The research progress in the alkali-free surfactant-polymer combination flooding technique

Alkali-free surfactant-polymer SP flooding can avoid scaling, strong emulsification and corrosion caused by alkali, thus reduce the investment and operating cost. It is a new chemical flooding technology for Enhanced Oil Recovery (EOR) with a promising application prospect. The main problems of SP flooding are as follows: shortage of industrialized surfactant product with high performance, weak theoretical research on oil displacing mechanisms and main influencing factors, unsound evaluation methods, lack of pilot tests, and high technical risk. The main factors that affect the oil displacement efficiency of SP flooding are displacing fluid viscosity, interfacial tension, and emulsification strength of SP system. The high viscosity of SP flooding formula system is an important guarantee of EOR process. The lower the interfacial tension, the higher the oil recovery degree is. The emulsify ability of SP system can significantly affect efficiency of oil displacing. SP flooding process has obtained certain effects in pilot tests but there are still some problems. The formula adaptability and quality stability of surfactant product should be improved, the injection program should be optimized, and the field monitoring and process tracking and regulation should be strengthened.