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dew-points
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Toward a predictive model for estimating dew point pressure in gas condensate systems
, Article Fuel Processing Technology ; Volume 116 , 2013 , Pages 317-324 ; 03783820 (ISSN) ; Shokrollahi, A ; Gharagheizi, F ; Mohammadi, A. H ; Sharif University of Technology
2013
Abstract
Dew-point pressure is one of the most important quantities for characterizing and successful prediction of the future performance of gas condensate reservoirs. The objective of this study is to present a reliable, computer-based predictive model for prediction of dew-point pressure in gas condensate reservoirs. An intelligent approach based on least square support vector machine (LSSVM) modeling was developed for this purpose. To this end, the model was developed and tested using a total set of 562 experimental data points from different retrograde gas condensate fluids covering a wide range of variables. Coupled simulated annealing (CSA) was employed for optimization of hyper-parameters of...
Investigations of the failure in boilers economizer tubes used in power plants
, Article Journal of Materials Engineering and Performance ; Volume 22, Issue 9 , 2013 , Pages 2691-2697 ; 10599495 (ISSN) ; Mehdipour, M ; Ghorbani, M ; Mohebali, M ; Koohbor, B ; Sharif University of Technology
2013
Abstract
In this study, failure of a high pressure economizer tube of a boiler used in gas-Mazut combined cycle power plants was studied. Failure analysis of the tube was accomplished by taking into account visual inspection, thickness measurement, and hardness testing as well as microstructural observations using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Optical microscopy images indicate that there is no phase transformation during service, and ferrite-pearlite remained. The results of XRD also revealed Iron sulfate (FeSO4) and Iron hydroxide sulfate (FeOH(SO4)) phases formed on the steel surface. A considerable amount of Sulfur was also...
Mathematical Modeling of Molecular Diffusion for Gas Injection of Fractured Gas Condensate Reservoir – Single Block Approach
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Cyrus (Supervisor) ; Gerami, Shahab (Supervisor) ; Hashemi, Abdonabi (Supervisor)
Abstract
Gas condensate reservoirs show very complex behavior as wellbore pressure falls below the reservoir fluid dew point pressure and consequently liquid phase appears near the wellbore. Since pressure drawdown is the largest near the wellbore, therefore, this region is the first that experience the liquid dropouts. With continuing the production, reservoir pressures at the other parts of the reservoir fall below the dew point pressure and as a result, condensate appears at these regions. The more the condensate accumulates near the wellbore the more decreasing the gas relative permeability occurs. Condensate accumulating does as a liquid barrier and causes not only decreasing the gas production;...
Evolving an accurate model based on machine learning approach for prediction of dew-point pressure in gas condensate reservoirs
, Article Chemical Engineering Research and Design ; Vol. 92, issue. 5 , May , 2014 , p. 891-902 ; ISSN: 02638762 ; Shokrollahi, A ; Arabloo, M ; Mahdikhani-Soleymanloo, R ; Masihi, M ; Sharif University of Technology
Abstract
Over the years, accurate prediction of dew-point pressure of gas condensate has been a vital importance in reservoir evaluation. Although various scientists and researchers have proposed correlations for this purpose since 1942, but most of these models fail to provide the desired accuracy in prediction of dew-point pressure. Therefore, further improvement is still needed. The objective of this study is to present an improved artificial neural network (ANN) method to predict dew-point pressures in gas condensate reservoirs. The model was developed and tested using a total set of 562 experimental data point from different gas condensate fluids covering a wide range of variables. After a...
Prediction of phase equilibrium of CO2/cyclic compound binary mixtures using a rigorous modeling approach
, Article Journal of Supercritical Fluids ; Vol. 90 , 2014 , pp. 110-125 ; ISSN: 08968446 ; Soroush, E ; Shokrollahi, A ; Bahadori, A ; Sharif University of Technology
Abstract
Vapor liquid equilibrium (VLE) data has significant role in designing processes which include vapor and liquid in equilibrium. Since it is impractical to measure equilibrium data at any desired temperature and pressure, particularly near critical region, thermodynamic models based on equation of state (EOS) are usually used for VLE estimating. In recent years due to the development of numerical tools like artificial intelligence methods, VLE prediction has been find new alternatives. In the present study a novel method called Least-Squares Support Vector Machine (LSSVM) used for predicting bubble/dew point pressures of binary mixtures containing carbon dioxide (CO 2) + cyclic compounds as...
Challenges of fluid phase behavior modeling in Iranian retrograde gas condensate reservoirs
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 37, Issue 6 , Feb , 2015 , Pages 663-669 ; 15567036 (ISSN) ; Asadi, E ; Nasiri, M ; Khajenoori, L ; Masihi, M ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
Production from gas condensate reservoirs requires precise determination of reservoir fluid properties along with their positive impact on real reservoir performance evaluation and fluid in place volume calculation. This fact is particularly important because liquid drop out phenomena occurs as a result of pressure drop due to fluid production and condensate remains in reservoir [Mohebzadeh, 2005. In this study the challenges and problems of fluid phase behavior simulation in southern Iranian retrograde gas condensate reservoirs is discussed. Most of the problems and challenges are inaccuracy of equation of states near the critical point, special conditions and produced fluid flow...
A new multi-sample EOS model for the gas condensate phase behavior analysis
, Article Oil and Gas Science and Technology ; Volume 66, Issue 6 , September , 2011 , Pages 1025-1033 ; 12944475 (ISSN) ; Crespo, F ; Sharif University of Technology
2011
Abstract
Equations of State EOS are vastly being used to predict the phase behavior of reservoir fluids. The accuracy of EOS modeling technique over conventional correlation models would benefit an improved property prediction of these fluids. Once the crude oil or gas condensate fluid system has been probably characterized using limited laboratory tests, its PVT behavior under a variety of conditions can be easily studied. In this paper, the PVT behavior of gas condensate from a reservoir in South Pars retrograde gas field in Iran was modeled using the three-parameter Patel and Teja Equation of State. The multi-sample characterization method is used to arrive at one consistent model for retrograde...
Optimum operating conditions for direct oxidation of H2S in a fluidized bed reactor
, Article World Academy of Science, Engineering and Technology ; Volume 77 , 2011 , Pages 411-415 ; 2010376X (ISSN) ; Kazemeini, M ; Fattahi, M ; Amjadia, A ; Sharif University of Technology
Abstract
In this research a mathematical model for direct oxidization of hydrogen sulfide into elemental sulfur in a fluidized bed reactor with external circulation was developed. As the catalyst is deactivated in the fluidized bed, it might be placed in a reduction tank in order to remove sulfur through heating above its dew point. The reactor model demonstrated via MATLAB software. It was shown that variations of H 2S conversion as well as; products formed were reasonable in comparison with corresponding results of a fixed bed reactor. Through analyzing results of this model, it became possible to propose the main optimized operating conditions for the process considered. These conditions included;...
Optimum operating conditions for direct oxidation of h 2s in a fluidized bed reactor
, Article World Academy of Science, Engineering and Technology ; Volume 79 , 2011 , Pages 237-241 ; 2010376X (ISSN) ; Kazemeini, M ; Fattahi, M ; Amjadian, A ; Sharif University of Technology
2011
Abstract
In this research a mathematical model for direct oxidization of hydrogen sulfide into elemental sulfur in a fluidized bed reactor with external circulation was developed. As the catalyst is deactivated in the fluidized bed, it might be placed in a reduction tank in order to remove sulfur through heating above its dew point. The reactor model demonstrated via MATLAB software. It was shown that variations of H 2S conversion as well as; products formed were reasonable in comparison with corresponding results of a fixed bed reactor. Through analyzing results of this model, it became possible to propose the main optimized operating conditions for the process considered. These conditions included;...