oil-wet porous medium), are elucidated in detail. Third, the major pore-scale displacement phenomena in tertiary drainage under the low-IFT flow conditions are explained. Furthermore, the advance of the displacement front and the flow pattern configuration in the secondary and tertiary drainage are analyzed. Finally, the displacing non-wetting phase blob size distribution in the tertiary drainage is presented together with the values of the desaturated fraction of different phases at different stages of the displacement.

  • Wettability effects in gas gravity-Assisted flow as related to displacement instability
    Behzad Rostami, Riyaz Kharrat, V. Alipour Tabrizy, M. Khosravi, and C. Ghotbi

    Special Topics and Reviews in Porous Media, ISSN: 21514798, eISSN: 2151562X, Pages: 39-47, Published: 2010 Begell House

  • Experimental investigation of tertiary oil gravity drainage in fractured porous media
    M. Rezaveisi, Behzad Rostami, Riyaz Kharrat, Shahab Ayatollahi, and C. Ghotbi

    Special Topics and Reviews in Porous Media, ISSN: 21514798, eISSN: 2151562X, Pages: 179-191, Published: 2010 Begell House

  • Novel approach to mitigate gas production in a high GOR carbonate reservoir with drilled wells - Case study
    SPE Production and Operations Symposium, Proceedings, Pages: 362-374, Published: 2010

  • Analysis of pore-level phenomena of dilute surfactant flooding in the presence and absence of connate water saturation
    Riyaz Kharrat and Benyamin Yadali Jamaloei

    Journal of Porous Media, ISSN: 1091028X, Pages: 671-690, Published: 2010 Begell House

  • The impact of CO2 injection and pressure changes on asphaltene molecular weight distribution in a heavy crude oil: An experimental study
    M. Sadeqimoqadam, H. Firoozinia, R. Kharrat, and M. H. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1728-1739, Published: 2010 Informa UK Limited
    Abstract This work concerns observing the pressure as well as CO2 mole percentage effects on asphaltene molecular weight distributions at reservoir conditions. A high-pressure, high-temperature asphaltene measurement setup was applied, and the amount of precipitated asphaltene at different pressures as well as CO2 mole percentage in an Iranian heavy crude oil was measured. Moreover, the asphaltene molecular weight distributions during titration of crude oil with different n-alkanes were investigated. The gel permeation chromatography (GPC) apparatus was used for characterization of asphaltene molecular weight under different conditions. It has been observed that some thermodynamic changes such as pressure depletion above the bubble point increase the average molecular weight of asphaltene and cause the asphaltene molecular weight distributions changes from a bimodal curve with two maxima to a single maxima curve. One the other hand, below the bubble point, pressure reduction causes a decrease in the avera...

  • An experimental and numerical investigation of solvent injection to heavy oil in fractured five-spot micromodels
    S. A. Farzaneh, M. H. Ghazanfari, R. Kharrat, and S. Vossoughi

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 1567-1585, Published: October 2010 Informa UK Limited
    Abstract In this work a series of solvent injection experiments was conducted on horizontal glass micromodels at several fixed flow rate conditions. The micromodels were initially saturated with heavy crude oil. The produced oil as a function of injected volume of solvents was measured using image analysis of the continuously provided pictures. In order to investigate the macroscopic behavior of the process in different media, several fractured, with constant width, and nonfractured five-spot micromodels were designed and used. The measured data have also been used for verifying and developing a simulation model that was later used for sensitivity analysis of some parameters that affect oil recovery. The results show that when the fracture spacing increased, the oil recovery decreased. In contrast, as the fracture orientation angle (the angle with the mean flow direction) or solvent viscosity increased, the oil recovery increased. A critical value for the ratio of connate water saturation to the oil volum...

  • Study of asphaltene and metal upgrading in the vapor extraction (VAPEX) process
    Kobra Pourabdollah, Abdolsamad Zarringhalam Moghadam, Riyaz Kharrat, and Bahram Mokhtari

    Energy and Fuels, ISSN: 08870624, eISSN: 15205029, Pages: 4396-4401, Published: 19 August 2010 American Chemical Society (ACS)
    The effect of the vapor dew point and matrix permeability on the movement of deposited streaks in the vapor extraction (VAPEX) process was investigated. Furthermore, the distribution of residual hydrocarbons, asphaltenes, resins, and metal chelate in the VAPEX cell was determined. Finally, the pattern of viscosity distribution in the VAPAX cell was calculated using a Computer Modelling Group (CMG) simulator. The experiments were conducted in sand packed on the Iranian bitumen by propane solvent. Asphaltene, resin, and vanadium chelate were measured in residual hydrocarbon of swept zone via American Society for Testing and Materials (ASTM) D6560 and D1548 test methods. The results demonstrated that in vapor dew point and high permeable matrices, precipitated streaks moved faster than other conditions. Distributions of asphaltene, resin, and vanadium chelate showed a reduction in their facial concentration from the vapor injection port to the oil production port, while the distribution of dissolved vanadium...

  • A new mathematical model for force gravity drainage in fractured porous media
    M. Ganjeh Ghazvini, R. Kharrat, and M. Masihi

    Transport in Porous Media, ISSN: 01693913, Pages: 711-724, Published: July 2010 Springer Science and Business Media LLC
    In force gas/oil gravity drainage process in fractured porous media, gas is flowing in both matrix and fractures leading to produce a finite gas pressure gradient. Consequently, viscous force plays an important role for displacing matrix oil toward fractures in addition to gravity force that is required to be modeled appropriately. A new analytical model for estimation of steady state oil saturation distribution with assumption of fixed gas pressure gradient throughout the matrix is presented. Moreover, based on some results of this analytical model a different numerical formulation is developed to predict the performance of oil production process. Comparison of the results obtained from this numerical model with the results of a conventional simulator demonstrates that the newly developed model can be applied with satisfactory accuracy. Numerical simulations show that the viscous displacement in fractured porous media can reduce the capillary threshold height, and thus it suggests the force gravity drainage as a favorable production mechanism when the matrix length is close to the threshold height.

  • Identification of fluid dynamics in forced gravity drainage using dimensionless groups
    Behzad Rostami, Riyaz Kharrat, Mehran Pooladi-Darvish, and Cyrus Ghotbi

    Transport in Porous Media, ISSN: 01693913, Pages: 725-740, Published: July 2010 Springer Science and Business Media LLC
    A number of forced gravity drainage experiments have been conducted using a wide range of the physical and operational parameters, wherein the type, length, and permeability of the porous medium as well as oil viscosity and injection rate were varied. Results indicate that an increase in the Bond number has a positive effect on oil recovery whereas the capillary number has an opposite effect. These trends were observed over a two-order of magnitude change in the value of the dimensionless groups. Furthermore, it was found that use of each number alone is insufficient to obtain a satisfactory correlation with recovery. A combined dimensionless group is proposed, which combines the effect of all the three forces. Recoveries from all the experiments conducted in this study show a very good correlation with the proposed group. The exponent of the Bond number in the proposed group is larger than the capillary number suggesting a larger importance for the former. We then show that the same group provides a good correlation for recovery from additional experiments conducted in this study (in the presence of connate water) with that of another set of experiments in the literature.

  • Pore-level investigation of heavy oil recovery during water alternating solvent injection process
    A. A. Dehghan, S. A. Farzaneh, R. Kharrat, M. H. Ghazanfari, and D. Rashtchian

    Transport in Porous Media, ISSN: 01693913, Pages: 653-666, Published: July 2010 Springer Science and Business Media LLC
    This study concerns with the microscopic and macroscopic fluid distribution and flow behavior during water alternating solvent (WAS) injection process to heavy oil using micromodel generated from thin section of a real rock which has rarely attended in the available literature. In this study, a one-quarter five-spot glass micromodel was deployed to examine the effect of flow media topology on microscopic displacements as well as macroscopic efficiency of WAS process. The micromodel was initially saturated with the heavy oil, and then the hydrocarbon solvent and water were injected alternately into it. The observations confirmed that WAS injection scheme is an effective method for the recovery of the significant amount of residual oil. Using solvent as the leading batch in WAS scheme can really improve the oil recovery by increasing the amount of microscopic sweep efficiency in flow paths, where the molecular diffusion in solvent–heavy oil system occurs. Presence of connate water in WAS scheme can improve the recovery efficiency especially at higher water saturations. Heterogeneity of the medium caused the water to be distributed better in the medium, but the amount of residual oil in the flow area is going to be increased. Small precipitates of asphaltene particles due to solvent injection and localized entrapment of the oil due to heterogeneity effects, water blockage, and deadend pores were observed mainly in this process. The results of this study reveals the pore scale events in WAS injection process and will be helpful for developing reliable simulation models.

  • Pore-scale two-phase filtration in imbibition process through porous media at high- and low-interfacial tension flow conditions
    Benyamin Yadali Jamaloei, Koorosh Asghari, Riyaz Kharrat, and Farid Ahmadloo

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Issue: 3-4, Pages: 251-269, Published: June 2010 Elsevier BV
    Abstract This study provides new insights into pore-scale two-phase filtration during imbibition process through porous media under the high- and low-interfacial tension (IFT) flow conditions. First, the distribution and configuration of imbibing wetting and non-wetting phases in primary imbibition (free spontaneous imbibition or wetting process) is depicted. Second, the detailed pore-scale topology, structure, distribution, and configuration of different phases together with the pore-scale displacement mechanisms in primary drainage (i.e., desaturation of continuous wetting phase or de-wetting process), secondary imbibition (i.e., controlled spontaneous imbibition or desaturation of continuous non-wetting phase in high-IFT flow condition), and tertiary imbibition (i.e., forced imbibition or mobilization of discontinuous trapped non-wetting phase in low-IFT flow condition), are expounded. Finally, the advance of the displacement front and flow pattern configuration in secondary and tertiary imbibition is demonstrated and discussed. Furthermore, in tertiary imbibition, the blob size distribution of the displacing wetting phase, formation of the secondary displacement front and wetting film before breakthrough of the displacing wetting phase, rate-dependency of the advance of secondary displacement front and wetting film, interruption of the wetting film flow within wetting film region, pore-level phenomena within the wetting film region, and role of wetting film in pore-scale displacement mechanism are elucidated.

  • Prediction of asphaltene precipitation during pressure depletion and CO2 injection for heavy crude
    M. Tavakkoli, R. Kharrat, M. Masihi, and M. H. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 892-902, Published: June 2010 Informa UK Limited
    Abstract In this work, a thermodynamic approach is used for modeling the phase behavior of asphaltene precipitation. The precipitated asphaltene phase is represented by an improved solid model, and the oil and gas phases are modeled with an equation of state. The Peng-Robinson equation of state (PR-EOS) was used to perform flash calculations. Then, the onset point and the amount of precipitated asphaltene were predicted. A computer code based on the solid model was developed and used for predicting asphaltene precipitation data reported in the literature as well as the experimental data obtained from high-pressure, high-temperature asphaltene precipitation experiments performed on Sarvak reservoir crude, one of Iranian heavy oil reserves, under pressure depletion and CO2 injection conditions. The model parameters, obtained from sensitivity analysis, were applied in the thermodynamic model. It has been found that the solid model results describe the experimental data reasonably well under pressure depletio...

  • Dimensionless correlation for the prediction of permeability reduction rate due to calcium sulphate scale deposition in carbonate grain packed column
    Hamzeh Ali Tahmasebi, Riyaz Kharrat, and Mohammad Soltanieh

    Journal of the Taiwan Institute of Chemical Engineers, ISSN: 18761070, Pages: 268-278, Published: May 2010 Elsevier BV
    Abstract In this work, an experimental and theoretical study has been conducted to investigate the permeability reduction due to CaSO4 scale deposition in packed column porous media. Permeability reduction by calcium sulphate deposition follows a systematic trend considering various important parameters that are affected in this complex process. Hence, a novel dimensionless model has been proposed for the prediction of permeability reduction rate with high accuracy. The developed model is based on the data obtained from glass bead and carbonate grain packed column at low pressure. The proposed model was validated with Berea sandstone cores data at high pressure (100–20,678 kPa), various flow rates (5–15 cm3/min), different temperatures (45–95 °C) and various concentrations of calcium and sulphate ions in brine solutions (0.0125–0.0225 mol/L).

  • Gas-oil relative permeability and residual oil saturation as related to displacement instability and dimensionless numbers
    B. Rostami, R. Kharrat, C. Ghotbi, and S.H. Tabatabaie

    Oil and Gas Science and Technology, ISSN: 12944475, Pages: 299-313, Published: March 2010 EDP Sciences
    Displacement experiments of the gas-oil system are performed on long core scale models by varying the petrophysical properties and flowing conditions. Experiments are conducted in situations where capillary, gravity and viscous forces are comparable. From oil production history and picture analysis, the threshold for the stability is determined. The experimental findings are comparable to the results of a gradient percolation theory. The effect of destabilized front velocity on relative permeability and residual saturation is investigated. The relative permeabilities determined by using analytical and numerical approaches indicate that higher displacement velocity leads to a higher gas relative permeability and lower oil relative permeability. The remaining oil saturation is found to be much higher for displacement velocity above the stabilized criterion. Displacement morphology including the average remaining oil saturation is then described using dimensionless groups expressed as Bond and capillary number. Experimentally determined remaining oil saturation shows a direct and inverse relation to the capillary and Bond number respectively. Hence, a combined dimensionless group has been proposed to generalize the estimation of remaining and residual oil saturations under the range of dimensionless numbers studied here.

  • Analysis of microscopic displacement mechanisms of dilute surfactant flooding in oil-wet and water-wet porous media
    Benyamin Yadali Jamaloei and Riyaz Kharrat

    Transport in Porous Media, ISSN: 01693913, Pages: 1-19, Published: January 2010 Springer Science and Business Media LLC
    In all the enhanced oil recovery processes, flow of displacing and displaced fluids on a microscopic scale in a petroleum reservoir rock is affected by the wettability of the reservoir rock. Gaining proper knowledge of the dominant microscale multiphase flow mechanisms enables us to better predict the foremost prevailing macroscale flow behavior of the process. This research provides new insights into the effect of wettability on microscopic two-phase flow displacement mechanisms of dilute surfactant flooding using micromodel. It was inferred that the primary mechanisms of dilute surfactant flooding in the oil-wet medium were, intra-pore and inter-pore bridging of the surfactant solution, pore wall transportation of the oleic phase, formation of water-in-oil macroemulsion, and formation of partially continuous surfactant solution which enhanced the oil recovery. In water-wet medium, transportation of oil phase along pore body and neck walls, complete and incomplete inter-pore bridging, and deformation and stringing of the residual oil were the primary mechanisms of dilute surfactant flooding which made the residual oil entrapped in micromodel easily move forward and enhance oil recovery.

  • A mechanistic analysis of viscous fingering in low-tension polymer flooding in heavy-oil reservoirs
    SPE Latin American and Caribbean Petroleum Engineering Conference Proceedings, Pages: 277-282, Published: 2010

  • Analysis and correlations of viscous fingering in low-tension polymer flooding in heavy oil reservoirs
    Benyamin Yadali Jamaloei, Riyaz Kharrat, and Farshid Torabi

    Society of Petroleum Engineers - Canadian Unconventional Resources and International Petroleum Conference 2010, Pages: 1326-1337, Published: 2010 Society of Petroleum Engineers

  • Asphaltene precipitation study during natural depletion at reservoir conditions
    Sajjad Afshari, Riyaz Kharrat, and Mohammad Hossein Ghazanfari

    Society of Petroleum Engineers - International Oil and Gas Conference and Exhibition in China 2010, IOGCEC, Pages: 179-186, Published: 2010 Society of Petroleum Engineers

  • Applying flow zone index approach and artificial neural networks modeling technique for characterizing a heterogeneous carbonate reservoir using dynamic data: Case Study of an Iranian reservoir
    Mohammad Bagher Shahvar, Riyaz Kharrat, and Mahdi Matin

    Society of Petroleum Engineers - Trinidad and Tobago Energy Resources Conference 2010, SPE TT 2010, Pages: 677-690, Published: 2010 Society of Petroleum Engineers

  • Visualization and quantification of asphaltinic-heavy oil displacement by co-solvents at different wettability conditions
    A. A. Dehghan, R. Kharrat, and M. H. Ghazanfari

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 176-189, Published: January 2010 Informa UK Limited
    Abstract Despite numerous experimental studies, there is a lack of fundamental understanding on how the chemical composition of a co-solvent at different wettability conditions might affect the pore-scale events and oil recovery efficiency in 5-spot models. In this study visualization of solvent injection experiments performed on a one-quarter five spot glass micromodel, which was initially saturated with the crude oil. One hydrocarbon solvent was considered as base, and four other groups of commercial chemicals, as well as their mixtures, were used as co-solvents. Microscopic and macroscopic displacement efficiency of solvent mixtures in both strongly water-wet and oil-wet media has been studied. It has been observed that small aggregates of asphaltene can improve oil recovery to some extent during early stages of solvent injection. Different groups of chemicals showed various effects on oil recovery based on their nature. An optimum mixture with some percent of commercials containing alcohol group with ...

  • Experimental study of solvent flooding to heavy oil in fractured five-spot micro-models: The role of fracture geometrical characteristics
    S.A. Farzaneh, R. Kharrat, and M.H. Ghazanfari

    Journal of Canadian Petroleum Technology, ISSN: 00219487, Pages: 36-43, Published: March 2010 Society of Petroleum Engineers (SPE)
    The solvent-based process appears to be an increasingly feasible technology for the extraction of heavy oil reserves. However, there is a lack of fundamental understanding of how fracture geometrical characteristics control the oil recovery efficiency in this type of enhanced oil recovery (EOR) technique. In this work, a series of experiments were performed whereby the pure and mixed hydrocarbon solvents (HCS) displaced heavy oil in fractured five-spot glass micro-models. Successive images of the solvent injection process were recorded. The oil recovery factor, as a function of injected pore volume of solvents, was measured using image analysis of the provided pictures. It has been observed that the oil recovery decreased when the fractures' spacing, discontinuity, overlap, and distribution increased. In contrast, the oil recovery increased when the orientation angle, discontinuity-distribution and the number of fractures increased. Also, it has been found that there is an optimum solvent composition, which maximizes the oil recovery. Finally, some pore-level visualization representing the role of asphaltene precipitation during miscible injection was illustrated using these experiments. This study demonstrates the applicability of the micro-models for the fundamental studying of the solvent-based process in fractured five-spot systems, which are used to investigate the effect of fracture geometrical characteristics and their effect on oil recovery.

  • Modeling fluid flow under sonic wave field in fractured porus media-with an approach to capillary forces
    I. Najafi, M. Ghazanfari, C. Ghotbi, and R. Kharrat

    4th International Conference and Exhibition: New Discoveries through Integration of Geosciences, Saint Petersburg 2010, Published: 2010 EAGE Publications BV
    Till now, no mathematical model is presented to model the flow under sonic field be applied in fractured reservoirs. This will be more noticeable when we bear in mind that several reservoirs in Middle East region are fractured. In this work the effects of elastic waves on capillary trapping and mobility of Bingham plastic fluids in fractures have been investigated. Eventually, a model for predicting the influence range of the wave in fractured reservoirs is presented. The results of this study clarified that radiation of wave with low frequency and intensity extremely increases the flow rate and decreases the minimum pressure gradient required for flow of Bingham plastic fluids in fractured porous media. In addition, the fractional flow of Bingham plastic fluid is increased dramatically. Further, it is shown that the effect of elastic wave is of less importance in higher pressure gradients. Finally, according to this mathematical study, it has been observed that this technology would not be applicable in high pressure fractured reservoirs.

  • Modeling and optimization of asphaltene deposition in porous media using genetic algorithm technique
    Society of Petroleum Engineers - International Oil and Gas Conference and Exhibition in China 2010, IOGCEC, Pages: 479-491, Published: 2010

  • Dynamic modeling and optimization of asphaltene deposition in reservoir rocks using genetic algorithm
    72nd European Association of Geoscientists and Engineers Conference and Exhibition 2010: A New Spring for Geoscience. Incorporating SPE EUROPEC 2010, Pages: 4291-4295, Published: 2010

  • Statistical model for dispersion in a 2D glass micromodel
    Mohammad Hossein Ghazanfari, Riyaz Kharrat, Dawood Rashtchian, and Shapour Vossoughi

    SPE Journal, ISSN: 1086055X, Pages: 301-312, Published: June 2010 Society of Petroleum Engineers (SPE)

  • Relationship between wetting properties and macroscale hydrodynamics during forced gravity drainage and secondary waterflood
    B. Rostami, R. Kharrat, C. Ghotbi, and V. Alipour Tabrizy

    Petroleum Science and Technology, ISSN: 10916466, eISSN: 15322459, Pages: 804-815, Published: January 2010 Informa UK Limited
    Abstract In order to relate the wetting properties at the pore scale to the macroscale prevailing forces, a series of experiments was performed in vertical porous media under forced gas invasion at various wettability conditions with partially spreading oil. To describe the dynamics of oil recovery in a three-phase flow condition, the downward gas flood experiments were continued by water injection from the bottom. Experimental results obtained in situations where the magnitudes of viscous, capillary, and gravity forces are comparable. We study the transition from flow configurations where the interface is stable with respect to viscous instability to flow configurations where viscous fingering occurs. The results also have been analyzed using a dimensionless number.

  • Quantitative analysis of ultrasonic wave radiation on reversibility and kinetics of asphaltene flocculation
    4th International Conference and Exhibition: New Discoveries through Integration of Geosciences, Saint Petersburg 2010, Published: 2010

  • Bubble point pressure empirical correlation
    Society of Petroleum Engineers - Trinidad and Tobago Energy Resources Conference 2010, SPE TT 2010, Pages: 361-371, Published: 2010

  • Permeability prediction of un-cored intervals using new IMLR method and artificial neural networks: A case study of Bangestan field, Iran
    Mohammad Nazari Naeeni, Hadi Zargari, Rahim Ashena, Rahman Ashena, and Riyaz Kharrat

    Society of Petroleum Engineers - Nigeria Annual International Conference and Exhibition 2010, NAICE, Pages: 882-890, Published: 2010 Society of Petroleum Engineers

  • Modeling the toe-to-heel air injection process by introducing a new method of type-curve match
    Society of Petroleum Engineers Western North American Regional Meeting 2010 - In Collaboration with the Joint Meetings of the Pacific Section AAPG and Cordilleran Section GSA, Pages: 282-295, Published: 2010

  • Modified distributed delay model for void wave dynamics in gas-lifted wells
    E. Jahanshahi, K. Salahshoor, and R. Kharrat

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Issue: 3-4, Pages: 203-213, Published: December 2009 Elsevier BV
    Abstract Oil well instabilities cause production losses. One of these instabilities, referred to as the “density wave” or “void wave”, is an oscillatory phenomenon which occurs in gas-lift oil wells. A modified distributed delay model is presented for this dynamic behavior in this paper. Then, the proposed model is used for stability analysis of a hypothetic gas-lift oil well undergoing this type of instability. Stability analysis is performed via small gain theorem and simulation studies are subsequently carried out using OLGA as a realistic multi-phase flow simulator. It is shown that the resulting model and its corresponding stability margin are more consistent with observations obtained from well operation facts, compared to the results reported from the previous works.

  • Experimental and theoretical investigation of inorganic scale deposition in carbonated micromodels
    Negar Mosavati, Riyaz Kharrat, Seyed Amir Farzaneh, and Mohammad Hossein Ghazanfari

    Proceedings of the 7th International Conference on Nanochannels, Microchannels, and Minichannels 2009, ICNMM2009, Issue: PART B, Pages: 949-956, Published: 2009 ASMEDC
    In this study, a series of experiments have been conducted on glass micromodel to investigate the effect of different parameters on the gradual process of Barium Sulphate precipitation. Due to the visual nature of the glass micromodel, the shape, size and distribution of scaling formation in a carbonate-rock-look-alike pattern with water-wet characteristics is precisely observable. In addition, an exponential functionality (correlation) was proposed which incorporates all physical parameters affecting the behavior of the system in a dimensionless form. Reynolds number and deviation from equilibrium conditions are the backbones of this correlation. The adjustable exponents of the equation were determined by using a suitable optimization algorithm. This meaningful correlation can also predict the core extracted data with reasonable accuracy. The microscopy observation results confirmed that the deposition is initiated and extended in the middle space of pores and throats. In addition, by increasing the temperature and brine concentration as well as by decreasing the flow rate, the size of crystals was grown. Moreover, the experimental results indicated that by increasing the temperature and brine concentration as well as by decreasing the flow rate, the scaling tendency was increased.


  • Experimental and theoretical study of calcium sulphate precipitation in porous media using glass micromodel
    S. M. Ghaderi, R. Kharrat, and H. A. Tahmasebi

    Oil and Gas Science and Technology, ISSN: 12944475, Pages: 489-501, Published: July 2009 EDP Sciences
    Mixing of two incompatible waters in water injection projects is usually associated with mineral scale formation and deposition in porous media. Deposition process dramatically affects the performance of water injection scenarios by reduction of porosity and mainly permeability of the rock. In this study, a series of experiments has been conducted to investigate the effect of different parameters on the gradual process of Calcium Sulphate precipitation. These include temperature, concentration of mixing brines, pressure, and flow rate. Due to the visual nature of the glass micromodel, a glass sandstone pattern with water-wet characteristics was used as porous medium to easily observe the scaling formation and distribution. In addition, tracing the movement of the solid particles is highly facilitated in this newly suggested experimental setup. The captured photos in microscopy scanning show that the deposition is initiated from the walls of the pores and throats and extend toward the middle space of porous medium and solid crystals look like chicken roost. For better understanding of the effect of any aforementioned parameter, the related permeability reduction curve versus injected pore volume of the brine solutions was plotted. The results indicated that as the temperature, brine concentration, and flow rate increase the scaling tendency increases as well. The pressure has a minor role on the process development. Deposition of CaSO 4 manifests a functional form of permeability reduction due to the effect of different parameters. Therefore, an exponential functionality (correlation) was proposed which incorporates all physical parameters that affect the behavior of the system in dimensionless form. Reynolds number, scaling index, and deviation from equilibrium conditions are the backbone of this correlation. The adjustable exponents of the equation was determined and optimized by means of Genetic Algorithm optimization scheme. This meaningful correlation can also predict the core extracted data with reasonable accuracy.

  • Transport Property Estimation of Non-Uniform Porous Media
    Iranian Journal of Chemistry and Chemical Engineering, ISSN: 10219986, Pages: 29-42, Published: June 2009

  • Integration of 3D seismic attributes and well logs for electrofacies mapping and prediction of reliable petrophysical properties
    Society of Petroleum Engineers - EUROPEC/EAGE Conference and Exhibition 2009, Published: 2009

  • Reservoir rock typing in a carbonate reservoir- Cooperation of core and log data: Case study
    Mitra Chekani and Riyaz Kharrat

    Society of Petroleum Engineers - SPE/EAGE Reservoir Characterization and Simulation Conference 2009 - Overcoming Modeling Challenges to Optimize Recovery, Pages: 129-150, Published: 2009 Society of Petroleum Engineers
    Reservoir characterization is one of the most challenging subjects in Carbonate reservoirs. In this study Flow Zone Index, Winland and initial water saturation methods were used to classify rock typing in an Iranian oil field located in the southeastern region. In addition, the predicted initial water saturation along with log and core data was used for capillary pressure estimation. The studied field is a Cretaceous fractured oil bearing reservoir composed of tightly packed limestone characterized by high porosity but poor permeability with a thickness of 55-65 meters throughout the reservoir. The matrix permeabilities and porosity are in the range of 0.01-150 md and 5-40 percent respectively. The oil gravity is 21.5 degree API. Conventional Core data were first used to define the rock types for the cored intervals in which nine district rock types were defined. Furthermore, the FZI (Flow Zone Index) log was also generated based on the permeability which was obtained from FMI (Full-bore Formation Micro Imager) and porosity logs of cored and un-cored intervals. In addition, SLMP (Stratigraphic Modified Lorenz) plots were generated for the purpose of identifying flow zone and barriers in each well. Also, Winland method was also used for the same purpose. The results of SLMP were consistent with Winland result and FZI. The Scanning Electro Microscopy Photomicrographs of the obtained rock type were studied and found to be consistent with the finding of this work. Further, the available initial water saturations obtained from log data were classified in three groups and found to consistent with FZI and Winland methods. Based on the DRT (District Rock Type) obtained from the FZI method a correlation between initial water saturation from the log and DRT was developed for the purpose of initial water saturation prediction. The generated data was used for the capillary pressure and relative permeability estimation. The generated capillary pressure and relative permeability were consistent with available scale data and provided sufficient Pc curve for the uncored intervals.

  • Application of cyclic steam stimulation by horizontal wells in iranian heavy oil reservoirs
    Scientia Iranica, ISSN: 10263098, Issue: 2 C, Pages: 125-139, Published: July-December 2009

  • Fundamental study of pore morphology effect in low tension polymer flooding or polymer-assisted dilute surfactant flooding
    Benyamin Yadali Jamaloei and Riyaz Kharrat

    Transport in Porous Media, ISSN: 01693913, Pages: 199-218, Published: 2009 Springer Science and Business Media LLC
    Low Tension Polymer Flooding or Polymer Assisted Dilute Surfactant Flooding is generally deployed as a method to produce additional oil trapped in oil reservoirs after waterflooding. Fundamental study of microscopic mechanisms and pore-level phenomena in Polymer Assisted Dilute Surfactant Flooding needs more investigation. Of particular concern and interest is to probe into and document the effect of pore morphology and structure on microscopic phenomena occurring at pore level. No previous works on the effect of pore morphology in Polymer Assisted Dilute Surfactant Flooding has been reported in the literature. In this study, one-quarter five-spot glass micromodels were deployed to examine the effect of porous media morphology and structure on microscopic mechanisms as well as macroscopic behavior of Polymer Assisted Dilute Surfactant Flooding. Four types of pore morphologies were employed to study this factor. Results show that the pore geometric properties in a porous medium will dictate the degree of displacement front instability, capillary imbalance, viscous fingering, wetting characteristics and its distribution, and finally magnitude of ultimate oil recovery. We also found that the formation of flow scheme is dramatically influenced by the pre-designed injection scheme.

  • Oil Formation Volume Factor correlation for Middle East crude oils
    B. Moradi, E. Malekzadrh, and R. Kharrat

    1st International Petroleum Conference and Exhibition, Published: 2009 EAGE Publications BV
    Oil Formation Volume Factor (OFVF) is an important reservoir fluid property. Ideally, OFVF is determined experimentally in the laboratory; However, this value is not always available and correlations are consequently used to determine it. At this work, first the published OFVF are reviewed and then a new correlation is developed to estimate OFVF of crude oils in Middle East. This correlation is applicable for crude oils of API ranging between 19 to 49. The comparison of this new correlation with other published ones shows that it is much more accurate then the other ones. The absolute average deviation error (percent) of the new correlation is about 1.13%.


  • Experimental investigation of wettability effect on co-solvent flooding of heavy oil reservoirs
    Tunis 2009 - 4th North African/Mediterranean Petroleum and Geosciences Conference and Exhibition, Published: 2009

  • Incorporating fuzzy logic and artificial neural networks for building a hydraulic unit-based model for permeability prediction of a heterogeneous carbonate reservoir
    Mohammad Bagher Shahvar, Riyaz Kharrat, and Ramin Mahdavi

    Society of Petroleum Engineers - International Petroleum Technology Conference 2009, IPTC 2009, Pages: 2359-2374, Published: 2009 International Petroleum Technology Conference

  • Selection of proper criteria in flow behavior characterization of low tension polymer flooding in heavy oil reservoirs
    Benyamin Yadali Jamaloei, Riyaz Kharrat, and Farid Ahmadloo

    Society of Petroleum Engineers - Kuwait International Petroleum Conference and Exhibition, KIPCE 2009: Meeting Energy Demand for Long Term Economic Growth, Pages: 469-488, Published: 2009 Society of Petroleum Engineers

  • Thermodynamic modelling of asphaltene precipitation for heavy crude: A comparative study of thermodynamic micellization model and solid model
    M. Tavakkoli, M. Masihi, R. Kharrat, and M.H. Ghazanfari

    Canadian International Petroleum Conference 2009, CIPC 2009, Published: 2009 Petroleum Society of Canada

  • Pressure-Volume-Temperature correlations for Iranian Crude oils
    B. Moradi, E. Malekzadeh, R. Kharrat, and P. Moradi

    1st International Petroleum Conference and Exhibition, Published: 2009 EAGE Publications BV
    ABSTRACT Pressure-Volume-Temperature (PVT) properties are necessary to reservoir engineering calculations in porous media and it is important for calculations in pipeline as well. This work presents a new set of correlation for estimating Iranian Crude oils properties based on some experimental data. Whenever, these is no representative experimental PVT data, these correlations can be used for oils of API ranging between 19 to 42. New correlations was developed to calculate Oil Formation Volume Factor (Bo), Bubble point pressure (Pb) and solution Gas oil Ratio (Rs). Finally, a comparison is made between these correlations and other published correlations such as Standing, Vazquez & Beggs, Glaso, Farshad and et al, Al Marhoun, Petrosky & Farshad, Hanafi and et al and it is found out that these new correlation are more accurate then the other ones.

  • A comparative study of WAS, SWAS and solvent-soak scenarios applied to heavy oil reservoirs using 5-spot glass micromodels
    S.A. Farzaneh, A.A. Dehghan, R. Kharrat, and M.H. Ghazanfari

    Canadian International Petroleum Conference 2009, CIPC 2009, Published: 2009 Petroleum Society of Canada

  • Partial movement of asphaltene in presence of connate water in VAPEX process
    Mojtaba Ardali, Riyaz Kharrat, Behzad Rostami, and Mohammad Derakhshanfar

    Society of Petroleum Engineers - EUROPEC/EAGE Conference and Exhibition 2009, Published: 2009 Society of Petroleum Engineers

  • Effect of mixed gas solvent injection on performance of the vapex process in an iranian heavy oil sample
    M. Derakhshanfar, R. Kharrat, B. Rostami, and S.R. Etminan

    Canadian International Petroleum Conference 2009, CIPC 2009, Published: 2009 Petroleum Society of Canada

  • The role of pore geometry and connate water on miscible displacement of heavy oil with hydrocarbon solvents in strongly water-wet and oil-wet media using five-spot micromodels
    A.A. Dehghan, S.A. Farzaneh, R. Kharrat, and M.H. Ghazanfari

    Canadian International Petroleum Conference 2009, CIPC 2009, Published: 2009 Petroleum Society of Canada

  • Investigating the effect of co-solvents on heavy oil recovery in different pore geometries using five-spot micromodels
    15th European Symposium on Improved Oil Recovery 2009, Pages: 669-682, Published: 2009

  • Studying the effects of pore geometry, wettability and co-solvent types on the efficiency of solvent flooding to heavy oil in five-spot models
    Ali Akbar Dehghan, Riyaz Kharrat, Mohammad Hossein Ghazanfari, and Seyed Amir Farzaneh

    Society of Petroleum Engineers - SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition 2009, APOGCE 09, Pages: 642-652, Published: 2009 Society of Petroleum Engineers

  • Prediction of asphaltene precipitation during gas injection in heavy crude using micellization model with a new approach
    71st European Association of Geoscientists and Engineers Conference and Exhibition 2009: Balancing Global Resources. Incorporating SPE EUROPEC 2009, Pages: 1124-1128, Published: 2009

  • Rock type and permeability prediction of a heterogeneous carbonate reservoir using artificial neural networks based on flow zone index approach
    Riyaz Kharrat, Ramin Mahdavi, Mohammad Hashem Bagherpour, and Shahab Hejri

    SPE Middle East Oil and Gas Show and Conference, MEOS, Proceedings, Pages: 667-684, Published: 2009 Society of Petroleum Engineers

  • Simulation Study of permeability impairment due to asphaltene deposition in one of the iranian oil fractured reservoirs
    A. Mirzabozorg, M.B. Bagheri, R. Kharrat, J. Abedi, and C. Ghotbi

    Canadian International Petroleum Conference 2009, CIPC 2009, Published: 2009 Petroleum Society of Canada

  • Effect of pressure and CO2 composition changes on distribution of asphaltene molecular weight in heavy crude oil
    Canadian International Petroleum Conference 2009, CIPC 2009, Published: 2009

  • Experimental investigation of effect of depletion rates on recovery of a heavy oil reservoir
    15th European Symposium on Improved Oil Recovery 2009, Pages: 274-284, Published: 2009

  • A novel method to develop a new scaling equation for modeling of asphaltene precipitation
    Mohammad Bagher Bagheri, Riyaz Kharrat, Arash Mirzabozorg, Cyrus Ghotbi, and Zohrab Dastkhan

    Society of Petroleum Engineers - SPE/EAGE Reservoir Characterization and Simulation Conference 2009 - Overcoming Modeling Challenges to Optimize Recovery, Pages: 831-844, Published: 2009 Society of Petroleum Engineers

  • Studies of Iranian heavy oils pertinent to reservoir conditions for their auto-ignition to initiate fire flooding
    Dennis Price, Samaneh Razzaghi, Riyaz Kharrat, Davood Rashtchian, and Shapour Vossoughi

    Chemical Engineering Communications, ISSN: 00986445, eISSN: 15635201, Volume: 196, Pages: 643-657, Published: 2009 Informa UK Limited
    In this work, the potential for the auto-ignition of Iranian heavy oil during in situ combustion (ISC) process conditions was studied. Kinetic studies were carried out using thermal analysis techniques. Effects of oxygen partial pressure, reservoir pressure, and clay on the auto-ignition condition were investigated. Based on the experimental results obtained, a kinetic equation was derived for each of the different oil samples in the presence of different sands. The effect of partial pressure of oxygen in the injected air showed that at atmospheric pressure, low temperature combustion (LTC) was initiated at 275°C. Also, enriching the injected air by oxygen lowers the initial LTC temperature by up to 50°C. ARC experiments were undertaken to extend the studies to reservoir pressure conditions (1300 psi). It was found that activation energy in the LTC region was lowered as a consequence. As a result, initiation of LTC commenced at 115°C when air was injected. The effect of clay as a catalyst was also studied...

  • Developing a new scaling equation for modelling of asphaltene precipitation
    M.B. Bagheri, A. Mirzabozorg, R. Kharrat, Z. Dastkhan, C. Ghotbi, and J. Abedi

    Canadian International Petroleum Conference 2009, CIPC 2009, Published: 2009 Petroleum Society of Canada

  • Experimental investigation of factors affecting miscible two-phase flow in fractured and non-fractured micromodels
    Seyed Amir Farzaneh, Riyaz Kharrat, and Mohammad Hossein Ghazanfari

    Proceedings of the 6th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM2008, Issue: PART B, Pages: 1027-1034, Published: 2008 ASMEDC
    Micromodel is small-scale artificial model of porous medium which is known as a novel approach for simulating flow and transport in porous media. For better understanding the effect of fracture geometrical properties on oil recovery efficiency, a series of first contact miscible solvent injection process were conducted on horizontal glass micromodels at several fixed flow rate conditions. The micromodels were initially saturated with the heavy crude oil. The produced oil as a function of injected volume of solvents was measured using image analysis of the provided pictures. The concentration calibration curves of solvents in heavy crude oil were used for evaluating the solvents concentration. Several fractured and non-fractured quarter five-spot micromodels were generated by chemically etching process. The result of the experiments show that the produced oil decreased when the flow rate, fracture spacing, fracture discontinuity, fracture overlap, and fracture distribution were increased. In contrast, the produced oil increased, when the solvent viscosity, fracture orientation angles, fracture discontinuity-distribution and the number of fracture were increased. In addition, an optimum solvent composition is proposed.

  • Feasibility study of auto ignition in in-situ combustion process
    Samaneh Razzaghi, Riyaz Kharrat, Shapour Vossoughi, and Davood Rashtchian

    Journal of the Japan Petroleum Institute, ISSN: 13468804, eISSN: 1349273X, Pages: 287-297, Published: 2008 Japan Petroleum Institute
    Air injection, and the resulting in-situ combustion process, utilizes an inexpensive injectant, air, in order to accelerate oil recovery and increase reserves. Under appropriate conditions, when air is injected into the reservoir, a small amount of the in-place oil is consumed, while the rest is displaced, banked and eventually produced. Moreover, because of the complexity of in-situ combustion processes, their design must be preceded by extensive laboratory investigations to ascertain the burning characteristics of the crude, fuel availability and air requirements. The complexity of the processes has also hindered the development of accurate numerical simulators for performance prediction. Usually, long term investigations and studies are conducted before choosing a reservoir for this process. One of the most important parts of these studies is the feasibility study. Feasibility studies are carried out in order to understand whether the process is possible on the rock and oil of the field. Combustion tube tests and other thermo metric tests like TGA and DSC are usually used to test the feasibility of a process1). Several parameters are either measured or calculated after each test2),3). This work was carried out to determine whether auto ignition process is feasible in this KEM reservoir or not. The first aim was to investigate the risk of carbonate decomposition due to high temperature. To reach this point TGA test on rock and mixture of carbonate rock and KEM oil was done. Moreover, combustion tube tests were conducted using KEM oil and rock. A combustion tube test is a dynamic experiment that mim287 Journal of the Japan Petroleum Institute, 51, (5), 287-297 (2008)

  • Online LQG stabilization of unstable gas-lifted oil wells
    Esmaeel Jahanshahi, Karim Salahshoor, and Riyaz Kharrat

    Computer Aided Chemical Engineering, ISSN: 15707946, Pages: 381-386, Published: 2008 Elsevier
    Abstract The proposed strategies for stabilization of gas-lifted oil wells are offline methods which are unable to track online dynamic changes of the system. However, system parameters such as flow rate of injected gas and also noise characteristic are not constant with respect to time. An adaptive Linear Quadratic Gaussian (LQG) approach is presented in this paper in which the state estimation is performed using an Adaptive Unscented Kalman Filter (AUKF) to deal with unknown time-varying noise statistics. State-feedback gain is adaptively calculated based on Linear Quadratic Regulator (LQR). Finally, the proposed control scheme is evaluated on a simulation case study.

  • Predicting void wave instability in gas-lifted wells
    E. Jahanshahi, K. Salahshoor, and R. Kharrat

    2008 3rd International Symposium on Communications, Control, and Signal Processing, ISCCSP 2008, Pages: 1389-1394, Published: 2008 IEEE
    Oil well instabilities cause production losses. One of these instabilities, referred to as the "void-wave" is an oscillatory phenomenon occurring in gas-lift oil wells. A modified distributed delay model for this dynamic is presented in this paper. Then, the proposed model is used for stability analysis of a hypothetic gas-lift oil well undergoing this type of instability. Stability analysis is performed via small gain theorem and simulations are done using a realistic multiphase flow simulator. Resulting model and its corresponding stability margin are more consistent with well operation facts, compared to the results from the previous works.

  • Investigation of auto ignition condition under different parameters
    Iranian Journal of Chemistry and Chemical Engineering, ISSN: 10219986, Pages: 93-101, Published: June 2008

  • Effect of fracture spacing on VAPEX performance in heavy oil fracture systems
    Iranian Journal of Chemistry and Chemical Engineering, ISSN: 10219986, Pages: 35-45, Published: March 2008

  • Study of the VAPEX process in fractured physical systems using different solvent mixtures
    R. Azin, R. Kharrat, S. Vossoughi, and C. Ghotbi

    Oil and Gas Science and Technology, ISSN: 12944475, Pages: 219-227, Published: March 2008 EDP Sciences
    In this work, the vapour extraction (VAPEX) process is studied experimentally in a rectangular physical model at moderate-high pressure. The solvent was either pure propane or a mixture of propane/methane with different compositions. The solvent and carrier gas were totally mixed before injection, so that a solvent with the desired composition flowed through the injector during experiments, and the solvent mixture was in thermodynamic equilibrium before injection into VAPEX cell. Effects of pressure and composition of solvent were studied. Results showed that at a fixed pressure, the process is more effective with pure solvent compared to the use of solvent mixtures. The main feature of this work is that heavy oil recovery is improved as the approach pressure, defined as the (saturation) pressure minus operating pressure, decreases regardless of solvent composition or operating pressure. These results provide insight into proper field scale implementation of the VAPEX process.

  • The role of connate water saturation in VAPEX process
    Journal of Canadian Petroleum Technology, ISSN: 00219487, Pages: 8-12, Published: February 2008

  • Feasibility study of the cyclic VAPEX process for low permeable carbonate systems
    Mostafa Feali and R. Kharrat

    International Petroleum Technology Conference, IPTC 2008, Pages: 2576-2580, Published: 2008 International Petroleum Technology Conference
    Vaporized hydrocarbon solvents injection in low permeable carbonate systems poses a serious challenge to petroleum engineers as well as a potentially effective and efficient oil recovery method. Thus, there is an incentive for the development of better vaporized solvent injection techniques since heavy oil reservoirs drastically draw attention of huge oil and gas companies. Cyclic VAPEX could be a key tool to achieving economic production from reservoirs containing very viscous oil.

  • Determination of reservoir model from well test data, using an artificial neural network
    Scientia Iranica, ISSN: 10263098, Pages: 487-493, Published: July/August 2008

  • Effect of heterogeneity of layered reservoirs on polymer flooding: An experimental approach using five-spot glass micromodel
    70th European Association of Geoscientists and Engineers Conference and Exhibition 2008: Leveraging Technology. Incorporating SPE EUROPEC 2008, Pages: 1445-1454, Published: 2008

  • Statistical model of dispersion in a 2-D glass micromodel
    Mohammad Hossein Ghazanfari, Riyaz Kharrat, Davood Rashtchian, and Shapour Vossoughi

    Proceedings - SPE Symposium on Improved Oil Recovery, Pages: 527-539, Published: 2008 Society of Petroleum Engineers

  • Simulation study of the VAPEX process in fractured heavy oil system at reservoir conditions
    Reza Azin, Riyaz Kharrat, Cyrus Ghotbi, Behzad Rostami, and Shapour Vossoughi

    Journal of Petroleum Science and Engineering, ISSN: 09204105, Pages: 51-66, Published: January 2008 Elsevier BV
    Abstract The Vapor Extraction (VAPEX) process, a newly developed Enhanced Oil Recovery (EOR) process to recover heavy oil and bitumen, has been studied theoretically and experimentally and is found a promising EOR method for certain heavy oil reservoirs. In this work, a simulation study of the VAPEX process was made on a fractured model, which consists of a matrix surrounded by horizontal and vertical fractures. The results show a very interesting difference in the pattern of solvent flow in fractured model compared with the conventional model. Also, in the fractured system, due to differences in matrix and fracture permeabilities, the solvent first spreads through the fractures and then starts diffusing into matrix from all parts of the matrix. Thus, the solvent surrounds the oil bank, and an oil rather than the solvent chamber forms and shrinks as the process proceeds. In addition, the recovery factor is higher at lower solvent injection rates for a constant pore volume of the solvent injected into the model. Also, the diffusion process becomes important and higher recoveries are obtained at low injection rates, provided sufficient time is given to the process. The effect of inter-connectivity of the surrounding fractures was studied by making the side vertical fractures shorter than the side length of the model. It was observed that inter-connectivity of the fractures affects the pattern of solvent distribution. Even for the case of side fractures being far apart from the bottom fracture, the solvent distribution in the matrix was significantly different than that in the model without fractures. Combination of diffusion phenomenon and gravity segregation was observed to be controlling factors in all VAPEX processes simulated in fractured systems. The early breakthrough of the solvent for the case of matrix surrounded by the fracture partially inhibited diffusion of the solvent into the oil and consequently the VAPEX process became the least effective. It is concluded that fractures of poor connectivity improve the effectiveness of VAPEX process. This is a significant finding for the application of the VAPEX process to the fractured reservoirs.

  • Improved heavy oil recovery by VAPEX process in the presence of vertical and horizontal fractures
    Reza Azin, Riyaz Kharrat, Cyrus Ghotbi, and Shapour Vossoughi

    Journal of the Japan Petroleum Institute, ISSN: 13468804, eISSN: 1349273X, Pages: 340-348, Published: 2007 Japan Petroleum Institute
    Vapor extraction (VAPEX) is an important process for recovery of heavy oil and bitumen. In this work, the VAPEX process is studied experimentally in a rectangular physical model. The setup was constructed in a manner allowing experiments in both fractured and non-fractured systems. Propane was used as the solvent in all experiments. The experiments were conducted with pure solvent and different configurations of fracture-matrix contacts. Effects of pressure and number of side fractures were studied in this work. Results showed that the oil recovery increased with pressure. In addition, we found for the first time that there is a pressure range below the solvent dew point that the process can be performed efficiently. This has an advantage to the process and prevents any pore space blocking in the system due to solvent condensation caused by sudden pressure drops in the connecting lines, as the solvent has the tendency for condensation at conditions near to its dew point pressure. It was also found that the fractures can enhance heavy oil recovery during VAPEX process by improving the contact between solvent and oil contained in the matrix block, increasing the cross flow of solvent and oil between matrix and fracture, and also by providing more area for solvent diffusion into the heavy oil. These findings increase industry confidence for application of VAPEX process in both conventional and fractured reservoirs for exploitation of heavy oil resources.

  • Feasibility study of in-situ combustion in a carbonate reservoir
    SPE Middle East Oil and Gas Show and Conference, MEOS, Proceedings, Pages: 1266-1271, Published: 2007

  • Prediction of permeability reduction rate due to calcium sulfate scale formation in porous media
    SPE Middle East Oil and Gas Show and Conference, MEOS, Proceedings, Pages: 371-376, Published: 2007

  • Capillary pressure estimation using statistical pore size functions
    M. H. Ghazanfari, D. Rashtchian, R. Kharrat, and S. Vossoughi

    Chemical Engineering and Technology, ISSN: 09307516, eISSN: 15214125, Pages: 862-869, Published: July 2007 Wiley
    Capillary pressure curves, which have been employed for a long period of time by researchers interested in pore size distribution, are commonly obtained from experimental measurements. The dynamic capillary pressure that influences the flow is affected by many factors including the pore size characteristics and pore scale dynamics. Hence, it is important to investigate the variation of the estimated pore size distribution with capillary number. In this study, a glass type micromodel is considered as the porous media sample. A parametric probability density function is proposed to express the pore size distribution of the porous model, which is also measured using an image analysis technique. The capillary pressure saturation mathematical model is developed by integrating the pore size distribution function. Model parameters with a physical significance are estimated by fitting the model to the measured capillary pressure data at different capillary numbers. The results of capillary pressure obtained are well matched to the measured values. The results show that the trends of the extracted pore size distribution curves have similar trends, but they are not exactly the same. Therefore, the dynamic capillary pressure data alone are not sufficient for estimation of the pore size distribution. As a related development, the prediction of the capillary pressure curves based on measured pore size distributions is also presented. The proposed probability distribution function has the flexibility of representing a wide variety of pore size distributions.

  • Evaluation of empirically derived PVT properties for Middle East crude oils
    Scientia Iranica, ISSN: 10263098, Pages: 358-368, Published: July/August 2007

  • A correlation approach for prediction of crude-oil PVT properties
    SPE Middle East Oil and Gas Show and Conference, MEOS, Proceedings, Pages: 45-59, Published: 2007

  • The role of connate water saturation in VAPEX process
    S.R. Etminan, B.B. Maini, and R. Kharrat

    Canadian International Petroleum Conference 2007, CIPC 2007, Published: 2007 Petroleum Society of Canada
    Although several successful SAGD and CSS field projects have been reported, the high cost of steam generation, considerable energy loss, need for water and water treatment(1) are some of the problems which necessitate finding a more effective and environmentally friendly recovery method. Meanwhile, solvent-based processes, like VAPEX, have drawn more attention due to their potential advantages. In this process, vapourized light hydrocarbons, like propane and butane or a mixture of these with carrier gases, are used. VAPEX is a solvent analogue of the SAGD process and uses essentially the same well configuration(1). Solvent dissolves into Abstract

  • Experimental study of factors affecting heavy oil recovery in solvent floods
    T. Behrouz, R. Kharrat, and M.H. Ghazanfari

    Canadian International Petroleum Conference 2007, CIPC 2007, Published: 2007 Petroleum Society of Canada

  • Effect of capillarity and surface tension on the performance of VAPEX process
    B. Rostami, S.R. Etminan, A. Soleimani, and R. Kharrat

    Canadian International Petroleum Conference 2007, CIPC 2007, Published: 2007 Petroleum Society of Canada

  • Kinetic study of crude-oil combustion in the presence of carbonate rock
    SPE Middle East Oil and Gas Show and Conference, MEOS, Proceedings, Pages: 393-399, Published: 2007

  • Experimental and computer based simulation study of WAG process
    CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Published: 2006

  • Relative permeability estimation of porous media: Comparison of implicit and explicit approaches
    CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Published: 2006

  • Capillary pressure estimation of porous media using statistical pore size function
    CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Published: 2006

  • Feasibility study of autoignition process in heavy-oil reservoirs
    SPE/PS-CIM/CHOA International Thermal Operations and Heavy Oil Symposium Proceedings, Volume: 2005, Published: 2005

  • Investigation of the Vapex process in high-pressure fractured heavy-oil reservoirs
    Behzad Rostami, Reza Azin, and Riyaz Kharrat

    SPE/PS-CIM/CHOA International Thermal Operations and Heavy Oil Symposium Proceedings, Volume: 2005, Published: 2005 Society of Petroleum Engineers

  • Applicability of the VAPEX process to iranian heavy oil reservoirs
    R. Azin, R. Kharrat, C. Ghotbi, and S. Vossoughi

    SPE Middle East Oil and Gas Show and Conference, MEOS, Proceedings, Pages: 115-125, Published: 2005 Society of Petroleum Engineers

  • Giant oil field formation waters and derivation of a simple empirical colleration for prediction of their related scaling problems
    A. Badakhshan, N. Mohebbi, and R. Kharrat

    Annual Technical Meeting 1998, ATM 1998, Published: 1998 Petroleum Society of Canada

  • Case history of a unique gas injection scheme and its simulation using material balance based simulator
    SPE Proceedings - Gas Technology Symposium, Pages: 515-524, Published: 1996

  • FEASIBILITY STUDY OF THE IN-SITU COMBUSTION PROCESS USING TGA/DSC TECHNIQUES.
    R. Kharrat and S. Vossoughi

    JPT, Journal of Petroleum Technology, ISSN: 01492136, Pages: 1441-1445, Published: Aug Society of Petroleum Engineers (SPE)

  • FEASIBILITY STUDY OF THE IN-SITU COMBUSTION PROCESS USING TGA/DSC TECHNIQUES.
    Society of Petroleum Engineers of AIME, (Paper) SPE, Pages: 471-475, Published: 1984