The Hot Dry Rock(HDR)is considered as a clean and renewable energy,poised to significantly contribute to the global energy decarbonization agenda.Many HDR projects worldwide have accumulated valuable experience in eff...The Hot Dry Rock(HDR)is considered as a clean and renewable energy,poised to significantly contribute to the global energy decarbonization agenda.Many HDR projects worldwide have accumulated valuable experience in efficient drilling and completion,reservoir construction,and fracture simulation.In 2019,China Geological Survey(CGS)initiated a demonstration project of HDR exploration and production in the Gonghe Basin,aiming to overcome the setbacks faced by HDR projects.Over the ensuing four years,the Gonghe HDR project achieved the first power generation in 2021,followed by the second power generation test in 2022.After establishing the primary well group in the initial phase,two directional wells and one branch well were drilled.Noteworthy progress was made in successfully constructing the targeted reservoir,realizing inter-well connectivity,power generation and grid connection,implementing of the real-time micro-seismic monitoring.A closed-loop technical validation of the HDR exploration and production was completed.However,many technical challenges remain in the process of HDR industrialization,such as reservoir fracture network characterization,efficient drilling and completion,multiple fracturing treatment,continuous injection and production,as well as mitigation of induced seismicity and numerical simulation technology.展开更多
In the enhanced geothermal system(EGS),the injected fluid will induce shear sliding of rock fractures(i.e.,hydroshearing),which consequently,would increase the fracture aperture and improve the heat transfer efficienc...In the enhanced geothermal system(EGS),the injected fluid will induce shear sliding of rock fractures(i.e.,hydroshearing),which consequently,would increase the fracture aperture and improve the heat transfer efficiency of the geothermal reservoir.In this study,theoretical analysis,experimental research and numerical simulation were performed to uncover the permeability and heat transfer enhancement mechanism of the Hot-Dry-Rock(HDR)mass under the impact of shearing.By conducting the direct shear test with the fractured rock samples,the evolution process of fracture aperture during the shearing tests was observed,during which process,cubic law was adopted to depict the rock fracture permeability.To investigate the seepage characteristics and temperature distribution of the fractured HDR under the influence of shearing,a simulation study of shear-seepage-heat transfer in a fractured rock mass has been conducted to validate the observed shear-induced fracture dilation during the direct shear test.The results demonstrate that(1)the hydroshearing increases the dilation of granite fracture and enhances the permeability of the HDR rock mass,while the temperature around the HDR fracture will reduce.(2)Fracture roughness is of vital importance to enhance the permeability during the shearing tests.To be more specific,a rougher fracture always implies a higher permeability and a greater heat extraction efficiency.(3)The shear induced heat extracting efficiency is dominated by the increased fluid flux in the earlier period of the EGS reservoir,and this efficiency is controlled by the outlet water temperature since the fluid flux becomes stable after the shearing test.Therefore,balancing the hydroshearing enhanced heat extraction efficiency and EGS reservoir lifespan would be significant to the sustainable development and utilization of geothermal energy.展开更多
基金Funded by the“Investigation and Evaluation of the Hot Dry Rock Resources in the Guide-Dalianhai Area of the Gonghe Basin,Qinghai”(DD20211336,DD20211337,DD20211338)“Hot Dry Rock Resources Exploration and Production Demonstration Project”(DD20230018)of the China Geological Survey。
文摘The Hot Dry Rock(HDR)is considered as a clean and renewable energy,poised to significantly contribute to the global energy decarbonization agenda.Many HDR projects worldwide have accumulated valuable experience in efficient drilling and completion,reservoir construction,and fracture simulation.In 2019,China Geological Survey(CGS)initiated a demonstration project of HDR exploration and production in the Gonghe Basin,aiming to overcome the setbacks faced by HDR projects.Over the ensuing four years,the Gonghe HDR project achieved the first power generation in 2021,followed by the second power generation test in 2022.After establishing the primary well group in the initial phase,two directional wells and one branch well were drilled.Noteworthy progress was made in successfully constructing the targeted reservoir,realizing inter-well connectivity,power generation and grid connection,implementing of the real-time micro-seismic monitoring.A closed-loop technical validation of the HDR exploration and production was completed.However,many technical challenges remain in the process of HDR industrialization,such as reservoir fracture network characterization,efficient drilling and completion,multiple fracturing treatment,continuous injection and production,as well as mitigation of induced seismicity and numerical simulation technology.
基金supported by the Fundamental Research Funds for the Central Universities(2020XJNY03)the YueQi Distinguished Scholar Project of China University of Mining&Technology,Beijing。
文摘In the enhanced geothermal system(EGS),the injected fluid will induce shear sliding of rock fractures(i.e.,hydroshearing),which consequently,would increase the fracture aperture and improve the heat transfer efficiency of the geothermal reservoir.In this study,theoretical analysis,experimental research and numerical simulation were performed to uncover the permeability and heat transfer enhancement mechanism of the Hot-Dry-Rock(HDR)mass under the impact of shearing.By conducting the direct shear test with the fractured rock samples,the evolution process of fracture aperture during the shearing tests was observed,during which process,cubic law was adopted to depict the rock fracture permeability.To investigate the seepage characteristics and temperature distribution of the fractured HDR under the influence of shearing,a simulation study of shear-seepage-heat transfer in a fractured rock mass has been conducted to validate the observed shear-induced fracture dilation during the direct shear test.The results demonstrate that(1)the hydroshearing increases the dilation of granite fracture and enhances the permeability of the HDR rock mass,while the temperature around the HDR fracture will reduce.(2)Fracture roughness is of vital importance to enhance the permeability during the shearing tests.To be more specific,a rougher fracture always implies a higher permeability and a greater heat extraction efficiency.(3)The shear induced heat extracting efficiency is dominated by the increased fluid flux in the earlier period of the EGS reservoir,and this efficiency is controlled by the outlet water temperature since the fluid flux becomes stable after the shearing test.Therefore,balancing the hydroshearing enhanced heat extraction efficiency and EGS reservoir lifespan would be significant to the sustainable development and utilization of geothermal energy.
