Abstract:Based on the features of surfactant flooding, a mathematical model for surfactant flooding is established. The adsorption-retentlon, convection diffusion of surfactant and influence of concentration change upon relative permeability curve are included in the model. The novel description of adsorption quantity of surfaetant and relative permeability curve are presented, which enhance the coincidence between mathematical model and field practice, the relative errors of main development indexes arc within 6%. The model is applied to the numerical research of the surfactant flooding in the untabulated beds of Xingl-3 surfactant flooding pilot site of No. 4 Oil Production Company of Daqing Oilfield, the influences of surfaetant concentration, injection quantity, slug combination mode upon the development effect and economic benefit are quantitatively analyzed, the injection scheme is optimized as follows： surfaetant concentration is 0.5%, slug volume is 0.02 PV, slug combination mode is 2 slugs. After the implementation of scheme in oilfield, the cumulative increase of oil is 2186.0 t, up to nearly 30%. Key words:Surfactant, mathematical model, injection scheme, numerical simulation, recovery efficiency