Integrating CO2 sequestration and enhanced gas recovery: a comprehensive evaluation for sustainable carbon management

Greenhouse gases pose a significant threat to life on Earth by trapping infrared radiation, leading to global warming. In Bangladesh, carbon dioxide (CO 2 ) emissions have surged by 40% from 2000 to 2020, primarily from the power industry and process sector, making CO 2 the most significant contributor to the country's greenhouse gas inventory. One promising mitigation strategy is the integration of CO 2 sequestration with enhanced gas recovery (CO 2 -EGR-CCUS) in depleted gas reservoirs. This study presents a reservoir simulation-based investigation using CMG software to evaluate the dual objective of maximizing CO 2 storage and recovering residual methane. A comprehensive sensitivity analysis was also performed to assess the impact of well placement, injection rate, and injection pressure on CO 2 injectivity and methane recovery. Among the tested scenarios, staggered well placement with an injection rate of 47 MMSCF/D at 4700 psi yielded the highest gas recovery factor of 4.52%, recovering 1.3 BCF of methane from a depleted gas reservoir with a Gas Initially in Place of 28.8 BCF. The abandoned gas rate was 0.1 × 10⁶ SCF/day, and residual gas saturation was 0.1. The cumulative CO 2 injection reached 3.82 × 10 12 SCF, with 1.36 × 10 12 SCF securely stored under a fracture pressure limit of 6000 psi, as determined using the Pennebaker Correlation. Notably, the project demonstrates a CO 2 capture potential equivalent to 1.24% of Bangladesh’s total annual CO 2 emissions. Staggered well placement also achieved the highest sweep efficiency (12.27%), outperforming linear and five-spot patterns by 3.19% and 2.41%, respectively. These findings highlight the feasibility of combining CO 2 storage with enhanced methane recovery as a scalable and sustainable strategy for carbon management in Bangladesh. The study contributes valuable insights into optimizing CCUS operations under site-specific geological and operational constraints.