Coal Geology & Exploration


The geothermal heating technology utilizing moderately deep coaxial borehole heat exchangers (MDCBHEs) has emerged and found extensive applications in urban heating in northern China. Despite abundant geothermal resources, northern Shaanxi exhibits slightly low geothermal gradients and distinct thermophysical properties of rocks and soils. Therefore, geological parameters influence the heat transfer performance of MDCBHEs in this area. Using OpenGeoSys, an open-source numerical simulation platform, this study established a three-dimensional calculation model for heat transfer between a MDCBHE and surrounding strata. Based on typical geological parameters in northern Shaanxi, the study investigated the influence of various design parameters on the heat transfer performance of MDCBHEs, as well as their techno-economic feasibility during their life cycle. Finally, this study selected the optimal parameters of MDCBHEs for geothermal engineering. Results indicate that increasing the outer diameter of outer pipes and the burial depth can both enhance the heat extraction capacity of a MDCBHE. Notably, compared to the outer diameter of outer pipes, the burial depth produced more significant effects on the capacity. Specifically, the nominal heat transfer capacity increased by 77.3% when the burial depth rose from 2500 m to 3500 m. Engineering practices reveal that when the outer diameter of outer pipes exceeds 177.80 mm × 9.19 mm, the average energy cost will increase due to a sharp rise in drilling costs. Under the specific operating parameters, this study recommends that the optimal design parameters of MDCBHEs should comprise an outer diameter of outer pipes of 177.80 mm × 9.19 mm and a burial depth of 3200 m. In this case, the average energy cost is 0.524 CNY/(kW·h), suggesting the optimal economic benefits.


moderately deep, coaxial borehole heat exchanger, heat transfer performance, numerical simulation, economy, burial depth, pipe diameter, OpenGeoSys




[1] 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.

[2] 曲云霞,张林华,方肇洪,等. 地源热泵地下环路的设计方法[J]. 流体机械,2002,30(9):50−52.

QU Yunxia,ZHANG Linhua,FANG Zhaohong,et al. The ground loop design for ground–coupled heat pumps[J]. Fluid Machinery,2002,30(9):50−52.

[3] HENRIK H,JOSE A,ERLING N,et al. Thermal evaluation of coaxial deep borehole heat exchangers[J]. Renewable Energy,2016,97:65−76.

[4] WELSCH B,RUHAAK W,SCHULTE D O,et al. Characteristics of medium deep borehole thermal energy storage[J]. International Journal of Energy Research,2016,40(13):1855−1868.

[5] LE LOUS M,LARROQUE F,DUPUY A,et al. Thermal performance of a deep borehole heat exchanger:Insights from a synthetic coupled heat and flow model[J]. Geothermics,2015,57:157−172.

[6] ABDELHAFIZ M M,OPPELT J,MAHMOUD O,HEGELE L A. Effect of drilling and wellbore geometry parameters on wellbore temperature profile: Implications for geothermal production[J]. Advances in Geo-Energy Research,2023,8(3):170−180.

[7] 卜宪标,冉运敏,王令宝,等. 单井地热供暖关键因素分析[J]. 浙江大学学报(工学版),2019,53(5):957−964.

BU Xianbiao,RAN Yunmin,WANG Lingbao,et al. Analysis of key factors affecting single well geothermal heating[J]. Journal of Zhejiang University (Engineering Science),2019,53(5):957−964.

[8] 李鹏程. 中深层地热源热泵套管式地埋管换热器传热特性研究[D]. 哈尔滨:哈尔滨工业大学,2018.

LI Pengcheng. Research on heat transfer characteristics of casing ground heat exchanger with medium and deep ground source heat pump[D]. Harbin:Harbin Institute of Technology,2018.

[9] KOHL T,BRENNI R,EUGSTER W. System performance of a deep borehole heat exchanger[J]. Geothermics,2002,31:687−708.

[10] 黄建军,周阳,滕宏泉,等. 关中盆地西安凹陷地热水赋存特征及其资源量估算[J]. 西北地质,2021,54(1):196−203.

HUANG Jianjun,ZHOU Yang,TENG Hongquan,et al. On the occurrence characteristics and the estimation of geothermal water in Xi’an Sag,Guanzhong Basin[J]. Northwestern Geology,2021,54(1):196−203.

[11] 张薇,王贵玲,刘峰,等. 中国沉积盆地型地热资源特征[J]. 中国地质,2019,46(2):255−268.

ZHANG Wei,WANG Guiling,LIU Feng,et al. Characteristics of geothermal resources in sedimentary basins[J]. Geology in China,2019,46(2):255−268.

[12] 刘润川,任战利,叶汉青,等. 地热资源潜力评价:以鄂尔多斯盆地部分地级市和重点层位为例[J]. 地质通报,2021,40(4):565−576.

LIU Runchuan,REN Zhanli,YE Hanqing,et al. Potential evaluation of geothermal resources:Exemplifying some municipalities and key strata in Ordos Basin as a study case[J]. Geological Bulletin of China,2021,40(4):565−576.

[13] 陕西省地质矿产局. 陕西省区域地质志[M]. 北京:地质出版社,1989.

[14] 张育平,刘俊,王沣浩,等. 中深层地热能套管井取热影响因素分析[J]. 西安科技大学学报,2022,42(5):918−925.

ZHANG Yuping,LIU Jun,WANG Fenghao,et al. Analysis on the influencing factors of thermal extraction of medium–deep geothermal coaxial tube[J]. Journal of Xi’an University of Science and Technology,2022,42(5):918−925.

[15] KOLDITZ O,BAUER S,BILKE L,et al. OpenGeoSys:An open–source initiative for numerical simulation of thermo–hydro–mechanical/chemical (THM/C) processes in porous media[J]. Environmental Earth Sciences,2012,67(2):589−599.

[16] 孔彦龙,黄永辉,郑天元,等. 地热能可持续开发利用的数值模拟软件OpenGeoSys:原理与应用[J]. 地学前缘,2020,27(1):170−177.

KONG Yanlong,HUANG Yonghui,ZHENG Tianyuan,et al. Principle and application of OpenGeoSys for geothermal energy sustainable utilization[J]. Earth Science Frontiers,2020,27(1):170−177.

[17] LUO Yongqiang,YU Jinghua,YAN Tian,et al. Improved analytical modeling and system performance evaluation of deep coaxial borehole heat exchanger with segmented finite cylinder–source method[J]. Energy and Buildings,2020,212:109829.

[18] DIERSCH H J G,BAUER D,HEIDEMANN W,et al. Finite element modeling of borehole heat exchanger systems[J]. Computers & Geosciences,2011,37(8):1136−1147.

[19] WANG Zhihua,WANG Fenghao,LIU Jun,et al. Field test and numerical investigation on the heat transfer characteristics and optimal design of the heat exchangers of a deep borehole ground source heat pump system[J]. Energy Conversion and Management,2017,153:603−615.

[20] CAI Wanlong,WANG Fenghao,CHEN Shuang,et al. Analysis of heat extraction performance and long–term sustainability for multiple deep borehole heat exchanger array:A project–based study[J]. Applied Energy,2021,289:116590.

[21] 张健,董淼,王蓓羽,等. 陕西关中盆地地热资源及壳幔温度结构的地球物理分析[J]. 地球科学与环境学报,2021,43(1):150−163.

ZHANG Jian,DONG Miao,WANG Beiyu,et al. Geophysical analysis of geothermal resources and temperature structure of crust and Upper Mantle Beneath Guanzhong Basin of Shaanxi,China[J]. Journal of Earth Sciences and Environment,2021,43(1):150−163.

[22] CUI Yuanlong,ZHU Jie,TWAHA S,et al. Techno–economic assessment of the horizontal geothermal heat pump systems:A comprehensive review[J]. Energy Conversion and Management,2019,191:208−236.



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