ABSTRACT: In Enhanced Geothermal Systems (EGS), geothermal energy extraction relies on the creation and maintenance of fractures to facilitate fluid circulation and heat transfer. Cold water injection induces significant thermal stress, causing fractures to open, propagate, and close, which in turn impacts fluid flow distribution and long-term energy recovery. This study employs a coupled fluid-solid-heat reservoir-fracture-well simulator to analyze these effects under varying gravity, stress gradients, and geothermal conditions. Simulation results indicate that thermal contraction from cold water injection leads to fracture growth, influencing both artificial and natural fracture networks. Thermo-poro-elastic effects, gravity, and stress gradients play key roles in fracture dynamics, affecting fracture conductivity, and overall system efficiency. Changes in fracture geometry over time alter flow distribution, potentially leading to uneven heat extraction and localized cooling. Understanding these complex interactions allows for the optimization of fluid injection and circulation strategies to enhance geothermal energy recovery. Properly managing thermally induced fracture behavior can improve heat extraction efficiency, maintain fracture connectivity, and extend the operational lifespan of EGS projects. By focusing on artificial fracture behavior under different mechanisms, this study provides insights into optimizing fracture design and operational strategies to achieve more efficient and sustainable geothermal energy extraction.
Hu et al. (Sun,) studied this question.
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