Numerical simulation of thermo-hydro-mechanical coupling effect in mining fault-mode hot dry rock geothermal energy

• Published in: Renewable energy Vol. 139; pp. 120 - 135
• Main Authors: Wei, Xin, Feng, Zi-jun, Zhao, Yang-sheng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2019
• Subjects: Fluid flow in fault; Hot dry rock geothermal energy; Mining lifespan; Thermo-hydro-mechanical coupling model; Hot dry rock geothermal energy; Thermo-hydro-mechanical coupling model; Fluid flow in fault; Mining lifespan
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2019.02.070

Hot dry rock geothermal energy is a type of renewable energy with great development prospects in deep strata. However, it is quite difficult to construct an artificial reservoir. In this paper, deep large-dip-angle fault zone in the Yangbajing geothermal field in Tibet of China is used as a natural artificial reservoir, and a set of hot dry rock heat extraction schemes for such fault modes is proposed. A three-dimensional thermo-hydro-mechanical coupling model is established for the scheme to study the distributions of temperature, stress and seepage during the process of mining fault-mode hot dry rock geothermal energy. The temperature of #1 production well remains 445 °C after 22-year operation and it decreases from 445 °C to less than 200 °C after 15-year operation in #2 production well. The initial vertical stress near the injection well is 199 MPa, which decreases to 193 MPa after 1 year and remains unchanged. The specific water flow in the fault zone between the wells increases negatively and exponentially with the extraction time. The seepage resistance of the fault rock mass gradually decreases. The total effective heat production is 13130 MWa after 22-year operation. •Fault zone can be used to easily construct artificial reservoir in EGS.•Seepage resistance of fault rock mass gradually decreases with mining time.•Extracted water temperature exponentially decreases with mining time.•A geothermal power plant with capacity of 500 MW has more than 25-year lifespan.