致密变形介质油藏五点面积井网水驱动态分析

Analysis of water flooding behavior in a five-spot well pattern in tight deformed reservoirs

致密变形介质油藏水驱渗流过程中会产生部分或全部不可逆形变,地层渗透率、孔隙度会发生不同程度降低,水驱渗流阻力大,难以形成有效的驱动压力系统,原油难以得到很好的动用,采收率低.以水驱油渗流模型入手,以介质变形理论为依托,利用叠加原理推导了考虑介质变形五点面积井网势函数、压力函数、流函数和平面速度函数解析公式,根据流函数得到井网流线.结合物质平衡理论,通过对平面速度函数积分得到无因次井网单元见水时间.基于不变流线假设,通过特征线方法求解水驱油渗流方程组得到平面等饱和度线运动方程.研究结果表明,介质变形系数对储层有效动用程度有重大影响,介质变形造成面积井网动用程度降低,介质变形系数越大,储层有效动用程度越低,采出程度越低.

A partial or complete irreversible deformation is generated in the development process of tight deformed reservoirs.Formation permeability and porosity will decrease with various degrees,the resistance to water flooding is large,and it is difficult to form an effective driving pressure system to exploit and develop the crude oil.As the result,the degree of the effective development is low.This paper takes full account of the characteristics of non-linear oil-water two-phase seepage in a low permeability reservoir.Deformed porous media,potential function,pressure function,stream function and velocity function analytical formulations are presented by considering of the influence of stress sensitivity through the superposition principle.According to the material balance theory,the breakthrough time of the dimensionless well pattern unit is derived through the integral of the velocity function.Moreover,according to the constant streamline hypothesis,a motion equation of the isosaturation surface is derived with a characteristic line method.The results show that by this new method,the stress sensitive coefficient has a significant impact on the effective development coefficient.The larger the media deformation factor is,the lower are the effective development coefficient and the oil recovery.