The Impact of Background Water Flow on CO2 Plume Migration in a Tilted Aquifer

Summary CO2 injection into deep saline aquifers for storage is considered as a promising tool for reducing CO2 emissions. To estimate the storage capacity and assess risks associated with CO2 leakage, an accurate understanding of the post-injection migration, spreading and trapping of the mobile plume of CO2 is crucial. We performed a numerical modelling analysis on the migration of an injected CO2 plume into a dipping aquifer subjected to background water flow, and incorporating residual and dissolution trapping of CO2. We described the plume post-injection migration at different periods, the early and late post-injection periods. Our study focuses on the impact of the background water velocity on the early post-injection migration of the plume. We estimate the height, migration distance and velocity of the plume, and the amount of mobile CO2 within the plume to identify how fast and far it migrates. Our results reveal that as the background velocity increases, the plume migrates further up-dip; however, its height decreases with time. This suggests that the mobile CO2 volume decreases in the aquifer for greater background flow velocities, reducing the risk of leakage. Also, the plume decelerates during its vertical migration and accelerates with background flow velocity during its lateral migration.