特低渗透油藏动态毛管压力对水驱油效果影响分析

特低渗透油藏油水两相渗流过程中毛管力的动态效应是影响两相渗流机理及水驱油效果的重要因素,掌握其规律有助于提高这一特殊油藏的水驱开发效果。分析了特低渗透油藏油水两相渗流中毛管力的动态效应以及动态毛管力的影响因素,定量研究了动态毛管力对多孔介质油水两相渗流的影响,建立了特低渗透油藏一维水驱油模型和渗流微分方程;并进行了求解。研究了动态毛管力、注水强度、井距等因素对特低渗透油藏水驱油效果的影响。研究结果表明:动态毛管力效应对特低渗油藏的水驱效果影响非常明显,动态毛管力越大,水驱油效果越差;存在一个最佳注入量,在最佳注入量下动态毛管力的影响作用最小,水驱油效果最好;对于特低渗透油藏若井距过大,水驱油效果变差。

Investigation of the Effect of Dynamic Capillary Pressure on Water flooding in Extra Low Permeability Reservoirs

The dynamic capillary pressure is one of the important factors affecting the two phase percolation mechanism of water-flooding in extra low permeability reservoir. It is crucial to understand the effect of dynamic capillary pressure on oil displacement process in order to improve the water-flooding effectiveness. In this paper the dynamic capillary pressure effect was investigated quantitatively and a linear percolation flow model was built, in which the dynamic capillary pressure is considered. The effects of dynamic capillary pressure, water injection rate and well spacing on the water-flooding effectiveness were analyzed. The results show that the dynamic capillary pressure has a significant influence on the oil displacement effectiveness. The bigger the dynamic capillary pressure, the more adverse water-flooding effectiveness is obtained. The water injection rate will influence the change of fluid saturation in the reservoir, which leads to the different dynamic capillary pressure effect. There is an optimum water injection rate which causes the minimum dynamic capillary pressure and percolation resistance. It is not recommended to select larger well spacing, which can cause the adverse dynamic capillary pressure and water-flooding effectiveness in extra low permeability reservoir.