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ABSTRACT: Onset of double-diffusive buoyancy-driven flow resulted from vertical temperature and concentration gradients in a horizontal
layer of a saturated and homogenous porous medium is investigated using amplification factor theory. After injection of CO2 into a deep saline aquifer, the density of the brine saturated with CO2 increases slightly. This increase in density induces natural convection. The effect of geothermal gradient is also considered
in this work as a second incentive for convection and the double-diffusion convection was studied. Linear stability analysis
is used to predict the inception of instabilities and initial wavelength of the convective instabilities. The analysis presented
is applied to acid gas injection (as an analogue for CO2 storage) into saline aquifers in the Alberta basin. It is found that the geothermal gradient does not have significant effect
on the onset of convection for these aquifers. It is shown that the geothermal effects on the onset of natural convection
are negligible as compared to the solutal effects induced by dissolution and diffusion of CO2 in deep saline aquifers. Therefore, the linear stability analysis and the long-term numerical simulation of CO2 sequestration into such saline aquifers may be assumed to be isothermal in terms of natural convection occurrence.
KeywordsNatural convection-Double-diffusion convection-Stability analysis-CO2 Sequestration-Saline aquifers-CO2 Storage
Transport in Porous Media 04/2012; 84(2):441-456. · 1.81 Impact Factor
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ABSTRACT: Traditional dual porosity models do not take into account the effect of matrix block size distribution on the mass transfer between matrix and fracture. In this study, we introduce the matrix block size distributions into an advective-diffusive solute transport model of a divergent radial system to evaluate the mass transfer shape factor, which is considered as a first-order exchange coefficient between the fracture and matrix. The results obtained lead to a better understanding of the advective-diffusive mass transport in fractured porous media by identifying two early and late time periods of mass transfer. Results show that fractured rock matrix block size distribution has a great impact on mass transfer during early time period. In addition, two dimensionless shape factors are obtained for the late time, which depend on the injection flow rate and the distance of the rock matrix from the injection point.
Journal of contaminant hydrology 03/2012; 133:94-107. · 2.01 Impact Factor
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ABSTRACT: Phase behavior study and solvent-saturated phase properties are of crucial importance for heavy oil in situ recovery methods as well as pipeline transportation, surface upgrading, and refining. In this study, the extraction of light components and liquid–liquid equilibrium (LLE) for Athabasca bitumen/ethane systems were studied at ambient temperature over a wide range of pressure. The impact of the ethane-to-bitumen ratio on the physical properties of the saturated phases as well as the partitioning of solvent in each liquid phase was evaluated. The experiments were conducted using a designed pressure–volume–temperature (PVT) apparatus to obtain LLE properties as well as the extraction yield for bitumen/solvent systems. The experimental results indicated the extraction yield increased with increasing initial solvent concentration at all operating conditions. Comparatively, higher bitumen fractions were extracted at higher pressures, considering a constant initial solvent concentration. Increasing either the pressure or solvent-to-bitumen ratio led to higher light component extraction and resulted in a heavier bitumen-enriched phase. Finally, the extraction yield and solubility data for a bitumen/propane system was experimented and compared with those of a bitumen/ethane system at the same conditions. The results revealed that the propane has a greater ability than ethane to extract components from bitumen.
09/2011;
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ABSTRACT: The liquid saturated properties (solubility, density, and viscosity) data for the binary system of ethane + n-tetradecane at three temperatures (323, 373, and 423) K were measured using a designed pressure–volume–temperature (PVT) apparatus. The saturated liquid phase properties were measured for pressures up to 8 MPa. The experimental data (saturated liquid phase composition and density) were compared with the modeling results obtained using the Peng–Robinson and Soave–Redlich–Kwong equations of state.
08/2011;
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ABSTRACT: In this study, we have made an attempt to address how the nanoparticle flows may affect the hydrodynamic instability around a miscible front. In order to explore the role of nanoparticles in such flows, a linear stability analysis was performed to examine the impact of nanoparticle addition for an already unstable miscible displacement. The growth rates of the temporal modes of the instability are determined for different profiles or physical properties of nanoparticles. The results reveal that the diffusion of either the carrier fluids or nanoparticles initially has destabilizing effects, but demonstrates stabilizing effects at longer times, as the cutoff spectrum is initially shifted to larger wavenumbers, but shifted back later. It was found that deposition of nanoparticles into the medium stabilizes the miscible front, such that the maximum growth rates and cutoff wavenumbers increase continuously.
Journal of Applied Physics 06/2011; · 2.17 Impact Factor
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ABSTRACT: Underground coal gasification (UCG) as an efficient method for the conversion of the world’s coal resources into energy, liquid fuels, and chemicals has attracted lots of attention in recent years. This paper is concerned with a feasibility study of the UCG process for Alberta reservoirs using the three-dimensional simulation of this process based on a unique porous media approach. The proposed approach combines the effects of heat, mass transport, and chemical reactions to achieve this goal. The Computer Modeling Group (CMG) software STARS is used for simulation. The geological structure including coal and layers interspersed between coal seams (claystone layers), the porosity/permeability variation, and the chemical processes with corresponding parameters are considered in the model. Chemical stoichiometry coefficients of the pyrolysis process are calculated from proximate and extended experimental data. Genetic algorithm and pattern search are used for parameter estimation. This model is developed to study UCG in deep coal seams and can be used for production prediction and optimization of the process. The simulation results, such as cavity formation, temperature profile, and gas composition at the producer, are presented. Finally, the results are analyzed on the basis of field pilot tests.
05/2010;
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ABSTRACT: Carbon dioxide storage in deep saline aquifers is considered a possible option to bring greenhouse gas emissions under control. The understanding of the underlying mechanisms, such as convective mixing and associated mechanisms, affecting this mixing may have an impact on the long-term sequestration process in deep saline aquifers. One of the significant aspects of the flow of miscible species in porous media is velocity dependent dispersion. The effect of dispersion on dissolution of carbon dioxide (CO2) into brine is investigated by full nonlinear numerical simulations. This study reveals that dispersion may dramatically change the trend of CO2 dissolution into brine. It was found that the dissolution of CO2 increases as dispersion strength increases. The mixing pattern also shows three different mechanisms: diffusion, convection, and a highly nonlinear interaction mechanism. However, the medium dispersivity ratios were found to slightly affect the mixing, while having an impact on the fingering pattern. © 2010 American Institute of Chemical Engineers AIChE J, 2011
AIChE Journal 05/2010; 57(3):561 - 570. · 2.26 Impact Factor
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SPE Reservoir Evaluation & Engineering - SPE RESERV EVAL ENG. 01/2009; 12(5):737-744.
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ABSTRACT: In situ catalytic upgrading of heavy oil and bitumen has been suggested and tested in the laboratory for utilization of heavy oil resources. Experimental observations have demonstrated potential, so this innovative recovery technique may have a role in the development of large resources of heavy oil and bitumen. Accurate analytical and numerical modelling is necessary in order to correctly interpret experimental measurements of the in situ upgrading, leading to a better understanding and design of field-scale processes. In this paper, we present modelling and parameter estimation for ultra-dispersed catalytic upgrading experiments conducted in a batch reactor. The Monte Carlo simulation technique was used to estimate the most appropriate reaction parameters. The combination of an analytical batch reactor model and the Monte Carlo simulation technique allows for the fast generation of a large number of upgrading experiment realizations. Comparisons of analytical modelling results with the experimental measurements of the upgrading experiments at different temperatures are in close agreement. Results reveal that ultra-dispersed catalytic upgrading in a batch reactor results in a fairly high residue conversion and can potentially increase the API gravity of the produced oil.
Fuel. 89(10):2822-2828.
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ABSTRACT: Heterogeneous gas–solid reactions play an important role in a wide variety of engineering problems. Accurate numerical modeling is essential in order to correctly interpret experimental measurements, leading to developing a better understanding and design of industrial scale processes. The exothermic nature of gas–solid reactions results in large concentration and temperature gradients, leading to steep reaction fronts. Such sharp reaction fronts are difficult to capture using traditional numerical schemes unless by means of very fine grid numerical simulations. However, fine grid simulations of gas–solid reactions at large scale are computationally expensive. On the other hand, using coarse grid block simulations leads to excessive front dissipation/smearing and inaccurate results. In this study, we investigate the application of higher-order and flux-limiting methods for numerically modeling one-dimensional coupled heat and mass transfer accompanied with a gas–solid reaction. A comparative study of different numerical schemes is presented. Numerical simulations of gas–solid reactions show that at low grid resolution which is of practical importance Superbee, MC, and van Albada-2 flux limiters are superior as compared to other schemes. Results of this study will find application in numerical modeling of gas–solid reactions with Arrhenius type reaction kinetics involved in various industrial operations.
Computers & Chemical Engineering.
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ABSTRACT: Activated carbons were prepared through chemical activation of corn cob precursor, using potassium hydroxide as the chemical agent. The effect of different parameters, such as particle size, method of mixing, chemical/corn ratio, activation time and activation temperature, on weight loss and BET surface area of the produced activated carbons were discussed. The porosity of the activated carbons was evaluated through nitrogen adsorption. The storage capacity of the activated carbon was evaluated using natural gas. Under the experimental conditions investigated, the optimal conditions for production of high surface area carbons by chemical activation were identified. The results were compared with commercial activated carbons from coal.
Chemical Engineering Research and Design 87(8):1059-1064. · 1.97 Impact Factor
