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    Experimental determination of equilibrium interfacial tension for nitrogen-crude oil during the gas injection process: The role of temperature, pressure, and composition

    , Article Journal of Chemical and Engineering Data ; Vol. 59, issue. 11 , September , 2014 , p. 3461-3469 ; ISSN: 00219568 Hemmati-Sarapardeh, A ; Ayatollahi, S ; Zolghadr, A ; Ghazanfari, M. H ; Masihi, M ; Sharif University of Technology
    Abstract
    Nitrogen has emerged as a competitive gas injection alternative for gas-based enhanced oil recovery processes in the past two decades. The injection of nitrogen into the reservoirs has improved the oil recovery efficiency in various oil reservoirs from heavy to volatile oils. As it is known, interfacial tension (IFT) plays a key role in any enhanced oil recovery process, particularly gas injection processes; therefore, its accurate determination is crucial for the design of any gas injection process especially at reservoir condition. In this study, an axisymmetric drop shape analysis (ADSA) was utilized to measure the equilibrium IFTs between crude oil and N2 at different temperature levels... 

    Phase behavior modeling of asphaltene precipitation for heavy crude including the effect of pressure and temperature

    , Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Vol. 36, issue. 19 , Feb , 2014 , p. 2087-2094 ; ISSN: 15567036 Tavakkoli, M ; Ghazanfari, M. H ; Masihi, M ; Kharrat, R ; Sharif University of Technology
    Abstract
    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... 

    Experimental determination of interfacial tension and miscibility of the CO2-crude oil system; Temperature, pressure, and composition effects

    , Article Journal of Chemical and Engineering Data ; Vol. 59, issue. 1 , December , 2014 , p. 61-69 ; ISSN: 00219568 Hemmati-Sarapardeh, A ; Ayatollahi, S ; Ghazanfari, M. H ; Masihi, M ; Sharif University of Technology
    Abstract
    Interfacial tension (IFT) as one of the main properties for efficient CO2 flooding planning in oil reservoirs depends strongly on pressure, temperature, and composition of the reservoir fluids. Therefore, it is important to measure this property at real reservoir conditions for successful field development plan. In this study, an axisymmetric drop shape analysis (ADSA) has been utilized to measure the equilibrium IFTs between crude oil and CO2 at different temperatures and pressures. Moreover, minimum miscibility pressures (MMP) and first-contact miscibility pressures (P max) of crude oil/CO2 systems at different temperatures are determined by applying the vanishing interfacial tension (VIT)... 

    Phase behavior modeling of asphaltene precipitation for heavy crudes: A promising tool along with experimental data

    , Article International Journal of Thermophysics ; Vol. 33, issue. 12 , December , 2012 , p. 2251-2266 ; ISSN: 0195928X Tavakkoli, M ; Kharrat, R ; Masihi, M ; Ghazanfari, M. H ; Fadaei, S ; Sharif University of Technology
    Abstract
    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... 

    Prediction of asphaltene precipitation during solvent/CO2 injection conditions: A comparative study on thermodynamic micellization model with a different characterization approach and solid model

    , Article Journal of Canadian Petroleum Technology ; Vol. 50, issue. 3 , March , 2011 , p. 65-74 Tavakkoli, M ; Masihi, M ; Ghazanfari, M. H ; Kharrat, R ; Sharif University of Technology
    Abstract
    There are different thermodynamic models that have been applied for modelling of asphaltene precipitation caused by various reasons, such as solvent/CO2 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... 

    Prediction of asphaltene precipitation during pressure depletion and CO2 injection for heavy crude

    , Article Petroleum Science and Technology ; Vol. 28, issue. 9 , Mar , 2009 , p. 892-902 ; ISSN: 10916466 Tavakkoli, M ; Kharrat, R ; Masihi, M ; Ghazanfari, M. , H ; Sharif University of Technology
    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... 

    Modeling of asphaltene deposition during miscible CO2 Flooding

    , Article Petroleum Science and Technology ; Vol. 32, Issue. 18 , 2014 , Pages 2183-2194 ; ISSN: 10916466 Tahami, S. A ; Dabir, B ; Asghari, K ; Shahvaranfard, A ; Sharif University of Technology
    Abstract
    The authors present the results of numerical tests and simulations to investigate and analyze the likelihood of asphaltene precipitation and deposition during CO2 flooding in a reservoir. The effects of asphaltene precipitation on oil properties such as oil viscosity and density during miscible CO2 flooding process were elaborated by using Winprop software of Computer Modeling Group. Also oil properties change during CO 2 miscible flooding by numerical slim tube were investigated by a compositional simulator (GEM). A fluid sample of Saskatchewan Reservoir that had been flooded miscibly with CO2 was chosen for performing the sensitivity analyses. The results showed that asphaltene... 

    Effects of paraffinic group on interfacial tension behavior of CO 2-asphaltenic crude oil systems

    , Article Journal of Chemical and Engineering Data ; Vol. 59, issue. 8 , 2014 , Pages 2563-2569 ; ISSN: 00219568 Mahdavi, E ; Zebarjad, F. S ; Taghikhani, V ; Ayatollahi, S ; Sharif University of Technology
    Abstract
    The interfacial tension (IFT) of a crude oil/CO2 system is recognized as the main property affecting the efficiency of CO2 flooding during an enhanced oil recovery (EOR) process. The addition of a paraffin group hydrocarbon to asphaltenic crude oils as an asphaltene precipitant component is aimed to mimic the asphaltene precipitation process during crude oil production and transportation. Asphaltene precipitation would critically affect the interfacial behavior of crude oil/CO2 systems. In the first part of this study, the equilibrium densities of oil samples which contain n-heptane at different ratios were measured over varying pressures at 323 K. Then, the equilibrium IFT between CO2 and... 

    Experimental and modelling investigations of asphaltene precipitation during pressure depletion and gas injection operations

    , Article Petroleum Science and Technology ; Vol. 32, issue. 15 , August , 2014 , pp. 1868-1875 ; ISSN: 10916466 Nakhli, H ; Alizadeh, A ; Afshari, S ; Kharrat, R ; Ghazanfari, M ; Sharif University of Technology
    Abstract
    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... 

    Experimental study of asphaltene precipitation behavior during miscible carbon dioxide injection

    , Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Vol. 36, issue. 14 , July , 2014 , pp. 1523-1530 ; ISSN: 15567036 Alizadeh, A ; Nakhli, H ; Kharrat, R ; Ghazanfari, M. H ; Aghajani, M ; Sharif University of Technology
    Abstract
    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... 

    Asphaltene deposition in different depositing environments: Part 2. Real oil

    , Article Energy and Fuels ; Vol. 28, Issue. 6 , 2014 , Pages 3594-3603 ; ISSN: 08870624 Tavakkoli, M ; Panuganti, S. R ; Taghikhani, V ; Pishvaie, M. R ; Chapman, W. G ; Sharif University of Technology
    Abstract
    This paper is a continuation of our previous paper (part 1; 10.1021/ef401857t), which discussed the roles of different phenomena effecting the deposition of asphaltene from model oil systems and before the onset of asphaltene precipitation. The study in this paper is to understand the depositional tendency of asphaltene using a quartz crystal microbalance with dissipation (QCM-D) measurements and their corresponding modeling for real crude oil systems with emphasis after the onset of asphaltene precipitation  

    A core scale investigation of Asphaltene precipitation during simultaneous injection of oil and CO2: An experimental and simulation study

    , Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Vol. 36, issue. 10 , Dec , 2014 , pp. 1077-1092 ; ISSN: 15567036 Bagherzadeh, H ; Rashtchian, D ; Ghazanfari, M. H ; Kharrat, R ; Sharif University of Technology
    Abstract
    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.... 

    Asphaltene deposition in different depositing environments: Part 1. model oil

    , Article Energy and Fuels ; Vol. 28, Issue. 3 , 2014 , pp. 1617-1628 ; ISSN: 08870624 Tavakkoli, M ; Panuganti, S. R ; Vargas, F. M ; Taghikhani, V ; Pishvaie, M. R ; Chapman, W. G ; Sharif University of Technology
    Abstract
    Among the asphaltene flow assurance issues, the most major concern because of asphaltene is its potential to deposit in reservoir, well tubing, flow lines, separators, and other systems along production lines causing significant production losses. Hence, the focus of this study is to understand the depositional tendency of asphaltene using quartz crystal microbalance with dissipation (QCM-D) measurements. The results are presented in two consecutive papers, with this paper (part 1) dealing with model oil systems. The depositing environment is varied by changing the system temperature, asphaltene polydispersity, solvent (asphaltene stability), depositing surface, and flow rate. This paper... 

    Precipitated asphaltene amount at high-pressure and high-temperature conditions

    , Article Energy and Fuels ; Vol. 28, Issue. 3 , 2014 , pp. 1596-1610 ; ISSN: 08870624 Tavakkoli, M ; Panuganti, S. R ; Taghikhani, V ; Pishvaie, M. R ; Chapman, W. G ; Sharif University of Technology
    Abstract
    In the upstream asphaltene flow assurance community, both academics and industries are actively involved to predict the asphaltene deposit profile in wellbores and pipelines. Essential information for such a study is the amount of asphaltenes that can precipitate and, hence, deposit. In this work, the perturbed chain form of the statistical associating fluid theory (PC-SAFT) is applied to predict the asphaltene precipitation onset condition as well as the amount of precipitate under pressure depletion and high-pressure and high-temperature gas injection conditions. Previous PC-SAFT asphaltene studies in crude oil required the compositional data for both flashed gas and flashed liquid. This... 

    SAFT model for upstream asphaltene applications

    , Article Fluid Phase Equilibria ; Volume 359 , December , 2013 , Pages 2-16 ; 03783812 (ISSN) Panuganti, S. R ; Tavakkoli, M ; Vargas, F. M ; Gonzalez, D. L ; Chapman, W. G ; Sharif University of Technology
    2013
    Abstract
    The increasing incidence of flow assurance problems caused by asphaltene deposition during oil production has motivated the development of numerous theoretical models and experimental methods to analyze this complex phenomenon. Even more challenging are the prediction of the occurrence and the magnitude of asphaltene deposition. It is well accepted that precipitation of asphaltene is a necessary condition for deposition. Hence, a significant amount of work has been devoted to the understanding of the conditions at which asphaltene precipitate from the crude oil. Although, several models seem to work well for correlating available data of onsets of asphaltene precipitation, they usually lack... 

    A modified scaling equation based on properties of bottom hole live oil for asphaltene precipitation estimation under pressure depletion and gas injection conditions

    , Article Fluid Phase Equilibria ; Volume 358 , 2013 , Pages 212-219 ; 03783812 (ISSN) Jafari Behbahani, T ; Ghotbi, C ; Taghikhani, V ; Shahrabadi, A ; Sharif University of Technology
    2013
    Abstract
    The process of asphaltene precipitation has a substantial effect on oil flow during primary oil production and enhanced oil recovery processes in the petroleum industry. In this work, a modified scaling model based on the PVT properties of bottom hole live oil including resin to asphaltene ratio, onset pressure, bubble point pressure, reservoir temperature, asphaltene content of bottom hole live oil and gas to oil ratio has been proposed to account for asphaltene precipitation under pressure depletion/gas injection conditions and the proposed model was verified using experimental data obtained in this work and also with those reported in the literature. In the proposed scaling model the... 

    The gas-oil interfacial behavior during gas injection into an asphaltenic oil reservoir

    , Article Journal of Chemical and Engineering Data ; Volume 58, Issue 9 , 2013 , Pages 2513-2526 ; 00219568 (ISSN) Escrochi, M ; Mehranbod, N ; Ayatollahi, S ; Sharif University of Technology
    2013
    Abstract
    Oil displacement and recovery efficiency during gas injection depends on the competition between driving forces and capillary resistance that is governed by gas-oil interfacial behavior. Detailed study of the interfacial forces during gas injection is the main objective of this research work. The effects of injecting gas composition and the possibility of asphaltene precipitation in a wide pressure range were determined through comprehensive experimental study. This was performed by measurement of interfacial tension of a highly asphaltenic Iranian crude oil in three surrounding gas mediums. The results showed that as pressure increases, the rate to reach miscibility reduces in the vicinity... 

    Asphaltene precipitation due to natural depletion of reservoir: Determination using a SARA fraction based intelligent model

    , Article Fluid Phase Equilibria ; Volume 354 , September , 2013 , Pages 177-184 ; 03783812 (ISSN) Hemmati Sarapardeh, A ; Alipour Yeganeh Marand, R ; Naseri, A ; Safiabadi, A ; Gharagheizi, F ; Ilani Kashkouli, P ; Mohammadi, A. H ; Sharif University of Technology
    2013
    Abstract
    Precipitation of asphaltene leads to rigorous problems in petroleum industry such as: wettability alterations, relative permeability reduction, blockage of the flow with additional pressure drop in wellbore tubing, upstream process facilities and surface pipelines. Experimentally determination of the asphaltene precipitation is costly and time consuming. Therefore, searching for some other quick and accurate methods for determination of the asphaltene precipitation is inevitable. The objective of this communication is to present a reliable and predictive model namely, the least - squares support vector machine (LSSVM) to predict the asphaltene precipitation. This model has been developed and... 

    Assessment of asphaltene deposition due to titration technique

    , Article Fluid Phase Equilibria ; Volume 339 , 2013 , Pages 72-80 ; 03783812 (ISSN) Chamkalani, A ; Amani, M ; Kiani, M. A ; Chamkalani, R ; Sharif University of Technology
    2013
    Abstract
    Due to problems followed by asphaltene deposition, which cause many remedial processes and costs, it seemed necessary to develop equations for determining asphaltene precipitation quantitatively or qualitatively. In this study a new scaling equation as a function of temperature, molecular weight, and dilution ratio (solvent) has been developed. This equation can be used to determine the weight percent of precipitated asphaltene in the presence of different precipitants (solvents). The proposed methodology utilizes least square support vector machines/regression (LSSVM/LSSVR) to perform nonlinear modeling. This paper proposes a new feature selection mechanism based on coupled simulated... 

    Phase behavior modeling of asphaltene precipitation for heavy crudes: A promising tool along with experimental data

    , Article International Journal of Thermophysics ; Volume 33, Issue 12 , December , 2012 , Pages 2251-2266 ; 0195928X (ISSN) Tavakkoli, M ; Kharrat, R ; Masihi, M ; Ghazanfari, M. H ; Fadaei, S ; Sharif University of Technology
    2012
    Abstract
    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...