Evaluation of Caprock Sealing Performance for CO2 Saline Aquifer Storage: A Numerical Study

The integrity of caprock sealing is a crucial factor in guaranteeing the safety and long-term feasibility of CO2 saline aquifer storage. In this study, we identified three principal mechanisms that give rise to topseal failure: (1) gradual CO2 seepage through the upper cap, (2) capillary seal failure resulting from the pressure increment due to CO2 injection, and (3) localized overpressure causing cap rupture. Through the integration of numerical simulation and geomechanics, this study offers a sealing assessment for the caprock. The thorough analysis of the sealing performance of the Guantao formation reveals that after 2000 years of CO2 injection, the caprock would undergo intrusion by 35 m without any leakage risk. Moreover, investigations into CO2–water–rock interactions suggest that precipitation reactions outweigh dissolution reactions, leading to a decreased permeability and an enhanced sealing performance. The most likely fracture mode identified is shear fracture with a critical caprock fracture pressure of 36.48 MPa. In addition to these discoveries, it is significant to consider ongoing research aimed at enhancing our ability to predict and manage potential risks associated with carbon capture and storage technologies.