Numerical Simulation of HDR Geothermal Energy Reservoirs: A Thermo-Hydro-Mechanical Model

This paper investigates thermal energy extraction from hot dry rock (HDR) geothermal reservoirs using a three-dimensional (3D) coupled model of thermo-hydro-mechanical (THM) processes. The model is implemented in the COMSOL Multiphysics Finite Element (FE) solver and its reliability is confirmed by conducting a validation study using the first HDR field measurements from Fenton Hill, New Mexico. After confirming the reliability of the model, a comprehensive simulation study is conducted on six different configurations of HDR geothermal reservoirs varying by wellbore alignment and reservoir growth direction, to determine the best configuration for optimal thermal energy production. The results show that thermal energy extraction is affected by the following factors: pore pressure, wellbore alignment, in-situ stress, aperture changes, and reservoir growth direction. The simulation highlights the influence of coupled THM processes in evaluating the long-term behaviour of HDR geothermal reservoirs. Thus, the study will guide geologists, engineers and decision-makers in producing the optimal designs for these systems.