Can Coupled Geomechanics Improve Forecasting in Enhanced Geothermal Systems?

Abstract

Thermo-hydraulic modeling of fluid flow and heat extraction in porous media is widely used in enhanced geothermal systems (EGS), often incorporating discrete fracture networks to represent complex fracture geometries. In these models, the elevated permeability near fractures is typically governed by aperture width – a key parameter for matching field observations. However, many existing approaches do not fully couple fracture opening and closure with mechanical responses to high-pressure fluid injection, potentially limiting their predictive accuracy. To address this, we focus on a single dominant fracture at the Utah FORGE site and develop a coupled thermo-hydro-mechanical (THM) model using a discontinuous Galerkin method integrated with a cohesive zone model to explicitly capture fracture deformation during injection. This formulation allows fracture aperture to evolve dynamically in response to thermal stresses and fluid pressure, enabling more realistic predictions of permeability evolution. By reducing the computational domain to a few hundred meters and focusing on a single fracture, we strike a balance between physical fidelity and computational feasibility. The model is further coupled with an optimization algorithm to calibrate key parameters against observed data. We compare the results with those from a purely thermo-hydraulic model using a prescribed aperture distribution – such as an elliptical profile with sigmoid decay – to evaluate whether geomechanical coupling improves predictive performance. The findings provide insights into the role of mechanical feedback in EGS performance and offer a valuable tool for the design and optimization of stimulate strategies.