Experimental Investigation on the Mechanism of CO ₂ -Enhanced Oil Recovery in Tight Conglomerate Reservoirs with Surfactant Assistance

CO₂ flooding has emerged as a promising enhanced oil recovery method for tight conglomerate reservoirs characterized by low porosity, poor permeability, and ineffective water flooding. However, conventional CO₂ injection often suffers from gravity override and viscous fingering due to insufficient interfacial control, limiting its practical performance. Although previous studies suggest that surfactant-assisted CO₂ flooding can reduce interfacial tension and enhance oil-gas interactions, a comprehensive understanding of the underlying mechanisms remains limited. This study establishes a multiscale experimental framework encompassing wettability alteration, interfacial tension measurements, and core-scale displacement tests to investigate the synergistic enhancement mechanisms of three surfactantsSpan 80, BC, and IPC. Among them, IPC demonstrated superior wettability modification, reducing the contact angle to below 35°, thereby improving rock hydrophilicity. It also exhibited stable interfacial activity across varying temperatures and concentrations, effectively lowering the minimum miscibility pressure while maintaining the interfacial integrity. Core flooding experiments showed that IPC-assisted CO₂ injection significantly increased oil recovery by 27.87%, delayed gas channeling, and stabilized the displacement front compared to BC and Span 80. Injection rate optimization further revealed 0.1 mL/min as the optimal parameter, balancing displacement stability and CO₂ miscibility. Overall, this research elucidates the microscopic interfacial regulation mechanisms of surfactant-assisted CO₂ EOR and confirms the engineering potential of IPC, providing theoretical and technical support for the efficient development of tight oil reservoirs.