A Cutting-Edge Thermal Model for Enhanced Geothermal System (EGS) with Complex Fracture Geometry

Enhanced Geothermal System (EGS) has gained great attention since it delivers a geographically disperse, carbon-free energy without the environmental impact. The thermal fracture network also significantly contributes to the energy extraction of EGS. The objective of our EGS model is to evaluate the temperature behavior of the complex fracture network and producing a temperature profile in a natural fractured EGS system. Our model will improve the economical evaluation of the EGS system. In this work, we developed a comprehensive numerical model for EGS. Our model includes the reservoir and wellbore model. The flow and thermal model are fully coupled. A thermal embedded discrete fracture model (Thermal EDFM) is developed to handle the thermal modeling of complex fracture networks. The thermal non-neighbor connections enable us to efficiently simulate the temperature behavior within a massive complex fracture network. Subsequently, we developed a thermal wellbore model to accurately evaluate the heat loss in the injector and producer. Our EGS analysis with our model provides a high-resolution temperature evaluation since we consider the true flow and temperature behavior in each fracture without any upscaling. The thermal reservoir and wellbore model deliver an accurate heat loss estimation during injecting, flowing through the fracture network, and producing, which benefits the economical evaluation and decision-making process. Our EGS model has been applied to Utah's enhanced geothermal system for economically evaluate the hot dry rock reservoir and optimize the operation. Although numerous simulators are developed for EGS, relatively few existing models can handle the full-physics such as complex fracture geometry and multiphase flow. Our model is more rigorous than the prior models to simulate the field geothermal reservoir.