水压致裂过程的弹塑性细胞自动机模拟

Modeling Hydraulic Failure Process Using Elasto-Plastic Cellular Automaton

利用自行研发的弹塑性细胞自动机模型和模拟系统,建立了非均质岩石水压致裂过程的细胞自动机模拟方法.该方法能够反映流体在水力梯度作用下进入新生微裂隙、形成新的流体渗流边界而对该边界产生张拉效应,并引起微裂隙的进一步扩展、贯通,最终形成宏观裂纹的过程,可以方便地进行水压致裂过程中边界条件和水力参数的动态更新.同时,研究了不同均质度和井筒内径对水压致裂行为的影响.结果表明,随着井筒内径增加,极限水压力降低,而破裂模式基本相似,模拟结果与典型实验现象吻合较好.

A self-developed numerical tool,i.e.an elasto-plastic cellular automaton（EPCA） was used to simulate the hydraulic fracturing process of rocks.The modeling method of hydraulic fracturing process of heterogeneous rocks with cellular automaton was developed.With the increase of fluid load,fluid will go into the new cracks.The new fluid seepage boundaries will be formed and the tensile stress induced by fluid will be applied on the crack boundaries.In this process,the mechanical properties and boundary conditions will be updated dynamically.The cellular automaton,which is based on the localization theory,makes this operation more conveniently.With this method,the failure process of wellbore rock specimen under hydraulic pressure was simulated,by considering different heterogeneity and different inner radius of the wellbore.It is concluded that,in hydraulic fracturing process,the critical fluid pressure,crack propagation and final failure patterns etc.are greatly influenced by the heterogeneity of the rock,the boundary geometry etc.