Upscaling studies of diffusion induced convection in homogeneous and heterogeneous aquifers

Abstract

Abstract The gravitational instability of a diffusive boundary layer in porous media, or diffusion induced convection, has been studied in a number of papers in recent years . This effect is important as it speeds up the dissolution of the CO 2 phase into the aquifer brine by setting up convective mixing. An empirical formula for the dissolution rate per area phase contact is given which can be used for assessing the effect of using large grid blocks in flow simulations. Simulations of diffusion induced convection in barrier type of aquifers are also considered, and it is demonstrated that standard upscaling of vertical permeability can do a fairly good job in representing the model in an anisotropic homogeneous model. For cases with low vertical communication it is seen that convective mixing is more pronounced in the heterogeneous models than in the corresponding anisotropic homogenous models, and the upscaled homogenous model under predict the dissolution rate.