Research on CO2 sequestration in saline aquifers with different relative permeability considering CO2 phase conditions

Saline aquifers are the most feasible potential site for the storage of CO2. The behavior of CO2 in different phase states may significantly affect the flow properties and sequestration efficiency. It is important to understand and predict the effects of different CO2 phases. This study conducted relative permeability tests under two experimental conditions with CO2 in different phases. Incorporating experimental data into reservoir-scale simulations to analyze the effects of different phases of CO2 on structural, solubility, and residual sequestration mechanisms, and to predict CO2 behavior in saline aquifers. The results show that the CO2 relative permeability and residual CO2 saturation are high under supercritical conditions. It is more favorable to consider the relative permeability and hysteresis effects on the supercritical CO2 results, with a more dispersed distribution of CO2 at the bottom of the reservoir. There was a significant difference in residual sequestration, with the gaseous group showing a 14.16 % reduction in residual sequestration and a 4.27 % reduction in total sequestration compared to the supercritical group. The ratio of structural sequestration, solubility sequestration, and residual sequestration in the total sequestration in this study is about 50 %:30 %:20 %.