Coal Geology & Exploration


China has long been a global leader in the direct utilization of moderate- to low-temperature geothermal energy, in contrast to its sluggish progress in power generation using deep geothermal energy. Rocks in deep reservoirs exhibit decreased permeability under high-temperature and high-pressure conditions, necessitating the establishment of engineered geothermal system (EGS) for the exploitation of deep geothermal energy. In an EGS, hydraulic fracturing is employed for reservoir stimulation to create artificially enhanced geothermal reservoirs with higher permeability. The current techniques for deep geothermal reservoir stimulation are predominantly borrowed from hydraulic fracturing processes employed in the oil and gas sector, placing limitations on the stimulation performance, earthquake risk control, and efficient heat extraction of geothermal reservoirs. This study summarized the features of hydraulic fracturing for deep geothermal energy: (1) fracturing-induced damage is dominated by the shear mechanism. (2) The tensile stress generated by cold water injection-induced differential temperature encourages fractures to propagate further. (3) Continuous water injection keeps the wellbore pressure higher than the formation pressure, creating favorable conditions for fractures to maintain open. Therefore, no proppant is required for hydraulic fracturing in an EGS. This is totally different from the hydraulic fracturing of oil and gas wells for production growth, which relies heavily on proppants. Furthermore, this study systematically analyzed four major challenges to EGS: low power generation capacity, poor connectivity between injection and production wells, risks inducing damaging earthquakes, and difficult profit making with no subsidy. From the aspects of innovative fracturing and energy recycling, this study proposed an innovative enhanced development mode integrated with energy storage, termed regenerative engineered geothermal system (REGS). This study investigated the advantages of the REGS through numerical simulation. The results indicate that multistage fracturing using horizontal wells and unequal spacings, areas, and volumes of injected water can enhance the connectivity between injection and production wells. The fracturing process is optimized in the REGS. Specifically, multistage fracturing is adopted. In each fracturing, the water injection rate is rapidly increased in the early stage and gradually decreased in the late stage. This can avoid the abrupt fluctuations in the wellbore pressure, thus governing the magnitude of induced earthquakes and preventing damaging earthquakes. The REGS integrates large-scale underground storage of renewable energy, achieving multi-energy complementation and enhancing REGS projects’ production lifespan and profitability. The results of this study will lay the foundation for the pilot projects and standardization promotion of the technology for combined heat and power generation integrated with energy storage of deep geothermal energy in China.


Engineered Geothermal System (EGS), geothermal reservoir stimulation, proppant, induced earthquake, integration with energy storage




[1] MOOMAW W,BURGHERR P,HEATH G,et al. Annex II:Methodology[R]. IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation,2011.

[2] XIE Yachen,WU Xuning,HOU Zhengmeng,et al. Gleaning insights from German energy transition and large–scale underground energy storage for China’s carbon neutrality[J]. International Journal of Mining Science and Technology,2023,33(5):529−553.

[3] 庞忠和,罗霁,程远志,等. 中国深层地热能开采的地质条件评价[J]. 地学前缘,2020,27(1):134−151.

PANG Zhonghe,LUO Ji,CHENG Yuanzhi,et al. Evaluation of geological conditions for the development of deep geothermal energy in China[J]. Earth Science Frontiers,2020,27(1):134−151.

[4] 李根生,武晓光,宋先知,等. 干热岩地热资源开采技术现状与挑战[J]. 石油科学通报,2022,7(3):343−364.

LI Gensheng,WU Xiaoguang,SONG Xianzhi,et al. Status and challenges of hot dry rock geothermal resource exploitation[J]. Petroleum Science Bulletin,2022,7(3):343−364.

[5] 饶松,黄顺德,胡圣标,等. 中国陆区干热岩勘探靶区优选:来自国内外干热岩系统成因机制的启示[J]. 地球科学,2023,48(3):857−877.

RAO Song,HUANG Shunde,HU Shengbiao,et al. Exploration target selection of hot dry rock in Chinese continent:Enlightenment from genesis mechanism of global hot dry rock system[J]. Earth Science,2023,48(3):857−877.

[6] ZHANG Zhenguo,WANG Jiyang,REN Xiang,et al. The state–of–the–art and future development of geothermal energy in China country update report for the period 1996—2000[C]//World Geothermal Congress. Kyushu,2000:505−507.

[7] LUND J W,FREESTON D H. World–wide direct uses of geothermal energy 2000[J]. Geothermics,2001,30(1):29−68.

[8] TIAN Tingshan,DONG Ying,ZHANG Wei,et al. Rapid development of China’s geothermal industry–China national report of the 2020 world geothermal conference:World Geothermal Congress[C]//Proceedings of the World Geothermal Congress 2020+1. International Geothermal Association,Reykjavik,Iceland,2021:1–9.

[9] LUND J W,TOTH A N. Direct utilization of geothermal energy 2020 worldwide review[J]. Geothermics,2021,90:101915.

[10] 郑克棪,郑帆. 中国地热发电产业前景探讨[J]. 中外能源,2020,25(11):17−23.

ZHENG Keyan,ZHENG Fan. Discussion on prospects of geothermal power generation industry in China[J]. Sino–Global Energy,2020,25(11):17−23.

[11] 许天福,胡子旭,李胜涛,等. 增强型地热系统:国际研究进展与我国研究现状[J]. 地质学报,2018,92(9):1936−1947.

XU Tianfu,HU Zixu,LI Shengtao,et al. Enhanced geothermal system:International progresses and research status of China[J]. Acta Geologica Sinica,2018,92(9):1936−1947.

[12] AHINOAM P,ROLAND H,TAPAN M. What are the challenges in developing enhanced geothermal systems (EGS) observations from 64 EGS sites:World Geothermal Congress[C]//Proceedings of the World Geothermal Congress 2020. International Geothermal Association,Reykjavik,Iceland,2020:1–17.

[13] ENTINGH D J,JOHNSON S D,ALLIS R G,et al. A review of geothermal well stimulation experiments in the United States[J]. Transactions–Geothermal Resources Council,1999,23:175−179.

[14] NIITSUMA H. Fracture mechanics design and development of HDR reservoirs:Concept and results of the Γ–project,Tohoku university,Japan[J]. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts,1989,26(3/4):169−175.

[15] STOBER I. Depth– and pressure–dependent permeability in the upper continental crust:Data from the Urach 3 geothermal borehole,southwest Germany[J]. Hydrogeology Journal,2011,19(3):685−699.

[16] TESTER J,DIPIPPO R. The future of geothermal energy. Presentation at the doe geothermal program workshop[R]. Massachusetts Institute of Technology,Washington DC,2007.

[17] VERITY R V,CRICHLOW H B. Planning and execution of raft river stimulation treatments[R]. Santa Fe Springs:Republic Geothermal,Inc. ,1980.

[18] CORNET F H. Results from Le Mayet de Montagne project[J]. Geothermics,1987,16(4):355−374.

[19] 陈思源,刘浩,金衍,等. 压裂支撑剂发展综述与展望[J]. 石油科学通报,2023,8(3):330−346.

CHEN Siyuan,LIU Hao,JIN Yan,et al. Review and prospect of fracturing proppant development[J]. Petroleum Science Bulletin,2023,8(3):330−346.

[20] HOU Zhengmeng,ZHOU Lei,KRACKE T. Modelling of seismic events induced by reservoir stimulation in an enhanced geothermal system and a suggestion to reduce the deformation energy release[C]//Rock Dynamics and Applications. London:Taylor & Francis Group,2013:132808955.

[21] WU Lin,HOU Zhengmeng,XIE Yachen,et al. Fracture initiation and propagation of supercritical carbon dioxide fracturing in calcite–rich shale:A coupled thermal–hydraulic–mechanical–chemical simulation[J]. International Journal of Rock Mechanics and Mining Sciences,2023,167:105389.

[22] SU Donghua,HUANG Sheng,LI Zaoyuan,et al. Theoretical study on the hydraulic sealing integrity of cement sheath in horizontal shale oil wells under fracturing:Crack propagation mode and mechanism[J]. Advances in Mechanical Engineering,2022,14(6):1−20.

[23] SU Donghua,WU Xuning,LI Zaoyuan,et al. Theoretical analysis of the micro annulus of an oil–well cement sheath formed via cooling under acid–fracturing conditions[J]. Processes,2022,10(5):966.

[24] LU Shyimin. A global review of enhanced geothermal system (EGS)[J]. Renewable and Sustainable Energy Reviews,2018,81:2902−2921.

[25] 张森琦,严维德,黎敦朋,等. 青海省共和县恰卜恰干热岩体地热地质特征[J]. 中国地质,2018,45(6):1087−1102.

ZHANG Senqi,YAN Weide,LI Dunpeng,et al. Characteristics of geothermal geology of the Qiabuqia HDR in Gonghe Basin,Qinghai Province[J]. Geology in China,2018,45(6):1087−1102.

[26] 文冬光,张二勇,王贵玲,等. 干热岩勘查开发进展及展望[J]. 水文地质工程地质,2023,50(4):1−13.

WEN Dongguang,ZHANG Eryong,WANG Guiling,et al. Progress and prospect of hot dry rock exploration and development[J]. Hydrogeology and Engineering Geology,2023,50(4):1−13.

[27] ZHANG Eryong,WEN Dongguang,WANG Guiling,et al. The first power generation test of hot dry rock resources exploration and production demonstration project in the Gonghe Basin,Qinghai Province,China[J]. China Geology,2022,5(3):372−382.

[28] LEI Zhihong,ZHANG Yanjun,YU Ziwang,et al. Exploratory research into the enhanced geothermal system power generation project:The Qiabuqia geothermal field,northwest China[J]. Renewable Energy,2019,139:52−70.

[29] 尹欣欣,蒋长胜,翟鸿宇,等. 全球干热岩资源开发诱发地震活动和灾害风险管控[J]. 地球物理学报,2021,64(11):3817−3836.

YIN Xinxin,JIANG Changsheng,ZHAI Hongyu,et al. Review of induced seismicity and disaster risk control in dry hot rock resource development worldwide[J]. Chinese Journal of Geophysics,2021,64(11):3817−3836.

[30] 许天福,姜振蛟,袁益龙. 中深部地热资源开发利用研究现状与展望[J]. 中国基础科学,2023,25(3):11−22.

XU Tianfu,JIANG Zhenjiao,YUAN Yilong. Research status and prospects of middle and deep geothermal resources exploitation and utilization[J]. China Basic Science,2023,25(3):11−22.

[31] 许天福,袁益龙,姜振蛟,等. 干热岩资源和增强型地热工程:国际经验和我国展望[J]. 吉林大学学报(地球科学版),2016,46(4):1139−1152.

XU Tianfu,YUAN Yilong,JIANG Zhenjiao,et al. Hot dry rock and enhanced geothermal engineering:International experience and China prospect[J]. Journal of Jilin University (Earth Science Edition),2016,46(4):1139−1152.

[32] 陈作,许国庆,蒋漫旗. 国内外干热岩压裂技术现状及发展建议[J]. 石油钻探技术,2019,47(6):1−8.

CHEN Zuo,XU Guoqing,JIANG Manqi. The current status and development recommendations for dry hot rock fracturing technologies at home and abroad[J]. Petroleum Drilling Techniques,2019,47(6):1−8.

[33] 刘贺娟,童荣琛,侯正猛,等. 地下流体注采诱发地震综述及对深部高温岩体地热开发的影响[J]. 工程科学与技术,2022,54(1):83−96.

LIU Hejuan,TONG Rongchen,HOU Zhengmeng,et al. Review of induced seismicity caused by subsurface fluid injection and production and impacts on the geothermal energy production from deep high temperature rock[J]. Advanced Engineering Sciences,2022,54(1):83−96.

[34] HÄRING M O,SCHANZ U,LADNER F,et al. Characterisation of the basel 1 enhanced geothermal system[J]. Geothermics,2008,37(5):469−495.

[35] DYER B C,SCHANZ U,SPILLMANN T,et al. Application of microseismic multiplet analysis to the basel geothermal reservoir stimulation events[J]. Geophysical Prospecting,2010,58(5):788−804.

[36] GROOS J,ZEIB J,GRUND M,et al. Microseismicity at two geothermal power plants at Landau and Insheim in the Upper Rhine Graben,Germany[J]. Geophysical Research Abstracts,2013,15:1.

[37] MAJER E L,BARIA R,STARK M,et al. Induced seismicity associated with enhanced geothermal systems[J]. Geothermics,2007,36(3):185−222.

[38] YOST K,VALENTIN A,EINSTEIN H H. Estimating cost and time of wellbore drilling for engineered geothermal systems (EGS):Considering uncertainties[J]. Geothermics,2015,53:85−99.

[39] MICHAEL Z H,TOBIAS K,GOU Yang,et al. Einzelprojekt 6:THM:C gekoppelte Untersuchungen zu Mechanismen und freigesetzten Deformationsenergien der seismischen Ereignisse in der Reservoirstimulations-und Betriebsphase[R]. Technische Universität Clausthal,Goslar,2014.

[40] HARIS M,HOU Zhengmeng Michael,FENG Wentao,et al. A regenerative enhanced geothermal system for heat and electricity production as well as energy storage[J]. Renewable Energy,2022,197:342−358.

[41] XU Tianfu,YUAN Yilong,JIA Xiaofeng,et al. Prospects of power generation from an enhanced geothermal system by water circulation through two horizontal wells:A case study in the Gonghe Basin,Qinghai Province,China[J]. Energy,2018,148:196−207.

[42] ZHANG Yanjun,LI Zhengwei,GUO Liangliang,et al. Electricity generation from enhanced geothermal systems by oilfield produced water circulating through reservoir stimulated by staged fracturing technology for horizontal wells:A case study in Xujiaweizi area in Daqing Oilfield,China[J]. Energy,2014,78(Sup.1):788−805.

[43] LEI Zhihong,ZHANG Yanjun,ZHANG Senqi,et al. Electricity generation from a three–horizontal–well enhanced geothermal system in the Qiabuqia geothermal field,China:Slickwater fracturing treatments for different reservoir scenarios[J]. Renewable Energy,2020,145:65−83.

[44] STEFÁNSSON V. Investment cost for geothermal power plants[J]. Geothermics,2002,31(2):263−272.

[45] CHAMORRO C R,MONDÉJAR M E,RAMOS R,et al. World geothermal power production status:Energy,environmental and economic study of high enthalpy technologies[J]. Energy,2012,42(1):10−18.

[46] CHRISTOPH K,SHIVENES S,VERENA F,et al. Levelized cost of electricity:Renewable energy technologies[R]. Fraunhofer Institute for Solar Energy Systems ISE,2021.

[47] KABUTH A,DAHMKE A,BEYER C,et al. Energy storage in the geological subsurface:Dimensioning,risk analysis and spatial planning:The ANGUS plus project[J]. Environmental Earth Sciences,2017,76(1):1−17.

[48] SOMMER W T,DOORNENBAL P J,DRIJVER B C,et al. Thermal performance and heat transport in aquifer thermal energy storage[J]. Hydrogeology Journal,2014,22(1):263−279.



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