异常高压气藏流固耦合的数值模拟

异常高压气藏具有比常规气藏更强的流固耦合效应，因而研究异常高压气藏流固耦合效应对于模拟气藏开采，指导气田生产具有十分重要的现实意义。为此，在气藏储层岩石应力、应变分析的基础上，结合修正的Terzaghi有效应力原理和岩石骨架本构关系，建立了异常高压气藏储层岩石骨架变形的数学模型；将固相平衡方程和流体流动方程组合，建立了异常高压气藏流固耦合模型。采用空间8节点等参元对圆柱形封闭地层进行了网格划分，基于Galerkin有限元法对流固耦合变形场、渗流场方程进行了空间域离散，并利用全隐式数值格式对半离散微分方程进行了时间域上的离散，建立了以位移和流体压力为未知变量的流固耦合有限元数值模型，并采用两场交替迭代的方法得到了控制方程在几何域上的耦合解。实例分析的结果表明，所建立的流固耦合模型比传统非耦合模型更能精确地描述异常高压气藏流体渗流与岩石变形的特征，与工程实际相符合，计算程序的精度高、可靠性强。

Numerical simulation of fluid-solid coupling of abnormally pressured gas reservoirs

Abnormally pressured gas reservoirs are of stronger fluid solid coupling effect than conventional gas reservoirs. Therefore, the study of such a subject is practically important for simulating the gas field exploitation and guiding the gas field production. To this end, a mathematical model was established for the rock matrix deformation of abnormally pressured gas reservoirs according to the analysis of gas reservoir rock stress and strain, modified Terzaghi effective stress principles, and rock matrix constitutive relation. Then, a fluid solid coupling model was set up through the combination of solid equilibrium equation with fluid flow equation. On this basis, spatial eight node isoparametric elements were used to mesh the cylindrical closed formation. With the Galerkin finite element method, the distortion field equation and fluid flow field equation of fluid solid coupling were scattered in space domain. Moreover, half discrete differential equation was scattered in time domain with fully implicit numerical format, as a result, the finite element numerical fluid solid coupling model was established, with displacement and fluid pressure as unknown variables, and the coupling solutions of control equation in geometrical domain were deduced with the alternating iterative method of two fields. The example analysis shows that the fluid solid coupling model is far more accurate than the traditional uncoupling model to describe the characteristics of seepage and rock deformation in abnormally pressured gas reservoirs, and its calculation programs are more precise and reliable.