Numerical Investigation of Hydro-Mechanical Processes During Hydraulic Stimulation at BedrettoLab

Hydraulic stimulation is a key technique in Enhanced Geothermal Systems (EGS) to enhance reservoir permeability, but it may also induce fault reactivation and seismicity. Understanding the coupled hydro-mechanical (HM) processes governing fluid pressure diffusion and rock deformation is therefore essential for reservoir optimization and seismic risk mitigation. In this context, validated and well-calibrated numerical models provide a cost-effective alternative to repeated field experiments, enabling the investigation of different stimulation scenarios.

In this study, we develop and validate a three-dimensional HM framework in COMSOL where the fractures and fault zone are described by an elstopaltsic constitutive model using data from the Bedretto Underground Laboratory (BedrettoLab). The model is applied to the hydraulic stimulation experiment conducted during VALTER Phase 1, where a discrete fault is explicitly represented. Model accuracy is evaluated by comparing simulated pressure and strain responses with observations from nearby monitoring wells, allowing us to assess the model’s ability to reproduce hydromechanical behaviour during injection.

To further investigate the experiment, we conduct a sensitivity analysis on key hydraulic and mechanical parameters, injection scenarios, and fault and fracture geometries. This analysis is used to explore the potential role of fracture networks surrounding the main fault and their influence on the system’s hydromechanical response.