Abstract: The harm of alkali becomes more and more obvious with the progress of the research on the ASP flooding technology for EOR. This paper presents the home-made petroleum sulfonate NPS-2 as a surfactant, by which investigates the effects of NaCl and petroleum sulfonates of different concentrations on the oil-water interfacial tension in area of No.4 oil production plant of Daqing Oilfield Company Ltd., determines the formulation for non-alkali binary flood system and evaluates its applicable universality and displacement effectiveness. The results show that this binary formulation system (C_NaCl=0.6%~1.2%, C_NPS-2=0.1%~0.3%, C_HPAM=0.12%) may allow the oilwater interfacial tension to be greatly decreased by order of 10^-3mN/m to 10^-4mN/m, hence avoiding the damages of alkali on oil-bearing strata and oil production equipments.

Key words: tertiary recovery, EOR, petroleum sulfonate, polymer, alkali, system