Investigation of different caprock morphologies on CO leakage and solubility trapping mechanism.

A thorough understanding of subsurface formation zones is critical for safe and long-term storage using CO₂ geological sequestration (CGS). A major concern in CGS is the risk of CO₂ leakage due to plume migration through structural faults and cracks in the caprock. This research investigates the effects of caprock morphologies on CO₂ plume migration, solubility trapping, and leakage risks using multiphase multicomponent reactive transport simulations. Three synthetic domains with varying caprock morphologies are modelled, incorporating geological subsurface features. The study reveals that the presence of cracks significantly impacts CO₂ entrapment and leakage. In the current analysis outcomes, in comparison between the synthetic domain-1 and - 2, due to the presence of an anticline structure in synthetic domain-1 reduced sweeping efficiency by 25%, which in turn influenced solubility trapping, with leakage recorded 15% lower in synthetic domain-2 compared to domain-1. In contrast, synthetic domain-3, based on the Deccan traps stairsteps morphology, showed 30% less leakage despite injecting 21.6 Mt of CO₂, compared to the 18.9 Mt injected into domains 1 and 2. This is due to the enhanced CO₂ plume migration through stairstep traps in the lateral direction, which promoted primary trapping followed by solubility trapping. The findings highlight the importance of geological structures in determining CO₂ migration patterns, sweeping efficiency, and leakage risks, contributing to the optimization of CO₂ storage strategies. These insights are critical for addressing gaps in CGS implementation and ensuring the safe and efficient sequestration of CO₂ over the long term.