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| Shear seepage test of hot dry rock fractures and numerical evaluation of thermal performance in the enhanced geothermal system |
| WANG Chiyu1, WANG Tongbiao2, XIE Yachen3, LIAO Jianxing1, 2*, ZHOU Qing1 |
(1. College of Civil Engineering, Guizhou University, Guiyang, Guizhou 550025, China; 2. Guizhou Coal Mine Design and Research Institute Co., Ltd., Guiyang, Guizhou 550025, China; 3. College of Water Resources and Hydropower, Sichuan University,
Chengdu, Sichuan 610065, China) |
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Abstract Geothermal energy, a renewable resource with immense potential, has garnered significant attention. In deep geothermal reservoirs, artificially stimulated fracture networks serve as critical pathways for heat extraction. Consequently, the permeability and spatial distribution of these fractures directly impact heat extraction efficiency. This study conducted shear-seepage experiments on a single rough granite fracture under varying confining pressures, shear displacements, and fracture roughnesses. A nonlinear relationship between permeability and the aforementioned three factors was established based on the experimental results. This relationship was then integrated into the THM coupled framework TOUGH2MP-FLAC3D to assess the long-term performance of Enhanced Geothermal Systems (EGS) under varying fracture networks, fracture densities, and horizontal stress ratio conditions. The findings reveal that fracture permeability exhibits an exponential negative correlation with confining pressure, a logarithmic positive correlation with shear displacement, and a quadratic correlation with fracture roughness. Increased fracture density significantly enhances thermal performance; as fracture densities increase from 0.1 to 0.25, the thermal breakthrough time extends by up to 6.4 years, the EGS lifespan increases by up to 13 years, and total heat production rises by approximately 22.5%. Horizontal stress anisotropy negatively affects thermal performance, while higher fracture density effectively mitigates the reduction in heat extraction caused by stress anisotropy. This work provides a theoretical foundation for hydraulic fracturing during the stimulation of hot dry rock reservoirs.
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2026, Vol. 45 
