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Modeling Microseismicity in Enhanced Geothermal Systems: Impacts of Injection Parameters at Utah FORGE
Nicolas CARDENAS ACEVEDO, Xu SI, Sheng DAI, Zhigang PENG, Jesse WILLIAMS, Wencheng JIN
[Texas A&M University, Department of Petroleum Engineering, USA]
Enhanced Geothermal Systems (EGS) rely on hydraulic stimulation to increase permeability in low-permeability rock formations. However, this process often induces microseismicity due to the initiation and propagation of new fractures, as well as slip along pre-existing fractures. Understanding the mechanisms and controlling factors of induced seismicity is essential for optimizing stimulation strategies while ensuring operational safety and maintaining public confidence. The Utah Frontier Observatory for Research in Geothermal Energy (FORGE) provides a unique opportunity for investigating these relationships, offering high-quality datasets with well-characterized subsurface conditions. This study aims to evaluate the influence of key injection parameters, including the rate, duration, and viscosity of injected fluids, on the evolution of microseismicity during and post-stimulation. We develop a series of high-fidelity, hydro-mechanical numerical simulations using XSite, a lattice-based simulator capable of modeling tensile and shear failures in rockmass with complex fracture networks. The simulation domain replicates the 2024 stimulation performed at well 16A(78)-32 at the FORGE site. Discrete Fracture Networks (DFNs) were constructed based on site data, with variations in hydromechanical properties such as the aperture, normal stiffness, and friction coefficient of fractures, informed by laboratory and borehole observations. Each model was calibrated by comparing wellhead pressures and Gutenberg-Richter magnitude-frequency distributions (MFDs) between in situ measurements and numerical predictions. The calibrated models were then employed to quantify the effects of injection rate, total injection volume, and fluid viscosity on the maximum magnitude and MFD of induced seismicity during and after injection. Further analysis will focus on the generation mechanisms of post-injection seismicity and the stress shadowing effects between closely located fracture clusters.
Topic: FORGE