Investigation of CO2-EOR and storage mechanism in Injection-Production coupling technology considering reservoir heterogeneity

Heterogeneous reservoirs offer greater potential for increased oil production and carbon storage capacity when using CO2 injection-production coupling technology in a broader range of geological formations. However, the impact of heterogeneity on the mechanisms and effectiveness of CO2 utilization and storage remains unclear. This study comprehensively investigates the mechanisms of enhanced oil recovery and the sequestration potential of CO2 injection-production coupling technology in heterogeneous reservoirs using both microscopic visualization experiments and macroscopic core experiments. The results reveal that during continuous gas flooding, CO2 forms rapid flow channels, leading to the formation of oil films and columnar residual oil in high-permeability zones, while small pores remain unaffected. Meanwhile, under high-speed injection conditions, the overall microscopic recovery rate increases by 13.8%. However, a higher proportion of porous residual oil is retained in low-permeability zones. During asynchronous injection-production cycles, the microscopic recovery rate remains above 86%, indicating a more thorough utilization of porous residual oil, which is predominantly present in membranous and angular corner configurations. The mechanisms of enhanced oil recovery include the increase in energy, dissolution expansion, and displacement-transport mechanisms. In asynchronous injection-production mode, macroscopic recovery rates are all above 80%. Additionally, with an increase in permeability contrast, the CO2 utilization efficiency rises from 5.9% to 8.6%, demonstrating the high potential of injection-production coupling technology for enhanced oil recovery and geological carbon sequestration in heterogeneous reservoirs. This study provides theoretical support for CO2 injection development and geological sequestration in heterogeneous reservoirs.