【作者】 张旭东； 黄薇； 侯丙昌； 孙峰；

【Author】 Zhang Xudong;Huang Wei;Hou Bingchang;Sun Feng;College of Pipeline and Civil Engineering in China University of Petroleum (East China);

【机构】 中国石油大学(华东)储运与建筑工程学院；

【摘要】 裂缝形态数值模拟是研究材料断裂特征的重要手段。传统裂缝扩展的有限元方法由于应变软化后方程椭圆度的降低,存在网格依赖性问题。为解决裂缝扩展模拟过程中的网格尺寸效应,进一步在流固耦合渗流方程中引入渗透率与非局部化损伤变量的耦合关系,建立了水力压裂过程中裂缝扩展的非局部化有限元模拟方法。首先将模拟结果与"L"型脆性材料实验数据对比并进行网格敏感性分析,验证了其有效性,并且其计算准确性更高,损伤区域过渡更缓和。而后通过开展射孔角对裂缝扩展轨迹影响分析,研究了模型针对流固耦合裂缝扩展的可行性。结果表明,模拟的裂缝形态与实验结果吻合,利用非局部损伤本构的裂缝扩展模型能有效克服应变局部化问题,且裂缝扩展过程具有缝宽均匀、能有效避免裂缝前缘发散等优点。更多还原

【Abstract】 Numerical simulation of crack morphology is an important means to study the fracture characteristics of materials. The traditional finite element method of crack propagation has the problem of grid dependence due to the reduction of the ellipticity of the equation after strain softening. In order to solve the effect of mesh size in the process of fracture propagation simulation, the coupling relationship between permeability and non-localized damage variables is further introduced into the hydraulic-mechanical coupling seepage equation, and a non-localized finite element simulation method for fracture propagation during hydraulic fracturing is established. Firstly, the simulation results are compared with the experimental data of "L" type brittle materials, and the grid sensitivity analysis is carried out to verify its effectiveness, its calculation accuracy is higher, and the transition of the damaged area is more moderate. Then, by analyzing the influence of perforation angle on fracture propagation trajectory, the feasibility of the model for hydraulic-mechanical coupling fracture propagation is studied. The results show that the simulated crack morphology is consistent with the experimental results. The crack propagation model using the non-local damage constitutive can effectively overcome the strain localization problem, and the crack propagation process has the advantages of uniform crack width and can effectively avoid the divergence of the crack front.更多还原