Fluid Distribution And Seepage Characteristics Of Air Foam Flooding In Low Permeability Oil Reservoirs

Air foam flooding has many advantages of gas flooding and surfactant flooding which can selectively block the dominant channels and greatly improve sweep efficiency,so air foam flooding is especially applicable for low permeability oil reservoirs.However,the result of the field application is not expected because of the great difference between the indoor conditions and the field.Therefore,study the foam fluid distribution and seepage characteristics under the reservoir condition,reveal the seepage law of the different driving cycles,are the keys to improve the application effect of low permeability reservoir.In this paper,the mechanism of foam generation in porous media is re-recognized,and the distribution characteristics of foam in the actual reservoir conditions are evaluated based on the tree-like model.According to the influence of foam on gas liquid flowing,a prediction model of foam flooding resistance factor is established.The relative permeability retardation phenomenon in the air foam flooding of alternative injection was revealed for the first time based on the prediction model of gas liquid relative permeability of STARS foam flooding.On this basis,according to the characteristics of the low permeability oil field parameters,carry out the core flooding experiment and numerical model,analyze the influence of heterogeneity and different distribution of oil saturation of air foam flooding,which are useful to improve the air foam flooding seepage theory and the application effect of air foam flooding in low permeability reservoir.The results show that foam will occur when the pore throat structure and water saturation reach the conditions.Under the condition of the reservoir,the foam will be mainly distributed around the gas liquid front because of the long cycles.After many rounds of alternating,the trapped gas will accumulate,then the gas phase relative permeability of same gas saturation decreased significantly,showing obvious gas phase permeability hysteresis.However,the relative permeability of the liquid will decrease slightly due to the influence of the foam on the liquid phase saturation.The air foam flooding can not only improve the oil displacement efficiency,but also reach the area which water flooding can not.For low permeability reservoirs with high permeability ratio,the existence of foam can improve the flowing of the dominant direction and improve the overall development effect.