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整体压裂会导致低渗透储集层发生固体应变,进而导致对气体渗流的影响。假设气藏开发生产过程为等温、单相气体渗流,并假设储集层为小变形弹性多孔介质,考虑岩石变形、地应力变化、人工裂缝、流体渗流与岩石应变耦合、储集层渗流与裂缝渗流耦合、非达西效应等因素,建立低渗透气藏整体压裂流固耦合渗流数学模型。首先推导出考虑固体应力应变的气藏整体压裂渗流模型控制方程;然后基于线弹性理论和有效应力概念,建立了孔隙含有气体的岩石的应力应变控制方程。由于这两组非线性控制方程互含应力、应变和压力项,因此用有限差分、块中心网格剖分方法,将方程组离散为主对角占优的七对角矩阵,采用隐式迭代方法求解,数值稳定性较好。通过示例分析,揭示了应力、应变、孔隙度和渗透率等参数的动态变化规律,而且模拟结果比其它模型更接近实际情况。图4参11(范学平摘)
Overall fracturing can lead to solid-state strains in the low-permeability reservoirs, which in turn can lead to gas seepage. Assuming that the gas reservoir development and production process is isothermal and single-phase gas seepage, and assuming that the reservoir is a small deformation elastic porous medium, considering deformation of rock, changes of ground stress, artificial fractures, fluid seepage and rock strain coupling, reservoir seepage and fractures Seepage coupling, non-Darcy effect and other factors to establish a whole fracturing fluid-solid coupling seepage mathematical model of low permeability gas reservoir. First, the governing equation of the overall fracturing seepage model of gas reservoir considering solid stress-strain is deduced. Based on the linear elasticity theory and the concept of effective stress, the stress-strain governing equations of the rock containing gas in the pores are established. Since the two sets of nonlinear governing equations contain stress, strain and pressure terms, the finite difference and block center meshes are used to disperse the system into the diagonal matrix with dominant diagonal dominance. Implicit iterations Method solving, numerical stability is better. Through the example analysis, the dynamic variation rules of stress, strain, porosity and permeability are revealed, and the simulation results are closer to the actual situation than other models. Figure 4 Senate 11 (Fan Xueping pick)