Affecting Parameters in Density Driven Convection Mixing in CO2 Storage in Brine

Abstract

Abstract After injecting CO2 into subsurface brine for storage, it will be trapped in the reservoir through various mechanisms. In the beginning, the geological trapping mechanism dominates and the CO2 plume is moving upward below a cap rock. Then brine will imbibe the formation and some parts of the CO2 will be trapped in the pore paces. Later on injected CO2 will dissolve in the brine and increases its density. As a result, the heavier brine will move into deeper parts of the reservoir and density driven convection mixing will occur. This is known as the solubility trapping mechanism. Here in this study, density driven phenomena in CO2 storage in brine and the influencing parameters are the prime targets. We find particularly interesting results for this through Hele-Shaw cell experiments and numerical simulations. Hele-Shaw flow is defined to occur between two parallel flat plates separated by a small gap. In each experiment the cell is filled with fresh water and a shim prevents it to leak. Then liquid with higher density is placed on top. Several tests including water of varying salinity at the top of the cell have been conducted, and the results are interpreted separately and compared with the base experiment. More extensive studies and sensitivity analysis is done based on a simulation model constructed on the reservoir properties of a brine formation, with wide range of affecting parameters, including density differences, permeability variations and the effect of diffusion coefficients. It has been also attempted to investigate the effect of anisotropy and heterogeneity on the CO2 state after injection.