Numerical simulations of geological CO2 storage in a gas reservoir of the B depression, Pearl River Mouth Basin

Geological CO 2 storage is a promising strategy for reducing greenhouse gas emissions and has become a growing focus of research and deployment. This paper presents numerical simulations of CO 2 injection and storage in a depleted gas reservoir within the B Depression and evaluates associated CO 2 trapping mechanisms. In the base case, a constant injection rate of 3500 m 3 /d over fifteen years resulted in a cumulative injection of 19.2 × 10 6 m 3 . The CO 2 plume expanded radially during injection and subsequently migrated up-dip under buoyancy forces. The final stored mass of CO 2 in the reservoir was 10.6 million tonnes (Mt), representing less than 10% of its theoretical capacity. The plume was projected to reach the entrapment crest and the top of the reservoir within a century, indicating secure long-term containment. Structural, stratigraphic, and residual trapping dominate in Reservoir A (approximately 90%). Anticlinal closures with thick overlying mudstones in the Zhujiang Formation provide effective seals, further enhancing storage security. Reservoir properties and heterogeneity play a crucial role in controlling CO 2 storage. However, reservoir heterogeneity exerts only a limited influence when intrinsic properties are favorable. Overall, the study and implementation of CO 2 capture, utilization, and storage (CCUS) in China's offshore basins show promising prospects.