| Abstract |
Harnessing geothermal energy offers a clean and renewable resource, but field-scale modeling of Engineered Geothermal Systems (EGS) presents challenges due to the complex coupling of fluid flow, heat transfer, and geomechanics. These processes span scales from micro-level fracture interactions to macro-level reservoir behavior. Traditional numerical approaches, such as finite difference (FD), Discrete Fracture Network (DFN) modeling, and hybrid Finite Element Method (FEM) coupled with finite volume or FD simulators, often face limitations in addressing the intricate physics of EGS. Key challenges include capturing the multi-scale physical processes, representing discontinuities at fracture-matrix interfaces, and efficiently integrating multiple interacting phenomena. Additionally, modeling the dynamic propagation of fractures driven by evolving pressure and temperature remains a difficult task. This paper introduces an advanced phase-field modeling approach to overcome these limitations, which can naturally represent fracture initiation and growth without requiring pre-defined fracture geometries. The enriched Galerkin method is employed to discretize flow and energy equations, providing enhanced accuracy in capturing discontinuities around fractures. A fixed-stress split strategy is used to decouple the fluid flow and energy equations from rock mechanics and the phase-field equations, resulting in improved computational efficiency. The implementation within the open-source MOOSE framework enables simulations across scales. The proposed methodology is validated against analytical s and a 3D triaxial laboratory experiment that replicates pressure-induced fracture propagation. Furthermore, the approach is applied to field-scale EGS simulations in the Forge geothermal project, with validation through microseismic and pressure data, demonstrating the model's accuracy in representing real-world geothermal system behavior. This framework offers a pathway for more precise and efficient modeling of complex geothermal systems. |