This paper presents an investigation of the density-driven problem that rises during the CO2 sequestration into saline aquifer. The lattice Boltzmann method (LBM) is implemented in a way to solve this mixing problem (the brine problem along with the solute transport). The CO2-brine interface was located at the top of the considered domain. Different Rayleigh numbers were used in order to investigate this problem. When Rayleigh number is low, we got steady-state concentration contours describing a Rayleigh-Bénard type of convection. Moreover, when the Rayleigh number was selected to be big enough, we observe that the system is less stable and a convective fingering is initiated. This instability is caused by a higher density difference between the brine and the sequestrated CO2. Note here that the turbulence is not taken into account in the study. After the onset this convective instability, the brine with a high CO2 concentration migrates down into the porous medium. This study is based on a statistical LBM theory without assuming periodicity in any directions and without considering any type of disturbances in order to turnon the instability behavior.
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