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区别于常规气藏,页岩气藏渗流主要受解吸、扩散、窜流和常规达西流动控制,机理复杂。考虑到基质和裂缝系统之间存在的压力差,在将气藏看成是双孔单渗介质的基础上,新增加了一个扩散以外的窜流流动,通过引入2个新的参数分别表征扩散和窜流2个因素的影响,建立了页岩气藏含有多条横向裂缝的压裂水平井的渗流数学模型。在此基础上,基于源函数理论,采用镜像反应和叠加原理,得到了地层中任意一点的压力表达式,通过Laplace变换和Stehfest数值反演得到水平井井底压力解,绘制了不同条件下的压力动态曲线,并与目前存在的渗流数学模型进行了对比,为页岩气藏的试井分析和不稳态产能评价提供了理论依据。
Differing from the conventional gas reservoirs, the seepage of shale gas reservoirs is mainly controlled by desorption, diffusion, channeling and conventional Darcy flow control with complicated mechanism. Considering the pressure difference existing between the matrix and the fracture system, a new flow of channeling flow beyond the diffusion was added based on the gas reservoir as a double-pore single-permeable medium. Two new parameters were used to characterize the diffusion And channeling flow, the seepage mathematical model of fractured horizontal well with multiple lateral fractures in shale gas reservoir is established. On this basis, based on the source function theory, the pressure expression at any point in the formation is obtained by using the mirror reaction and superposition principle. The horizontal well bottom pressure solution is obtained by Laplace transform and Stehfest numerical inversion. Under different conditions Pressure dynamic curves are compared with existing mathematic models of percolation to provide a theoretical basis for well test analysis and evaluation of unsteady productivity of shale gas reservoirs.