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چکیده
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Fractured aquifers, such as limestones and dolomites are suitable candidates for carbon sequestration and disposal for environmental protection. For evaluating this process, simulation of acid gas dissolution in fractured aquifer reservoirs is performed. Accurate description of thermodynamic and transport properties of acid gases and brine is required to predict water content and solubility of acid gases. In simulation of density-induced convection, developing an accurate thermodynamic model is necessary to estimate the onset of convection, rate of convective mixing and minimizing the risks of acid gas storage. In this thesis, first, thermodynamics of acid gases and water is modeled by using Winprop software. Then, density-induced convection is simulated in a conventional aquifer. Time-step size and optimal grid block size of such a problem are found by the common criteria of numerical simulation i.e. limiting Peclet and Courant number. The effect of different permeabilities and porosities of rocks are investigated. It is shown that by increasing the porosity, the rate of dissolution decreases and permeability increment accelerates the onset of convection and the rate of mixing, which can be regarded as the main parameters to be considered in the selection of storage sites. The result of this study shows that the location of horizontal fractures and spacing between vertical fractures are the most important factors on the onset of natural convection. Also, the presence of fracture in the aquifers has a significant effect on the mixing process. Fractured aquifers can be considered as an appropriate choice for the selection of storage sites, provided that seal integrity of cap rock is assured
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