Numerical Simulation of Natural Convection in Heterogeneous Porous media for CO 2 Geological Storage

Abstract

We report a modeling and numerical simulation study of density-driven natural convection during geological CO 2 storage in heterogeneous formations. We consider an aquifer or depleted oilfield overlain by gaseous CO 2, where the water density increases due to CO 2 dissolution. The heterogeneity of the aquifer is represented by spatial variations of the permeability, generated using Sequential Gaussian Simulation method. The convective motion of the liquid with dissolved CO 2 is investigated. Special attention is paid to instability characteristics of the CO 2 concentration profiles, variation of mixing length, and average CO 2 mass flux as a function of the heterogeneity characterized by the standard deviation and the correlation length of the log-normal permeability fields. The CO 2 concentration profiles show different flow patterns of convective mixing such as gravity fingering, channeling, and dispersive based on the heterogeneity medium of the aquifer. The variation of mixing length with dimensionless time shows three separate regimes such as diffusion, convection, and second diffusion. The average CO 2 mass flux at the top boundary decreases quickly at early times then it increases, reaching a constant value at later times for various heterogeneity parameters. © 2012 The Author(s).