Optimization of CO2-EOR and geological sequestration in sandstone reservoirs via sensitivity analysis and metaheuristic algorithms

This study develops a framework for CO 2 -enhanced oil recovery (EOR) and carbon sequestration in a sandstone reservoir, targeting carbon neutrality. Cumulative oil production ( COP ), CO 2 geological sequestration ( CO 2 GS ), and net present value ( NPV ) were optimized by using CMG-GEM simulations, sensitivity analysis, and optimization techniques including particle swarm optimization (PSO), differential evolution (DE), and Latin hypercube sampling with proxy (LHSP) via CMG-CMOST. Sensitivity analysis evaluates matrix permeability, CO 2 injection rates, CO 2 -to-water ratios, and well patterns, while PSO optimizes injection rates, bottom-hole pressures, and durations. Three strategies, namely water-alternating-gas (WAG), gas after water (GAW), and continuous CO 2 injection, were tested over a 50-year period. Lower permeability enhances CO 2 retention capacity but limits oil recovery, whereas higher permeability boosts oil production—with a 19% increment at 10× baseline permeability—yet risks CO 2 breakthrough. An optimal injection rate of 1 PV/yr yields 302 053 m 3 oil and 197 × 10 6 m 3 CO 2 stored. A 1:1 CO 2 -to-water ratio maximizes sweep efficiency, and the four-five-spot pattern delivers 19% higher oil recovery than the base case. A comparison between PSO, DE, and LHSP shows that PSO outperforms the other two optimization methodologies. Optimization with PSO achieves an incremental oil production of 41 000 m 3 and an additional CO 2 storage of 119 × 10 6 m 3 over the base case, with an NPV of $82.25 million. Among the three injection strategies (WAG, GAW, and continuous CO 2 injection), PSO-optimized WAG demonstrates the most effective balance, improving oil recovery factor by up to 19% and significantly enhancing CO 2 storage. Weighting analysis shows that a balanced weighting ( = 0.5) optimizes both objectives, with Sobol analysis identifies gas injection timing as the dominant factor influencing NPV , underscoring the importance of precise operational timing. This framework enhances Carbon Capture, Utilization, and Storage (CCUS) efficiency, surpassing traditional EOR methods in technical, economic, and environmental synergy. • Integrated CO 2 -EOR and sequestration optimization via particle swarm optimization. • Comprehensive sensitivity analysis of injection rates, patterns, and gas-water ratios. • Trade-off evaluation: Oil recovery maximization vs. CO 2 storage efficiency. • Optimized strategies enhanced NPV , CO 2 storage, and oil recovery by up to 19%. • Framework tailored for sustainable CCUS operations in sandstone reservoirs.