Alkaline-surfactant-polymer(ASP)flooding using sodium hydroxide as the alkali component to enhance oil recovery in Daqing Oilfield,northeast China has been successful,but there are new problems in the treatment of produced crude.The alkali added forms stable water-in-crude oil emulsion,hence de-emulsification process is necessary to separate oil and water.The problems in enhanced oil recovery with ASP flooding were investigated in laboratory by using fractions of Daqing crude oil.The oil was separated into aliphatics,aromatics,resin and asphaltene fractions.These fractions were then mixed with an additive-free jet fuel to form model oils.The interfacial properties,such as interfacial tension and interfacial pressure of the systems were also measured,which together with the molecular parameters of the fractions were all used to investigate the problems in the enhanced oil recovery. In our work,it was found that sodium hydroxide solution reacts with the acidic hydrogen in the fractions of crude oil and forms soap-like interfacially active components,which accumulate at the crude oil-water interface. Alkaline-surfactant-polymer (ASP) flooding using sodium hydroxide as the alkali component to enhance oil recovery in Daqing Oilfield, northeast China has been successful, but there are new problems in the treatment of produced crude. The alkali added forms stable water-in -crude oil emulsion, hence de-emulsification process is necessary to separate oil and water. The problems in enhanced oil recovery with ASP flooding were investigated in laboratory by using fractions of Daqing crude oil. The oil was separated into aliphatics, aromatics, resin and asphaltene fractions. These fractions were then mixed with an additive-free jet fuel to form model oils. interfacial tension, interfacial pressure of the systems were also measured, which together with the molecular parameters of the fractions were all used to investigate the problems in the enhanced oil recovery. In our work, it was found that sodium hydroxide solution reacts with the acidic hydrogen in the fractions o f crude oil and forms soap-like interfacially active components, which accumulate at the crude oil-water interface.