Mechanical and microstructural properties of Gonghe granite for enhanced geothermal systems: Thermal effects and energy evolution

作者：Zhouqian Wu, Dongming Zhang, Yajin Liang, Shifeng He, Heping Xie, Minghui Li · 发表于：Journal of Rock Mechanics and Geotechnical Engineering · 年份：2025 · DOI：10.1016/j.jrmge.2025.06.016 · 被引用次数：6 · 研究领域：Rock Mechanics and Modeling、Geological and Geochemical Analysis、High-pressure geophysics and materials

Investigating the mechanical behavior and microstructural evolution of granite under high temperatures is crucial for optimizing fracturing strategies and ensuring reservoir sustainability in enhanced geothermal systems (EGS) at the Qiabuqia geothermal field, China. This study conducted triaxial compression tests on granite from the Qinghai Gonghe Basin under temperature from 25 °C to 300 °C, examining the effects of temperature and confining pressure on the mechanical properties and energy evolution of the granite. Additionally, X-ray diffraction (XRD) analysis and nanoindentation tests were employed to assess changes in micro-mechanical properties and mineral compositions. Furthermore, fracture mechanics principles, incorporating thermal stress effects, were utilized to calculate the initiation pressure of reservoirs at an engineering scale for geothermal development in the Qinghai Gonghe Basin. The results indicate that the compressive strength and elastic modulus of Gonghe granite increase with temperature up to 200 °C due to the enhancement of mineral mechanical properties and thermal densification, but significantly decrease at 300 °C due to thermal damage and fracture propagation. Energy analysis reveals that the granite undergoes a transition from brittle to ductile behavior under high-temperature conditions. The proportion of energy dissipation during deformation increases with temperature. The increased proportion of quartz, coupled with its high thermal expansion c...