关键词: low permeability reservoir, quaternary ammonium salt, betaine surfactant, interfacial tension, reducing injection pressure, enhancing oil recovery

Abstract: In view of the problems of high injection pressure and low water injection rate in water injection wells of low permeability reservoirs with high temperature and high salinity, two new surfactants were synthesized, including quaternary ammonium Gemini surfactant and betaine amphoteric surfactant. The composite surfactant system BYJ-1 was formed by mixing two kinds of surfactants. The minimum interfacial tension between BYJ-1 solution and the crude oil could reach 1.4×10-3mN/m. The temperature resistance was up to 140℃, and the salt resistance was up to 120g/L. For the low permeability core fully saturated with water phase, BYJ-1 could obviously reduce the starting pressure gradient of low permeability core. While for the core with residual oil, BAY-1 could obviously reduce the injection pressure and improve the oil recovery. Moreover, the field test showed that BAY-1 could obviously reduce the injection pressure of the water injection well, increase the injection volume, and increase the liquid production and oil production of the corresponding production well.

Key words: low permeability reservoir, quaternary ammonium salt, betaine surfactant, interfacial tension, reducing injection pressure, enhancing oil recovery