基于有限元与边界元耦合算法的页岩气藏体积压裂水平井产能计算方法

In the development of shale gas reservoirs, massive stimulated reservoir volume has been widely used, which greatly improves production. During the process of fracturing, a complex fractured mesh is generated, which is mainly manifested in the heterogeneity and the irregularity of fracturing region. Due to the limitations of characterization techniques and calculation methods, the heterogeneity and the irregularity are not considered in the current production capacity calculation. For the first time, the finite element and boundary element coupling algorithm is used to calculate the productivity of gas reservoir. It studies on flow mechanism of shale gas, characterizes the heterogeneity of fracturing region using triangular unstructured grid and permeability tensor, builds finite element equation of fracturing region based on Galerkin Method, constructs boundary element equation of non-fracturing region based on the Green function and the point source solution theory. It realizes effective characterization of the reservoir “global homogeneity and local heterogeneity”, and is efficient for the productivity calculation under arbitrary boundary condition. At the same time, the finite element and boundary element coupling algorithm is designed, and builds a capacity calculation method of stimulated reservoir volume horizontal well in shale gas reservoirs. The results reveal stimulation mechanism of stimulated reservoir volume, and It has a certain guiding significance to improve the development of shale gas reservoir.

大规模体积压裂技术已广泛应用于页岩气藏的开发，极大地提高了页岩气井产量。体积压裂过程中产生了复杂的裂缝网格，主要表现为压裂区域的非均质性与边界形状的不规则性。受表征技术和计算方法的限制，目前产能计算中未考虑压裂区非均质性和边界形状不规则性。申请人首次将有限元与边界元耦合算法运用于气藏工程产能计算，探究页岩气多尺度流动机理，引入三角形非结构网格和渗透率张量表征压裂区域非均质性，基于伽辽金法建立压裂区域有限元方程，基于格林函数及点源解理论建立非压裂区域边界元方程，实现储层“整体均质，局部非均质”特征有效表征与任意边界条件下产能模型高效计算，设计有限元与边界元耦合算法，建立页岩气藏体积压裂水平井产能计算方法。研究结果揭示体积压裂增产机理，对提升页岩气藏开发效果有一定指导意义。

大规模体积压裂技术已广泛应用于页岩气藏的开发，极大地提高了页岩气井产量。体积压裂过程中产生了复杂的裂缝网格，主要表现为压裂区域的非均质性与边界形状的不规则性。本研究主要针对页岩气流动机理、压裂区域非均质性表征方法、边界不规则性表征方法及页岩气藏体积压裂水平井产能计算方法开展研究。通过上述研究得到了如下成果：① 基于页岩气赋存特征和流动规律，建立了页岩气藏等效渗透率计算方法；② 设计了气井产能计算中压裂区域储层非均质性及区域形状不规则性表征方法，实现了页岩气藏体积压裂水平井产能模型的求解；③ 建立了页岩气体积压裂水平井产能计算方法。研究结果对揭示体积压裂增产机理及页岩气藏开发效果预测有一定指导意义。