win德赢

Abstract: Surfactant-enhanced carbonated water alternating with CO2 (SCWAG) flooding, which integrates the advantages of surfactants, carbonated water (CW), and CO2, has demonstrated significant potential for the development of low-permeability reservoirs. Nonetheless, the underlying mechanisms of SCWAG enhanced oil recovery require further elucidation. Its CO2 storage performance and pore-scale oil displacement characteristics have not been thoroughly investigated, and the influence of various factors on SCWAG performance remains limited. This study, for the first time, investigates the pore-scale oil displacement characteristics and CO2 storage performance of SCWAG by integrating core flooding experiments and nuclear magnetic resonance scanning. An innovative core-scale 3D heterogeneous numerical model, developed using computed tomography scanning and refined via history matching, enabling reliable SCWAG simulation and facilitating reservoir-scale analysis of factors affecting SCWAG performance. The results demonstrated that SCWAG notably improves both sweep efficiency and oil displacement efficiency, achieving higher recovery and CO2 storage efficiency than other methods. The total recovery reached 76.99%, with individual recoveries of 56.35%, 76.85%, and 87.96% for micropores, mesopores, and macropores, respectively, and CO2 storage efficiency was 57.22%. Permeability contrast exhibited a significant effect on recovery, while CO2 storage efficiency was primarily influenced by the injection rate and water-to-gas ratio. Moreover, the interaction between the water-to-gas ratio and permeability contrast was found to exert a substantial impact on both recovery and CO2 storage efficiency. This study provides novel insights and an in-depth analysis of the SCWAG process, offering practical guidelines for its application in low-permeability reservoirs.