The Effect of Surfactants on Imbibition-Sensitive Factors of Low-Permeability Reservoirs

Interfacial tension and wettability are decisive factors for capillary force. Identifying the effect of surfactants on interfacial tension and wettability can be beneficial in improving the oil imbibition recovery rate in low permeability reservoirs. In this study, the effects of surfactants on the oil-water interfacial tension, surface wettability, capillary pressure and imbibition recovery were investigated through imbibition tests, spinning drop and dynamic contact angle methods, with 7 hydrophilic artificial cores with different permeability. Research results suggest that oil-water interfacial tension decreases significantly as the mass fraction of surfactant RS-1 increases, and then increases slightly before eventually becoming stable. The surfactant is highly capable in water wet surface wettability change, and can reduce the capillary pressure and improve the imbibition recovery. Results indicate that the surfactant is ostensibly capable of reducing the interfacial tension, especially with mixed surfactants which can achieve better performance than individual surfactants. Imbibition recovery is negatively correlated with the logarithm of capillary pressures and interfacial tension.