3 mN/m),low oil/water interfacial tension(minimum interfacial tension is 2.

In order to improve the ability of reducing oil-water interfacial tension of oil displacement agents and improve the oil recovery efficiency,the modified nano-SiO2-petroleum sulfonate super surfactant and sulfonate Gemini surfactant-petroleum sulfonate super surfactant were prepared based on the surface and interfacial activities of petroleum sulfonate.

The ability of the composite system for reducing the oil-water interfacial tension was measured by interfacial tensiometer TX-500.

The oil-water interfacial tension of each fraction was analyzed under different conditions.

The physicochemical properties of surfactin generated from a bacillus subtilis strain ZW-3,such as critical micella concentration value,the emulsification value,stability to salinity and temperature,ability to reduce the interfacial tension were measured in Daqing Oilfield.

Alkyl aryl sulfonate Ay-2 was synthesized and its interfacial tension behavior to crude oil of Daqig Oil Field and Dagang Oil Field was studied.

The interfacial tension at 40℃ between 3 model oils,crude,its resin and asphaltene solutions in toluene,and aqueous KYST-09A solution was determined by using droplet volume method,appeared to decrease fast with increasing KYST-09A concentration and became practically unchanged at KYST-09A concentration ～10 mg/L,particularly,in the case of crude solution in toluene.