Numerical Simulation of the Effect of Permeability and Injection Flow Rate on CO2 Migration in Aquifers

Aquifer storage technology for CO2 plays a crucial role in achieving carbon emission reduction. Upon injecting CO2 into the saline layer, the complex interaction among CO2, saltwater, and rock initiates a seepage process characterized by multiphase fluid flow. This study quantitatively analyzed the impact of injection flow rate and permeability on principles governing CO2 migration in isotropic and anisotropic reservoirs. The findings indicated that in isotropic reservoirs with a permeability of 3x10(-15), CO2 penetrated the cap rock's top by the 60th year at an injection flow rate q >= 0.1kg/s. As the injection flow rate rose from 0.01 to 0.2 kg/s, the maximum horizontal penetration distance increased by 2.43 times and maximum vertical penetration distance by 1.102 times. The injection flow rate significantly influences the horizontal permeability distance but has a less impact on the vertical permeability distance. Lower permeabilities lead to slower but more persistent CO2 migration, resulting in higher saturation at the monitoring point and longer vertical penetration distances. In anisotropic reservoirs, when the ratio of horizontal-to-vertical permeability of the reservoir was expanded from 1 to 100, at an injection flow rate q=0.02 kg/s, the maximum horizontal penetration distance was increased by 2.125 times. The comprehensive data analysis in this paper will provide important data support and guidance for the application of CO2 storage technology.