Abstract Simulation of thermal hydraulic-mechanical (THM) coupling process plays an important role in exploiting the hot dry rock (HDR) resources by enhanced geothermal systems (EGS). At present, the simulations are mostly performed by using the traditional finite element method (FEM) with very dense grids. Because of the considerable size differences between the fractures and EGS, a large number of unstructured grids should be adopted, leading to a significant computational burden. To address this challenge, the embedded discrete fracture model (EDFM) and the extended finite element method (XFEM) are combined in this paper. By doing this, the grid number can be dramatically reduced, which improves the computational efficiency while maintaining relatively high accuracy. The proposed model is verified by comparing it with two typical analytic solutions and COMSOL. Moreover, the new model is applied to analyze the pressure, temperature and displacement evolutions in a hypothetical EGS. The influences of some key variables on thermal extraction performance are also investigated.

中文翻译：

---

基于EDFM和XFEM框架的EGS热-水-机耦合过程建模研究

摘要 热力水力-机械（THM）耦合过程模拟在增强型地热系统（EGS）开发干热岩（HDR）资源中具有重要作用。目前，模拟大多使用具有非常密集网格的传统有限元方法（FEM）进行。由于裂缝和EGS之间存在相当大的尺寸差异，应采用大量非结构化网格，从而导致显着的计算负担。为了应对这一挑战，本文结合了嵌入式离散断裂模型 (EDFM) 和扩展有限元方法 (XFEM)。通过这样做，可以显着减少网格数，从而提高计算效率，同时保持相对较高的精度。通过将其与两个典型的解析解和 COMSOL 进行比较，验证了所提出的模型。此外，新模型还用于分析假设 EGS 中的压力、温度和位移演变。还研究了一些关键变量对热提取性能的影响。