Abstract: Coupled thermo-hydro-mechanical flows in complex fractured rock occur widely in unconventional and deep reservoir development scenarios. Coupled simulations of complex fracture networks will produce huge computational cost. Parallel computing technology is the effective method to achieve high-resolution simulations of complex discrete fractures. In this paper, massively parallel numerical simulation technology for thermo-hydro-mechanical coupling using general embedded discrete fracture model on unstructured grids is introduced. Firstly, a parallel solution of embedded discrete fracture model is achieved based on the domain decomposition method; and the way to decompose two independent matrix and fracture systems is introduced for unstructured grids. the existing embedded discrete fracture model by using two independent matrix and facture grid systems, and this approach significantly enhance the simulation ability of the EDFM for a complex 3D discrete fractures system. Secondly, for the thermo-hydro-mechanical coupling problem, the finite volume method is adopted to discretize compositional flow, heat transform and poro-mechanical equations uniformly, a parallel sequential implicit method is employed to solve the nonlinear coupling problem. Finally, this simulator is validated against two analytical model, and it is used for a multi-layer shale gas reservoir three-dimensional simulation and a deep high-temperature fractured reservoir simulation, and the parallel computational performance and scalability are analyzed at different parallel scales. The proposed methods can achieve high-resolution simulations of discrete fracture networks in practical engineering, and we obtain a great parallel performance and scalability at different scales, this simulator can be an efficient tool for the design and analysis of energy development in fractured rocks.

Key words: reservoir numerical simulation, embedded discrete fracture model, thermo-hydro-mechanical coupling, parallel computing, grid

摘要： 复杂裂缝系统热-流-固耦合流动广泛存在于非常规和深层油气藏开发过程中,由于裂缝系统热-流-固耦合数值模拟计算量巨大,并行计算技术是实现裂缝系统精细数值模拟的有效方法。对基于通用网格嵌入式离散裂缝模型的热-流-固耦合大规模并行数值模拟技术进行了研究。首先,基于区域分解方法,研发了嵌入式离散裂缝模型大规模并行求解技术,并且提出了在非结构网格中,基质与裂缝两套独立系统的连接关系分解方法。其次,针对多组分热-流-固耦合问题,使用有限体积法实现了组分流动、传热与力学控制方程的统一数值离散,使用顺序隐式牛顿方法对耦合非线性问题进行并行迭代求解。最后,通过与解析模型对比验证了数值方法的准确性,并且将数值模拟器应用于多层页岩气藏立体开发、深层高温裂缝性油藏注水开发数值模拟,并且在不同并行规模下对并行计算性能与可扩展性进行了分析。实现的并行数值模拟技术能够对实际工程中的三维离散裂缝系统进行大规模精细并行数值模拟,并且在不同的并行规模下都取得了良好的并行性能与可扩展性,能够成为裂缝性油气藏开发的有效设计与分析工具。

关键词: 油藏数值模拟, 嵌入式离散裂缝模型, 热-流-固耦合, 并行计算, 网格