Optimization of the Development Plan for CO2 Displacement Considering the Synergistic Effects of Oil Production and CO2 Storage in Low-Permeability Oil Reservoirs

Abstract CO2-enhanced oil recovery (CO2-EOR) technology can achieve the dual purposes of oil production and CO2 storage, which has attracted wide attention. However, due to the economic benefits of CO2 capture, utilization, and storage (CCUS) technology, how to maximize enhanced oil recovery and CO2 storage during the CO2 displacement process remains open. Besides, there is little research on the mechanisms of CO2 displacement and storage in low-permeability oil reservoirs under different conditions. This study investigates the synergistic effects of CO2-EOR and geological CO2 storage efficiency under varying injection stages and rates. A comprehensive synergy factor is proposed to evaluate the trade-offs between oil recovery and CO2 storage. The factor incorporates weighted contributions of the oil recovery factor, determined by stage-average recovery degree and oil displacement rates, and the CO2 storage factor, derived from cumulative storage ratio and storage volume. Weight assignments adapt dynamically to project objectives, prioritizing oil recovery during early stages, balanced considerations during intermediate stages, and CO2 storage during later stages. Results reveal distinct performance characteristics across three stages: the CO2-EOR and storage synergy stage, the oil displacement stage, and the CO2 storage stage. At an injection rate of 20000 m3/d, the synergy stage demonstrates peak efficiency with enhanced oil recovery and CO2 storage capacity, attributed to increased formation pressure and improved crude oil mobilization. The displacement stage emphasizes oil recovery, facilitated by reduced viscosity through CO2 dissolution, with optimal performance observed at 15000 m3/d. During the storage stage, CO2 solubility and storage efficiency improve under higher pressure conditions, with reduced gas channeling and effective long-term CO2 storage achieved at 5000 m3/d. Numerical simulations indicate that CO2 injection velocities significantly influence both oil recovery and CO2 storage outcomes. Higher injection rates enhance crude oil displacement and CO2 storage indices, extending reservoir productivity while addressing climate mitigation goals. However, excessive rates lead to gas channeling, necessitating well shut-in strategies to optimize pressure and suppress flow along high-permeability pathways. This study provides critical insights into optimizing CO2-EOR and geological storage strategies, supporting sustainable hydrocarbon recovery and carbon storage initiatives.