Methods for assessing the circulation depth of geothermal water in a moderate- to low-temperature convective geothermal system and their applications

Authors

• LI Yiman, State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, ChinaFollow
• XIA Haoran, School of Earth Sciences and Surveying and Mapping Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
• GAO Binbin, State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
• SUN Wenjie, School of Earth Sciences and Surveying and Mapping Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
• PANG Zhonghe, State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, ChinaFollow

Abstract

Background The circulation depth of geothermal water is an important parameter for investigating geothermal systems or fields. It determines the thermal energy intensity and mineral composition of geothermal water, emerging as a critical factor influencing the efficient and sustainable development and utilization of geothermal resources.Progress This study presents a summary of the characteristics of typical moderate- to low-temperature convective geothermal systems from the perspective of sources (heat and fluid sources), pathways, geothermal reservoirs, cap rocks, and the geothermal water upwelling process and its impacts. Furthermore, this study systematically reviews suitable methods for assessing the circulation depth of geothermal water, as well as their fundamental principles, applicable conditions, and parameter acquisition approaches. The results indicate that primary assessment methods include geothermal heating methods and numerical simulation methods presently. Among these, geothermal heating methods require representative geothermal gradients, proving more suitable for conductive or conduction-dominated geothermal systems. In contrast, numerical simulation methods are established based on the mass and energy balance in heat exchange between the surrounding rocks and the upwelling geothermal water of a convective geothermal system. Based on the geometry of the pathways for fluid upwelling, the end-member models for numerical simulation can be divided into vertical-pipe and fault-plane models, both of which assume that during upwelling, geothermal water suffers from heat loss primarily due to its heat exchange with surrounding rocks. Geophysical exploration and interpretation methods can determine the spatial distributions of geothermal reservoirs and faults. However, due to limited accuracy and resolution, these methods generally yield qualitative or semi-quantitative results. Given their high implementation costs, it is recommended to combine these methods with borehole data to provide auxiliary support as joint constraints. Based on these analyses, this study proposes a scientific and reasonable process to assess the circulation depth of geothermal water. First, it is necessary to create a conceptual schema of a geothermal system and to determine the end-member model (a vertical pipe model or a fault-plane model) based on the way of geothermal water exposure. Next, 2−3 applicable geothermometer methods should be selected to calculate reliable reservoir temperatures. Finally, the circulation depth of geothermal water should be calculated by combining several parameters, including the thermal conductivity of rocks and the local annual average temperature. Previous studies have indicated that the Dengwu geothermal system in Fengshun County, Guangdong Province, represents a representative moderate- to low-temperature convective geothermal system in the coastal area in southeast China. Governed by NE- and NW-trending faults, the geothermal system exhibits a geothermal water exposure way consistent with the vertical pipe model, with a geothermal reservoir temperature of 143 ℃. Using the proposed assessment process, the circulation depth of geothermal water in the geothermal system was calculated at 6.0−7.0 km, aligning with the reservoir depth derived from the interpretations of magnetotelluric (MT) sounding.Prospects In the future, geophysical, geochemical, and numerical methods should be combined to determine reliable circulation depths of geothermal water. This effort will help quantify the contribution of convective heat to heat flux, thereby providing a scientific basis for preparing schemes for sustainable development and utilization of geothermal resources.

Keywords

moderate- to low-temperature convective geothermal system, geothermal heating method, circulation depth of geothermal water, numerical simulation method, Fengshun geothermal system

DOI

10.12363/issn.1001-1986.26.03.0133

Recommended Citation

LI Yiman, XIA Haoran, GAO Binbin, et al. (2026) "Methods for assessing the circulation depth of geothermal water in a moderate- to low-temperature convective geothermal system and their applications," Coal Geology & Exploration: Vol. 54: Iss. 6, Article 17.
DOI: 10.12363/issn.1001-1986.26.03.0133
Available at: https://cge.researchcommons.org/journal/vol54/iss6/17

Reference

[1] DIAMOND L W,WANNER C,WABER H N. Penetration depth of meteoric water in orogenic geothermal systems[J]. Geology,2018,46(12):1063−1066.

[2] LI Cuiming,MAO Xumei. Correction of the circulation depth of geothermal water based on temperature variation in the discharge section of geothermal system[J]. Environmental Earth Sciences,2024,83(19):552.

[3] MCINTOSH J C,FERGUSON G. Deep meteoric water circulation in earth’s crust[J]. Geophysical Research Letters,2021,48(5):e2020GL090461.

[4] RYBACH L. Deep groundwater circulation in Hercynian basement[J]. Environmental Geology,1997,32(2):137−141.

[5] LI Yiman,LUO Ji,TIAN Jiao,et al. Formation of the hydrothermal system from granite reservoir for power generation in igneous rock areas of South China[J]. Geothermics,2023,110:102673.

[6] MAO Xumei,ZHU Dongbo,NDIKUBWIMANA I,et al. The mechanism of high–salinity thermal groundwater in Xinzhou geothermal field,South China:Insight from water chemistry and stable isotopes[J]. Journal of Hydrology,2021,593:125889.

[7] 李义曼,罗霁,陈凯,等. 广东省丰良地热田高氟地热流体成因及热储温度评价[J]. 地质论评,2023,69(4):1337−1348 LI Yiman,LUO Ji,CHEN Kai,et al. Genesis of geothermal fluid with high fluorine content and reservoir temperature assessment in Fengliang geothermal field,eastern Guangdong[J]. Geological Review,2023,69(4):1337−1348

[8] LUO Lu,PANG Zhonghe,LIU Jinxia,et al. Determining the recharge sources and circulation depth of thermal waters in Xianyang geothermal field in Guanzhong Basin:The controlling role of Weibei Fault[J]. Geothermics,2017,69:55−64.

[9] 庞忠和,孔彦龙,庞菊梅,等. 雄安新区地热资源与开发利用研究[J]. 中国科学院院刊,2017,32(11):1224−1230 PANG Zhonghe,KONG Yanlong,PANG Jumei,et al. Geothermal resources and development in Xiong’an New Area[J]. Bulletin of Chinese Academy of Sciences,2017,32(11):1224−1230

[10] 汪集暘,庞忠和,孔彦龙,等. 我国地热清洁取暖产业现状与展望[J]. 科技促进发展,2020,16(3/4):294−298 WANG Jiyang,PANG Zhonghe,KONG Yanlong,et al. Status and prospects of geothermal clean heating industry in China[J]. Science & Technology for Development,2020,16(3/4):294−298

[11] 毛绪美,李翠明. 地热系统中地下水循环深度的重新评估[J]. 地学前缘,2025,32(5):220−229 MAO Xumei,LI Cuiming. Reassessment of the depth of groundwater circulation in geothermal systems[J]. Earth Science Frontiers,2025,32(5):220−229

[12] 王路瑶,刘凯,万力,等. 江西新泉–温汤断裂东段中低温地热流体水化学特征及成因机制[J]. 地球学报,2026,47(1):49−64 WANG Luyao,LIU Kai,WAN Li,et al. Hydrochemical characteristics and genetic mechanisms of mid–low temperature geothermal fluids in the eastern segment of the Xinquan–Wentang fault zone,Jiangxi Province[J]. Acta Geoscientica Sinica,2026,47(1):49−64

[13] 袁利娟,孔祥军,高剑,等. 北京市延庆地热田成因模式[J]. 地质论评,2020,66(4):933−941 YUAN Lijuan,KONG Xiangjun,GAO Jian,et al. Genetic model of the Yanqing geothermal field,Beijing[J]. Geological Review,2020,66(4):933−941

[14] SOREY M L,LEWIS R E. Convective heat flow from hot springs in the Long Valley Caldera,Mono County,California[J]. Journal of Geophysical Research,1976,81(5):785−791.

[15] SOREY M L. Numerical modeling of liquid geothermal systems[R]. Reston，VA：U. S. Geological Survey，1978.

[16] RYBACH L. Determination of thermal water circulation depth，with examples from the Valaisan Alps，Switzerland[C]//Proc. IAHS/IAH Symposium on Water Resources in Mountainous Regions. Lausanne：IAH Mémoires XXII/1，1983：608–615.

[17] 熊亮萍,汪集暘,庞忠和. 漳州热田地下热水的循环深度[J]. 地质科学,1990(4):377−384 XIONG Liangping,WANG Jiyang,PANG Zhonghe. Circulation depth of the thermal water in Zhangzhou geothermal field[J]. Scientia Geologica Sinica,1990(4):377−384

[18] 柳富田,苏小四,董维红,等. 同位素技术在地下水循环深度确定中的应用[J]. 人民黄河,2008,30(4):52−54

[19] 童小畅,唐忠全,满向杰,等. 广域电磁法在滇西造山带地热通道识别中的应用研究:以澜沧上允地区为例[J]. 中国有色金属学报,2026,36(2):598−610 TONG Xiaochang,TANG Zhongquan,MAN Xiangjie,et al. Application of wide–field electromagnetic method in identification of geothermal channels in western Yunnan Orogenic Belt:A case study of Shangyun area in Lancang[J]. The Chinese Journal of Nonferrous Metals,2026,36(2):598−610

[20] MUFFLER L P J. Tectonic and hydrologic control of the nature and distribution of geothermal resources[C]//Second U. N. Symposium on the Development and Use of Geothermal Resources. San Francisco，1976：499–507.

[21] 汪集旸. 中低温对流型地热系统[M]. 北京：科学出版社，1993.

[22] HAO Yinlei,PANG Zhonghe,TIAN Jiao,et al. Origin and evolution of hydrogen–rich gas discharges from a hot spring in the eastern coastal area of China[J]. Chemical Geology,2020,538:119477.

[23] TIAN Jiao,STEFÁNSSON A,LI Yiman,et al. Geochemistry of thermal fluids and the genesis of granite–hosted Huangshadong geothermal system,southeast China[J]. Geothermics,2023,109:102647.

[24] 庞忠和. 漳州盆地地热系统：成因模式、热能潜力与热水分布规律的研究[D]. 北京：中国科学院地质所，1987. PANG Zhonghe. Zhangzhou basin geothermal system：genesis model，energy potential and the occurrence of thermal water[D]. Beijing：Institute of Geology，Chinese Academy of Sciences，1987.

[25] PANG Jumei,PANG Zhonghe,LYU Min,et al. Geochemical and isotopic characteristics of fluids in the Niutuozhen geothermal field,North China[J]. Environmental Earth Sciences,2018,77:12.

[26] TIAN Jiao,LI Yiman,ZHOU Xiaocheng,et al. Geochemical characteristics of hydrothermal volatiles from southeast China and their implications on the tectonic structure controlling heat convection[J]. Frontiers in Earth Science,2021,9:786051.

[27] LIAO Lixia,ZHOU Yueyong,LIN Zhiying,et al. Gas geochemistry of the hot springs gas in Fujian Province,SE China:Insight into the deep faults and seismic activity[J]. Frontiers in Earth Science,2023,11:1277100.

[28] 崔洋,康凤新,钟振楠,等. 鲁西北平原地热热源机制的气体同位素约束[J]. 地球学报,2023,44(1):93−106 CUI Yang,KANG Fengxin,ZHONG Zhennan,et al. Gas isotope constraints on the geothermal heat source mechanism in northwest Shandong Plain[J]. Acta Geoscientica Sinica,2023,44(1):93−106

[29] 袁建飞. 广东沿海地热系统水文地球化学研究[D]. 武汉：中国地质大学，2013. YUAN Jianfei. Hydrogeochemistry of the geothermal systems in coastal areas of Guangdong Province，South China[D]. Wuhan：China University of Geosciences，2013.

[30] 汪啸. 广东沿海典型深大断裂带地热水系统形成条件及水文地球化学特征[D]. 武汉：中国地质大学，2018. WANG Xiao. Formation conditions and hydrogeochemical characteristics of the geothermal water in typical coastal geothermal field with deep faults，Guangdong Province[D]. Wuhan：China University of Geosciences，2018.

[31] 庞忠和,段忠丰. 华北赋煤区地热资源富集模式及开发利用方向[J]. 煤田地质与勘探,2024,52(9):14−22 PANG Zhonghe,DUAN Zhongfeng. Accumulation patterns and exploitation and utilization targets of geothermal resources in the coal–bearing area in North China[J]. Coal Geology & Exploration,2024,52(9):14−22

[32] 胡婷. 阳江新洲千米地热钻孔地温梯度特征分析[D]. 武汉：中国地质大学，2014. HU Ting. Geothermal gradient characteristics analysis of a kilometer geothermal drilling in Xinzhou geothermal field，Yangjiang，China[D]. Wuhan：China University of Geosciences，2014.

[33] WANG Xiaolin,YAN Xiaoxue,ZHANG Wei,et al. Hydrogeochemical characteristics and evolutionary mechanisms of the Nanping geothermal field,southeastern Hainan Island,China[J]. Sustainability,2025,17(13):6189.

[34] 李馥锶. 广东丰顺地热田水化学特征及成因机制研究[D]. 武汉：中国地质大学，2017. LI Fusi. Study on chemical characteristics and origin mechanism of Fengshun geothermal fields in Guangdong Province[D]. Wuhan：China University of Geosciences，2017.

[35] 罗霁. 广东丰顺典型地热田热水成因研究[R]. 北京：中国科学院地质与地球物理研究所博士后出站报告，2020.

[36] CHENG Yuanzhi,HAN Bo,LI Yiman,et al. Lithospheric electrical structure beneath the Cathaysia Block in South China and its tectonic implications[J]. Tectonophysics,2021,814:228981.

[37] LI Jianhua,DONG Shuwen,GAO Rui,et al. The thinnest crust in South China associated with the Cretaceous lithospheric extension:Evidence from SINOPROBE seismic reflection profiling[J]. Tectonics,2022,41(8):e2022TC007240.

[38] 福建省地矿局. 区域地质调查报告(1∶20万)福州幅福清幅南日岛幅[R]. 福州：福建省区域地质测量队，1977.