Review and Future Perspectives of CO 2 Flooding-Storage Synergy in Low-Permeability Reservoirs: Influencing Factors and Optimization Techniques

Under the background of the increasing contradiction between global energy demand and environmental protection, the development of low-permeability reservoirs and the utilization of CO 2 have become important technical means to coordinate energy security and climate governance. The current progress in the application of CO 2 for low-permeability reservoirs is described systematically in this paper. From the perspective of oil displacement mechanisms, the effect of multiple micromechanisms such as reducing crude oil viscosity, inducing volume expansion, enhancing diffusion effect, and regulating interfacial tension on oil recovery are analyzed. The effects of key reservoir parameters such as pressure, permeability, and fracture structure on the oil displacement process are discussed. On this basis, new synergistic technologies such as CO 2 -thickened composites, chemical assistance, and ultrasonic assistance are further introduced. In terms of oil flooding-storage synergy, this paper reveals the synergistic mechanism of CO 2 in low-permeability reservoirs and demonstrates the effects of reservoir conditions, injection strategies, and pressure control on the stability of oil flooding-storage. The potential of new synergistic paths such as N 2 -assisted nanomaterial modification and CO 2 microbubbles is also evaluated. The key challenges faced by the technology in practical applications are summarized, and future research directions are prospected. It is expected to provide a theoretical basis and engineering reference for deepening the understanding of the behavior mechanism of CO 2 in low-permeability reservoirs and promoting the development of integrated technologies of flooding and storage.