Compound Surfactant System with Superior Oil Displacement Performance: Balanced Synergistic Effects from Oil–Water and Oil–Solid Interfaces

The oil film formed by the adhesion of crude oil to the resin-asphalt adsorption layer is difficult to peel off due to the strong oil-solid interaction, which severely limits further improvements in oil recovery. Although conventional compound oil displacement systems can effectively reduce oil-water interfacial tension, facilitate oil droplet deformation, and alleviate the Jamin effect, they are insufficient in controlling the wettability of oleophilic rock surfaces. In this paper, sodium nonylphenol polyoxyethylene ether sulfate (NPES) and sodium lauric acid ethanolamine sulfonate (HLDEA) were compounded to construct an efficient oil displacement system that simultaneously achieves wettability control of lipophilic surfaces and ultralow oil-water interfacial tension. The HLDEA + NPES system reduces the interfacial tension to 3.8 × 10^-3 mN·m^-1 and enhances surface wettability control, with an underwater oil contact angle of 157.2°. The compound system can remain stable at high temperatures (up to 110 °C) and high salinity (1 × 10⁵ mg·L^-1 NaCl and 7 × 10³ mg·L^-1 Ca²⁺). The oil recovery rate increases by 28.7% compared with water flooding and surpasses by 7.8% compared with a commercial ultralow interfacial tension system (10^-4 mN·m^-1). The synergistic effect of HLDEA and NPES in the oil/water interface increases the interfacial modulus and phase angle, thereby improving the stability of the interfacial film. The synergistic adsorption of HLDEA and NPES in the oil/water interface creates a denser adsorption layer, achieving enhanced wettability control. The HLDEA + NPES system balances the interactions from the oil-water and oil-solid interfaces, achieving a synergistic effect of oil film peeling and oil droplet migration, thereby significantly improving the recovery rate.