Effect of permeability and density difference on convective mixing and storage of CO2 in saline aquifers

Abstract

The density-driven natural convection is believed to have a positive impact on CO2 storage in saline aquifers. In this regard, studying the parameters that influence the onset of convection is crucial for determining the optimal storage location. Here, we conducted a numerical analysis to investigate how the permeability of the porous medium and the density difference between the brine and CO2-brine mixture affect the mixing efficiency, speed, and development of convective fingers. Results showed that greater permeability and density difference result in a faster onset of convection; hence, fluid velocity and mixing efficiency will increase. Moreover, considering CO2 dissolution based solely on Rayleigh number is not entirely accurate. In addition, if there are different permeability and density difference values, even with a constant Rayleigh number, the mixing of CO2 and brine would not be the same.