The surfactant assisted steam flooding efficiency was systematically investigated by means of laboratory experiments and numerical simulation in light of the specific reservoir conditions of Shengli oilfield.Some property parameters of high-temperature surfactant(WT) such as interfacial tension,temperature resistance and viscosity reducing property were determined.Experiment results showed that the minimum dynamic interfacial tension between WT solution and oil was of 10-2 mN/m.And the temperature resistance researched to 150℃.The half-life was over 15 d.When the mass ratio of oil to water was of 8∶ 2 and 7∶ 3,the viscosity reducing rate was higher than 86% and 95%,respectively.The ultimate recovery of surfactant assisted steam flooding was of 74.32%,which improved by 12.11% comparing with steam flooding.Based on displacement experiments,the injection parameters of surfactant for the typical well group in Zhongerbei Ng5 of Gudao oilfield were optimized by numerical simulation technique.The optimum injection project was obtained as follows: alternative injection,0.5% surfactant dosage and 0.3 PV injection volume.The increasing oil recovery of the optimum plan predicted was of 3.58%.The expression of economic minimum oil increment was derived by dynamic economic evaluation.Based on this,a method for studying economic and technical boundary values of surfactant assisted steam flooding was built.Effective thickness and oil viscosity economic and technical boundary values of the typical well group were studied.