Performance and displacement efficiency of the surfactant synergistic enhanced inclusion system for high-temperature and high-salinity reservoirs

With continued water injection development, most oilfields have entered high and ultra-high water-cut stages. To address the issue of poor thermal and salt resistance in conventional polymer flooding systems, a salt-tolerant amphiphilic polymer-based supramolecular inclusion system was developed, incorporating a surfactant as a synergistic agent to reduce oil–water interfacial tension (IFT) and further increase system viscosity. In this study, viscosity and oil–water interfacial tension were used as evaluation indicators to optimize the formulation of the surfactant synergistic enhanced inclusion system. The effects of factors such as temperature, inorganic salts, and pH on the apparent viscosity and interfacial tension of the system were systematically examined. Dynamic light scattering and a one-dimensional core physical model were employed to study the emulsification performance and oil displacement efficiency of the system. The results indicate that the surfactant synergistic enhanced inclusion system exhibits excellent thickening ability and IFT reduction under high-temperature and high-salinity conditions (85 °C, 20 × 104 mg·L−1). The rheological properties and IFT reduction capability of the system are both pH-responsive, with optimal performance observed in neutral to alkaline conditions, suggesting a broad application range. The surfactant synergistic enhanced inclusion system not only reduces the water cut but also improves oil-washing efficiency through emulsification, achieving an ultimate recovery rate of 60.13% with an enhanced oil recovery (EOR) of 24.75%. These findings demonstrate that this system is a promising alternative for enhancing oil recovery in high-temperature and high-salinity reservoirs.