Numerical simulation of CO2 Sequestration in saline aquifer influenced by heterogeneous capillary pressure and wettability

Abstract

CO2 sequestration in saline aquifer is an immediately applicable option to reduce atmospheric emissions of CO2. This study covers quantitative assessment of CO2 trapping capacity with residual, dissolution and capillary trapping mechanisms in heterogeneous formations. The effects of heterogeneity on CO2 trapping capacity are studied under different wettability scenarios. Leverett J-function is applied so that every grid block has a different drainage capillary pressure curve, which is physically consistent with its heterogeneous properties and wettability. Based on contact angle, the residual saturation and relative permeability curves are modeled. The results indicate that different heterogeneity and wettability give considerable variations in the leakage of CO2 ranging from 6% to 38%. The lateral correlation length of permeability affects spatial distribution of CO2. As the permeability variation increases, the total amount of CO2 trapped increases significantly, which means potential risk of leakage reduces. Although residual and dissolution trappings decrease as the wetting condition changes from strongly-water wet to intermediate wet, the amount of CO2 trapped by capillary barriers increases considerably and mobile phase saturation of CO2 reduces.