摘要：Composite thermal recovery technology for heavy o il reservoirs has been studied at home and abroad. Surfactants can increase crude o il recovery during thermal recovery and flu id salinity surfactants have significant effects on o il displacement. In this paper, interfacial tension measurement and contact angle measurement experiments are used to study the effect of salinity on the interfacial tension and reservoir wettability. The results show that salin ity has a significant effect on the w ettability of oil- wet sandstone surface. As the fluid salinity increases, the o il w ettability increases. The influence of Ca2+is more obvious than that of Na+. Fluid salinity changes the charge distribution between rock-brine-crude oil, which affects surface forces and leads to changes in wettability. In addition, as salinity increases, the effect of surfactants to reduce the interfacial tension of o il and water decreases first and then increases, indicating that there is an optimal salt content. The core flooding experiment investigated the displacement effect of surfactants under different salt contents. The results show that Ca2+ can stabilize the o il film , enhance the lipophilicity, and reduce the recovery factor significantly. Reducing the NaCl content can not only improve the oil-water interfacial tension, but also improve the rock surface w ettability and increase the o il recovery. When the salt content drops to 0.5%, the effect on o il recovery is no longer significant.
