CO2 Injection for Enhanced Recovery and Storage in Fractured Bottom-Water Gas Reservoir—A Case Study of the B9 Gas Field

Fractured bottom-water gas reservoirs are prone to water channeling during production, leading to gas well flooding and reduced recovery. This study takes the B9 gas reservoir in the Tarim Basin as the research object and employs numerical simulation methods to conduct collaborative optimization research on early water invasion prevention and CO2 injection for enhanced recovery. Firstly, reasonable gas production rates and water-avoidance heights are optimized to determine the optimal development scheme. Then, the CO2 injection location and rate are systematically optimized to establish the optimal injection scheme. The research results indicate that the highest recovery factor of 32.3% is achieved when the field production rate is 2%, the water-avoidance height is 80 m, gas injection is performed at the water invasion front, and the injection rate is 15 × 104 m3/d. Under this optimal scheme, the CO2 storage volume reaches 585.6 × 106 m3, with a storage ratio of 44.2%, of which dissolved storage accounts for 24.5 × 106 m3 and structural storage accounts for 561.1 × 106 m3. The research findings provide a technical reference for the synergistic development of early water invasion prevention and CO2 injection for enhanced recovery and storage in fractured bottom-water gas reservoirs.