基于混合方法的二维水力压裂数值模拟

水力压裂在页岩气开采中被广泛使用,采用数值方法研究压裂机理具有重要意义.基于连续-非连续单元法(CDEM) 和中心型有限体积法(FVM),提出解决水力压裂流固耦合问题的二维混合数值计算模型.该混合模型中,使用CDEM 求解应力场和裂缝扩展过程,使用FVM 求解裂隙渗流场.应力场裂缝扩展和渗流场均使用显式迭代求解, 并通过相互之间数据交换实现流固耦合.通过与KGD 理论模型进行对比, 验证数值模型的正确性.通过与颗粒离散元数值结果进行对比,验证数值模型的有效性.通过计算复杂缝网压裂模型,研究水力压裂机理,并说明该数值模型在水力压裂模拟中具有很好的前景. 

NUMERICAL SIMULATION OF HYDRAULIC FRACTURING BY A MIXED METHOD IN TWO DIMENSIONS

Hydraulic fracturing is widely used in exploitation of shale gas nowadays. It is of great significance to study the mechanism of fracturing process by numerical simulations. We present a mixed numerical model to solve hydraulic fracturing problems based on Continuous-Discontinuous Element Method (CDEM) and Finite Volume Method (FVM). In the mixed model, the CDEM is used for analysis of stress field and fracture propagation, and the FVM is used for analysis of pressure field in fracture. The three fields are all solved by explicit schemes and the coupling of them is implemented through data exchange. The model is verified against the classic KGD analytical solutions. Thereafter, it is validated by the results from a distinct element simulation. Finally, a hydraulic fracturing example related to complex fracture network is studied on the mechanism of fracturing process. The example shows bright future of the mixed numerical model for simulation and mechanism study of hydrauling fracturing.