272-2 Applications of Slip and Dilation Tendency Analysis for Geothermal Energy Extraction

Session: Faults, Fractures, and Geomechanics for the Energy Transition (Posters)

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Geothermal energy represents an important and largely untapped resource for electricity and clean energy generation in the United States and abroad. Individual geothermal wells can cost upwards of $20 million depending on depth, yet many geothermal wells drilled worldwide have been economically unsuccessful. For geothermal energy economic viability, two fundamental subsurface components are required: heat and permeable flow pathways. Faults and fractures are essential fluid flow pathways in many geothermal fields, but their permeability is highly dependent on subsurface stress state. Understanding subsurface stress states and how they evolve during reservoir stimulation (“enhanced geothermal”) and geothermal production with associated reservoir cooling is critical for site selection, well planning, and economic feasibility of geothermal projects. Changes in fluid pressure and heat extraction from geothermal fields are key drivers of temporal stress state evolution that can modify the permeability of faults and fractures in the subsurface.

This study employs finite-element geomechanical modeling and resolved stress analysis to explicitly understand key stress drivers and resulting spatial and temporal stress state variations in geothermal reservoirs. 2D and 3D geomechanical models are used to characterize the spatial and temporal evolution of the stress state in the subsurface and simulations use geologically realistic subsurface configurations with different lithologic domains, pre-existing discontinuities, and initial conditions. Imposed temperature and pore pressure changes are used as the primary loads. Slip and dilation tendency analyses provide a rigorous means for assessing the fluid flow potential of discontinuities under applied and dynamic stress conditions.

Geomechanical simulations showed that: (1) initial stress conditions and mechanical and thermal rock properties are important controls on the spatial/temporal evolution of subsurface stresses in response to production and injection; (2) stress state perturbations (changes in orientation and magnitude of stresses) are likely to extend well beyond the regions where the primary temperature and pore pressure changes take place due to production and injection; and (3) slip and dilation tendency analyses track changes in fracture response to production-related stress evolution, and provide a means to reduce risk by identifying evolving flow paths. Tracking the evolution of slip and dilation tendency of known and potential geologic fluid conduits (faults and fractures) during the geothermal-driven stress evolution provides a means to better understand both the short- and long-term viability of geothermal extraction projects.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7116

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