Experimental Evaluation of Combined Plugging System for CO2-Improved Oil Recovery and Storage

High-performance CO2-improved oil recovery (IOR) and storage technology is one of the most promising measures for global oilfield companies to achieve zero carbon targets. Due to the severe heterogeneity of most petroleum reservoirs and the significant density difference between CO2 and reservoir fluid, the efficiency of CO2-IOR and storage is usually limited. In this paper, a hightemperature and high-pressure 30 cm core displacement experiment was used to study the CO2 conformance control performance of both the single- and the combined plugging system in long sandstone cores. The single systems evaluated included polymer gels, CO2 foams, and CO2-responsive thickening polymer (CO2RTP) systems. The combined systems were pairwise combinations of the three of them. Results show that the pressure rise and maximum breakthrough pressure of the gel system were the highest among three single-plugging systems. Its plugging efficiency was the highest, reaching 86.13%. At the same time, its gas production reduction rate was also the highest, reaching 95.71%. In the parallel 30 cm core plugging experiments, three combined plugging systems all showed excellent plugging and CO2 conformance improvement performance. Among them, the combined plugging systems containing polymer gels had larger plugging efficiency, and their gas production reduction ratios reached about 90%. Compared with single systems, the combined plugging systems had the advantages of easy injection and in-depth propagation, which can significantly improve CO2 conformance and oil recovery. The research results of this study can provide the experimental understanding and theoretical guidance for the current tricky oilfield problems of CO2 channeling.