To address the challenge of rapidly and accurately quantifying the heat performance of energy tunnels under unknown operational conditions, this study proposes an intelligent predictive framework that integrates multi-physics simulation and explainable machine learning. A validated three-dimensional multi-physics model was developed in COMSOL to generate a dataset comprising 1024 simulation samples covering ten key operational parameters. Nine machine learning algorithms were employed to construct predictive models for the heat performance of energy tunnels, and Shapley Additive Explanations (SHAP) were applied to enhance model interpretability. Results demonstrate that the Support Vector Regression (SVR) model achieved the highest predictive accuracy (R² = 0.961), while the Back Propagation Neural Network (BPNN) model exhibited the lowest average absolute error (AE) on the test set (AEavg = 2.76 W/m²). The tunnel air temperature (Ta), fluid velocity (Vf), and air convective heat transfer coefficient (h) were identified as the most influential factors affecting the heat performance, with significant interactions observed among multiple parameters. This study provides a reliable data-driven basis for the intelligent prediction and optimization of energy tunnel heat performance.
{"title":"Explainable machine learning models to predict the heat performance of energy tunnels","authors":"Lifei Zheng , Wenbo Yu , Zhi Chen , Sheng Yang , Zhiying Zhong , Henglin Xiao","doi":"10.1016/j.geothermics.2025.103508","DOIUrl":"10.1016/j.geothermics.2025.103508","url":null,"abstract":"<div><div>To address the challenge of rapidly and accurately quantifying the heat performance of energy tunnels under unknown operational conditions, this study proposes an intelligent predictive framework that integrates multi-physics simulation and explainable machine learning. A validated three-dimensional multi-physics model was developed in COMSOL to generate a dataset comprising 1024 simulation samples covering ten key operational parameters. Nine machine learning algorithms were employed to construct predictive models for the heat performance of energy tunnels, and Shapley Additive Explanations (SHAP) were applied to enhance model interpretability. Results demonstrate that the Support Vector Regression (SVR) model achieved the highest predictive accuracy (R² = 0.961), while the Back Propagation Neural Network (BPNN) model exhibited the lowest average absolute error (AE) on the test set (AE<sub>avg</sub> = 2.76 W/m²). The tunnel air temperature (<em>T</em><sub>a</sub>), fluid velocity (<em>V</em><sub>f</sub>), and air convective heat transfer coefficient (<em>h</em>) were identified as the most influential factors affecting the heat performance, with significant interactions observed among multiple parameters. This study provides a reliable data-driven basis for the intelligent prediction and optimization of energy tunnel heat performance.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103508"},"PeriodicalIF":3.9,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145332986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1016/j.geothermics.2025.103507
Yuhzong Liao , Guiling Wang , Wei Zhang , Hanxiong Zhang , Jiyun Liang , Yufei Xi
This study investigates fault-controlled geothermal systems in southeastern China, focusing on representative regions in Hunan, Guangdong, and Jiangxi provinces. A machine learning approach—non-negative matrix factorization with k-means clustering (NMFk)—was applied to classify geothermal water types and delineate favorable exploration zones based on hydrochemical composition, flow rate, heat flow, and fault proximity. Geothermal waters were classified into three types with distinct geochemical and geological attributes: Type A, Type B, and Type C. Representative geothermal fields—Nuanshui (Type A), Longmen and Reshui (Type B), and Chengkou (Type C)—were selected to validate the classification and analyze reservoir characteristics and genetic mechanisms. Type B geothermal water exhibits the highest exploration potential, characterized by deep circulation (1900–5300 m), high reservoir temperatures (66–143 °C), strong confinement, and enrichment in Na⁺ and Li⁺. Its formation is primarily controlled by NW-trending faults and high heat-producing granites. Type C geothermal water shows moderate potential, with the highest heat flow (83 mW/m²), deep circulation (3500–5400 m), and elevated temperatures (109–127 °C), despite lower flow rates. It is hosted in granitic reservoirs associated with NE–N-trending faults. In contrast, Type A demonstrates the lowest geothermal potential, featuring shallow circulation (900–2100 m), lower temperatures (42–75 °C), high flow rates, and enrichment in Mg²⁺, Ca²⁺, and Sr²⁺, reflecting strong meteoric recharge and limited geochemical evolution. A conceptual model is proposed in which meteoric water infiltrates through fault zones, absorbs heat during deep circulation within granitic or carbonate rocks, and ascends to form geothermal reservoirs or surface springs. The classification results align well with spatial patterns of geothermal favorability, offering a robust framework for geothermal resource assessment and supporting sustainable development strategies in southeastern China.
{"title":"Machine learning for fault-controlled geothermal systems exploration in Chenzhou and Huizhou region, Southeast China","authors":"Yuhzong Liao , Guiling Wang , Wei Zhang , Hanxiong Zhang , Jiyun Liang , Yufei Xi","doi":"10.1016/j.geothermics.2025.103507","DOIUrl":"10.1016/j.geothermics.2025.103507","url":null,"abstract":"<div><div>This study investigates fault-controlled geothermal systems in southeastern China, focusing on representative regions in Hunan, Guangdong, and Jiangxi provinces. A machine learning approach—non-negative matrix factorization with k-means clustering (NMF<em>k</em>)—was applied to classify geothermal water types and delineate favorable exploration zones based on hydrochemical composition, flow rate, heat flow, and fault proximity. Geothermal waters were classified into three types with distinct geochemical and geological attributes: Type A, Type B, and Type C. Representative geothermal fields—Nuanshui (Type A), Longmen and Reshui (Type B), and Chengkou (Type C)—were selected to validate the classification and analyze reservoir characteristics and genetic mechanisms. Type B geothermal water exhibits the highest exploration potential, characterized by deep circulation (1900–5300 m), high reservoir temperatures (66–143 °C), strong confinement, and enrichment in Na⁺ and Li⁺. Its formation is primarily controlled by NW-trending faults and high heat-producing granites. Type C geothermal water shows moderate potential, with the highest heat flow (83 mW/m²), deep circulation (3500–5400 m), and elevated temperatures (109–127 °C), despite lower flow rates. It is hosted in granitic reservoirs associated with NE–N-trending faults. In contrast, Type A demonstrates the lowest geothermal potential, featuring shallow circulation (900–2100 m), lower temperatures (42–75 °C), high flow rates, and enrichment in Mg²⁺, Ca²⁺, and Sr²⁺, reflecting strong meteoric recharge and limited geochemical evolution. A conceptual model is proposed in which meteoric water infiltrates through fault zones, absorbs heat during deep circulation within granitic or carbonate rocks, and ascends to form geothermal reservoirs or surface springs. The classification results align well with spatial patterns of geothermal favorability, offering a robust framework for geothermal resource assessment and supporting sustainable development strategies in southeastern China.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103507"},"PeriodicalIF":3.9,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-09DOI: 10.1016/j.geothermics.2025.103510
Linlin Zhang , Dongyang Fan , Yanbin Li , Tianhao Yuan , Jun Chen
The growing interest in geothermal energy as a low-carbon alternative underscores the need for precise thermal characterization of subsurface environments. To enhance the design accuracy and operational reliability of ground source heat pump systems under complex geological conditions, this study builds an improved model that simultaneously accounts for soil stratification and groundwater advection to evaluate the thermal performance of borehole heat exchangers. A three-dimensional numerical model was established in ANSYS to simulate coupled heat transfer within multi-layered soil under summer-mode operation and was validated against in-situ thermal response test data, demonstrating errors below 5 %. Results indicate that neglecting soil stratification can lead to deviations of up to 18.6 % in thermal influence distance and 8.4 % in heat transfer efficiency, potentially risking underestimation of borehole spacing and system performance. Moreover, incorporating groundwater advection in the 3rd soil layer enhances convective heat transport, lowering outlet water temperatures by 0.6 °C and improving heat transfer efficiency by 40.96 %, while the proposed groundwater advection influence rate reached a maximum of 10.97 %. These findings demonstrate that both stratification and advection affect temperature distribution and thermal performance of soil, offering crucial insights for optimizing borehole design, spacing, and long-term GSHP operations in heterogeneous aquifer environments. This work provides critical insights for optimizing ground source heat pump systems under complex geological conditions, enabling more accurate heat exchange predictions and efficient multi-borehole layouts in practical applications.
{"title":"Thermal performance assessment of coupled soil stratification and groundwater advection effects on vertical borehole heat exchanger","authors":"Linlin Zhang , Dongyang Fan , Yanbin Li , Tianhao Yuan , Jun Chen","doi":"10.1016/j.geothermics.2025.103510","DOIUrl":"10.1016/j.geothermics.2025.103510","url":null,"abstract":"<div><div>The growing interest in geothermal energy as a low-carbon alternative underscores the need for precise thermal characterization of subsurface environments. To enhance the design accuracy and operational reliability of ground source heat pump systems under complex geological conditions, this study builds an improved model that simultaneously accounts for soil stratification and groundwater advection to evaluate the thermal performance of borehole heat exchangers. A three-dimensional numerical model was established in ANSYS to simulate coupled heat transfer within multi-layered soil under summer-mode operation and was validated against in-situ thermal response test data, demonstrating errors below 5 %. Results indicate that neglecting soil stratification can lead to deviations of up to 18.6 % in thermal influence distance and 8.4 % in heat transfer efficiency, potentially risking underestimation of borehole spacing and system performance. Moreover, incorporating groundwater advection in the 3rd soil layer enhances convective heat transport, lowering outlet water temperatures by 0.6 °C and improving heat transfer efficiency by 40.96 %, while the proposed groundwater advection influence rate reached a maximum of 10.97 %. These findings demonstrate that both stratification and advection affect temperature distribution and thermal performance of soil, offering crucial insights for optimizing borehole design, spacing, and long-term GSHP operations in heterogeneous aquifer environments. This work provides critical insights for optimizing ground source heat pump systems under complex geological conditions, enabling more accurate heat exchange predictions and efficient multi-borehole layouts in practical applications.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103510"},"PeriodicalIF":3.9,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The advantage of suitable anti-scaling technologies for individual geothermal plants would benefit from shorter development periods, making it necessary to improve the precision in evaluating a scaling technology through laboratory testing. This study focuses on developing a technology to replicate the scale formed in the Takigami binary geothermal plant. The artificial scale obtained was compared with an actual scale collected during jet washing that followed the chemical washing process in the evaporator of the Takigami binary power plant. The artificial scale was synthesized in controlled environments by removing dissolved oxygen and introducing carbon dioxide (CO2) to simulate geothermal conditions. The artificial scale resembled the natural scale, predominantly comprising silica and metal silicates. Although the scale formed in the Takigami binary geothermal plant differed from the artificial scale in terms of particle size, the size of the dispersion particles in the geothermal brine was similar to that of the dispersion particles in the synthesized solution. In addition, the amounts of enriched elements differed from those in the natural scale, with higher aluminum and lower calcium concentrations. These discrepancies highlight the need for additional adjustments in synthesis conditions to more precisely replicate the natural scaling environment. We illustrate how laboratory-scale synthesis can help successfully imitate the intricate natural scaling processes, providing valuable insights for enhancing scaling management in geothermal facilities. Optimizing the gas and chemical inputs may help further improve the precision of these simulations. The interactions between the material and solution particles need careful consideration.
{"title":"Method for imitating scale formation in the Takigami binary power plant in Oita, Japan: Establishment of primary synthesis conditions","authors":"Shota Ikemoto , Htoo Nay Wunn , Shinichi Motoda , Azusa Wada , Hirono Okano , Shinya Ui , Motoaki Morita","doi":"10.1016/j.geothermics.2025.103504","DOIUrl":"10.1016/j.geothermics.2025.103504","url":null,"abstract":"<div><div>The advantage of suitable anti-scaling technologies for individual geothermal plants would benefit from shorter development periods, making it necessary to improve the precision in evaluating a scaling technology through laboratory testing. This study focuses on developing a technology to replicate the scale formed in the Takigami binary geothermal plant. The artificial scale obtained was compared with an actual scale collected during jet washing that followed the chemical washing process in the evaporator of the Takigami binary power plant. The artificial scale was synthesized in controlled environments by removing dissolved oxygen and introducing carbon dioxide (CO<sub>2</sub>) to simulate geothermal conditions. The artificial scale resembled the natural scale, predominantly comprising silica and metal silicates. Although the scale formed in the Takigami binary geothermal plant differed from the artificial scale in terms of particle size, the size of the dispersion particles in the geothermal brine was similar to that of the dispersion particles in the synthesized solution. In addition, the amounts of enriched elements differed from those in the natural scale, with higher aluminum and lower calcium concentrations. These discrepancies highlight the need for additional adjustments in synthesis conditions to more precisely replicate the natural scaling environment. We illustrate how laboratory-scale synthesis can help successfully imitate the intricate natural scaling processes, providing valuable insights for enhancing scaling management in geothermal facilities. Optimizing the gas and chemical inputs may help further improve the precision of these simulations. The interactions between the material and solution particles need careful consideration.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103504"},"PeriodicalIF":3.9,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-30DOI: 10.1016/j.geothermics.2025.103505
Daniil S. Krutenko, Margarita F. Krutenko, Yuriy V. Kolmakov
While geothermal potential is typically assessed in tectonically active regions, sedimentary basins in stable areas also represent significant geothermal resources. Accurate assessment of geothermal potential in sedimentary basins requires understanding thermal field heterogeneity – the central research problem addressed in this work. We analyze a heat flow map of the southeastern Western Siberia sedimentary basin, derived from 433 well-based calculations.
To determine the heat flow density at the basement-sediment interface, we applied Valery Isaev's methodology via the 1D thermal modelling program Teplodialog. This technique is founded on a numerical solution of the heat conduction equation for a horizontally layered solid body with a mobile upper boundary. The resulting data were interpolated using the Kriging geostatistical method to generate a schematic heat flow map. The constructed map (contour interval 2 mW·m⁻²) demonstrates reliability through a strong correlation of its anomalous zones with data from prior studies.
Our findings reveal that heat flow distribution in sedimentary basins fundamentally correlates with the age of the last tectonomagmatic event – the primary control governing thermal patterns. This relationship explains observed connections between heat flow and both fault density (positive correlation in zones of recent tectonomagmatic activity) and basement rock composition (inherited from tectonic evolution history). Local variations in rock thermal properties account for only minor heat flow differences within coeval tectonic units.
{"title":"Geological controls on heat flow distribution in the southeastern Western Siberian Basin: Insights from thermal modeling","authors":"Daniil S. Krutenko, Margarita F. Krutenko, Yuriy V. Kolmakov","doi":"10.1016/j.geothermics.2025.103505","DOIUrl":"10.1016/j.geothermics.2025.103505","url":null,"abstract":"<div><div>While geothermal potential is typically assessed in tectonically active regions, sedimentary basins in stable areas also represent significant geothermal resources. Accurate assessment of geothermal potential in sedimentary basins requires understanding thermal field heterogeneity – the central research problem addressed in this work. We analyze a heat flow map of the southeastern Western Siberia sedimentary basin, derived from 433 well-based calculations.</div><div>To determine the heat flow density at the basement-sediment interface, we applied Valery Isaev's methodology via the 1D thermal modelling program Teplodialog. This technique is founded on a numerical solution of the heat conduction equation for a horizontally layered solid body with a mobile upper boundary. The resulting data were interpolated using the Kriging geostatistical method to generate a schematic heat flow map. The constructed map (contour interval 2 mW·m⁻²) demonstrates reliability through a strong correlation of its anomalous zones with data from prior studies.</div><div>Our findings reveal that heat flow distribution in sedimentary basins fundamentally correlates with the age of the last tectonomagmatic event – the primary control governing thermal patterns. This relationship explains observed connections between heat flow and both fault density (positive correlation in zones of recent tectonomagmatic activity) and basement rock composition (inherited from tectonic evolution history). Local variations in rock thermal properties account for only minor heat flow differences within coeval tectonic units.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103505"},"PeriodicalIF":3.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145227794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-27DOI: 10.1016/j.geothermics.2025.103503
Y.A. Popov, E.M. Chekhonin, E.G. Savelev, R.A. Romushkevich, M.Y. Spasennykh
For the first time in the marine geothermal research practice, multiscale rock heterogeneity and anisotropy were studied with continuous thermal property profiling on whole core column from shallow stratigraphic wells on the Kara Sea shelf that improved heat flow assessment. The thermophysical core logging technology, which allows specialists to provide continuous non-destructive profiling of rock thermal properties with spatial resolution of 1 mm, was utilized for the first time in marine wells. This approach yielded high-quality data on thermal conductivity, volumetric heat capacity, and thermal diffusivity for all drilled 916 full-size core samples, accounting for their thermal heterogeneity and anisotropy. Additionally, 30 core samples were selected based on thermal profiling results for extended thermophysical studies: 25 samples were scanned after additional saturation, 5 samples were prepared and studied within the temperature range from 20 to 80 °C using the divided bar technique, and 5 samples were studied at increased up to 5 MPa uniaxial pressure. Heat flow was estimated using the equivalent thermal conductivity, which was determined accounting for each core sample length, macro- and microanisotropy of the rocks, the core decompression, the drying of samples during transportation and storage, and thermobaric conditions of the drilled sediments. The research aims to create a database on geothermal characteristics to improve the reliability of hydrocarbon exploration and development on the studied territory of the Kara Sea shelf. The applied technology for experimental geothermal research allows specialists for extensive and more representative studies of the subsurface geothermal characteristics on the shelf, compared to the traditional approaches that rely on measurements in near-bottom sediments.
{"title":"Marine geothermal study in shallow stratigraphic wells on the Kara sea shelf: high-resolution thermal conductivity and temperature data","authors":"Y.A. Popov, E.M. Chekhonin, E.G. Savelev, R.A. Romushkevich, M.Y. Spasennykh","doi":"10.1016/j.geothermics.2025.103503","DOIUrl":"10.1016/j.geothermics.2025.103503","url":null,"abstract":"<div><div>For the first time in the marine geothermal research practice, multiscale rock heterogeneity and anisotropy were studied with continuous thermal property profiling on whole core column from shallow stratigraphic wells on the Kara Sea shelf that improved heat flow assessment. The thermophysical core logging technology, which allows specialists to provide continuous non-destructive profiling of rock thermal properties with spatial resolution of 1 mm, was utilized for the first time in marine wells. This approach yielded high-quality data on thermal conductivity, volumetric heat capacity, and thermal diffusivity for all drilled 916 full-size core samples, accounting for their thermal heterogeneity and anisotropy. Additionally, 30 core samples were selected based on thermal profiling results for extended thermophysical studies: 25 samples were scanned after additional saturation, 5 samples were prepared and studied within the temperature range from 20 to 80 °C using the divided bar technique, and 5 samples were studied at increased up to 5 MPa uniaxial pressure. Heat flow was estimated using the equivalent thermal conductivity, which was determined accounting for each core sample length, macro- and microanisotropy of the rocks, the core decompression, the drying of samples during transportation and storage, and thermobaric conditions of the drilled sediments. The research aims to create a database on geothermal characteristics to improve the reliability of hydrocarbon exploration and development on the studied territory of the Kara Sea shelf. The applied technology for experimental geothermal research allows specialists for extensive and more representative studies of the subsurface geothermal characteristics on the shelf, compared to the traditional approaches that rely on measurements in near-bottom sediments.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103503"},"PeriodicalIF":3.9,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-23DOI: 10.1016/j.geothermics.2025.103502
Zheng Zhen , Kun Yu , Zhijun Wan , Yiwen Ju , Zhenzi Yu , Zhuting Wang , Bo Zhang , Peng Shi , Zhehan Sun , Jiakun Lv
The deep mine holds substantial geothermal energy and presents favorable conditions for exploitation and utilization but lack effective engineering applications. The concept of “geothermal energy accumulation mechanism - location of reservoirs - development planning integrated with the mine system - utilization and economic assessment” was proposed and applied in this study. Geochemical studies of geothermal water have indicated the main type is Na-Ca-HCO3-SO4. The temperature of the thermal reservoir is 69.75 °C. Isotope indicators (δ18O and δD) suggest that the main source of geothermal water is meteoric water. Combined with numerical simulation to analyze the geothermal energy accumulation mechanism of No.10 mine. Surface limestone outcrops and faults constitute the water-conducting seepage channel, and geothermal water is concentrated in Likou syncline’s axis to form the thermal reservoir. The water-rich area was identified using underground transient electromagnetic method. A geothermal water development and utilization system was established based on the mine layout, which can meet 83,125 m2 of heating. The net income from the geothermal water development and utilization project is $ 412,990 per year. Compared with coal-fired heating, it can reduce CO2 emissions by 9471 tons/year, thereby contributing to a cleaner transition for the coal mine.
{"title":"Geothermal energy accumulation mechanism and development mode in a deep mine: A case study","authors":"Zheng Zhen , Kun Yu , Zhijun Wan , Yiwen Ju , Zhenzi Yu , Zhuting Wang , Bo Zhang , Peng Shi , Zhehan Sun , Jiakun Lv","doi":"10.1016/j.geothermics.2025.103502","DOIUrl":"10.1016/j.geothermics.2025.103502","url":null,"abstract":"<div><div>The deep mine holds substantial geothermal energy and presents favorable conditions for exploitation and utilization but lack effective engineering applications. The concept of “geothermal energy accumulation mechanism - location of reservoirs - development planning integrated with the mine system - utilization and economic assessment” was proposed and applied in this study. Geochemical studies of geothermal water have indicated the main type is Na-Ca-HCO<sub>3</sub>-SO<sub>4</sub>. The temperature of the thermal reservoir is 69.75 °C. Isotope indicators (δ<sup>18</sup>O and δ<sub>D</sub>) suggest that the main source of geothermal water is meteoric water. Combined with numerical simulation to analyze the geothermal energy accumulation mechanism of No.10 mine. Surface limestone outcrops and faults constitute the water-conducting seepage channel, and geothermal water is concentrated in Likou syncline’s axis to form the thermal reservoir. The water-rich area was identified using underground transient electromagnetic method. A geothermal water development and utilization system was established based on the mine layout, which can meet 83,125 m<sup>2</sup> of heating. The net income from the geothermal water development and utilization project is $ 412,990 per year. Compared with coal-fired heating, it can reduce CO<sub>2</sub> emissions by 9471 tons/year, thereby contributing to a cleaner transition for the coal mine.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103502"},"PeriodicalIF":3.9,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145121046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-23DOI: 10.1016/j.geothermics.2025.103500
Adolph Bravo Jr. , Erlend Straume , Ben Robinson , Namrata Kale , Harry Froment , Amir Shamsa , Maria Eleni Mitzithra , Barnaby E. King , Andri Stefánsson
The design and operation of geothermal wells, pipelines, and associated infrastructure depend on accurate analysis and understanding of multiphase flow behavior. While a variety of multiphase flow models are available, most are based on experimental data obtained under near-ambient conditions for air–water or oil–gas systems. Applying these models to high-temperature geothermal fluids potentially results in substantial inaccuracies, highlighting the need to investigate multiphase flow under conditions relevant to geothermal applications. Here we introduce the Geothermal-Flowloop (GFL)—a novel, purpose-built facility for direct observation and analysis of multiphase flow in geothermal fluids at representative temperatures and pressures. The system enables controlled multiphase flow experiments with water or brine and gases at temperatures up to 200 °C and pressures up to 40 bar. Equipped with an optical window, hydrophone, and gamma densitometers, the GFL allows real-time and direct visualization of fluid flow behavior including identification of flow regimes, cavitation, slip, liquid holdup and void fraction determination. The GFL also offers a platform for evaluating emerging technologies with potential geothermal applications. By facilitating detailed investigations under realistic operating conditions, the facility contributes to the advancement of geothermal infrastructure design and performance optimization.
{"title":"Geothermal-Flowloop (GFL): Investigating multiphase flows under geothermal conditions","authors":"Adolph Bravo Jr. , Erlend Straume , Ben Robinson , Namrata Kale , Harry Froment , Amir Shamsa , Maria Eleni Mitzithra , Barnaby E. King , Andri Stefánsson","doi":"10.1016/j.geothermics.2025.103500","DOIUrl":"10.1016/j.geothermics.2025.103500","url":null,"abstract":"<div><div>The design and operation of geothermal wells, pipelines, and associated infrastructure depend on accurate analysis and understanding of multiphase flow behavior. While a variety of multiphase flow models are available, most are based on experimental data obtained under near-ambient conditions for air–water or oil–gas systems. Applying these models to high-temperature geothermal fluids potentially results in substantial inaccuracies, highlighting the need to investigate multiphase flow under conditions relevant to geothermal applications. Here we introduce the Geothermal-Flowloop (GFL)—a novel, purpose-built facility for direct observation and analysis of multiphase flow in geothermal fluids at representative temperatures and pressures. The system enables controlled multiphase flow experiments with water or brine and gases at temperatures up to 200 °C and pressures up to 40 bar. Equipped with an optical window, hydrophone, and gamma densitometers, the GFL allows real-time and direct visualization of fluid flow behavior including identification of flow regimes, cavitation, slip, liquid holdup and void fraction determination. The GFL also offers a platform for evaluating emerging technologies with potential geothermal applications. By facilitating detailed investigations under realistic operating conditions, the facility contributes to the advancement of geothermal infrastructure design and performance optimization.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103500"},"PeriodicalIF":3.9,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145121045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-23DOI: 10.1016/j.geothermics.2025.103479
Xiaoxiao Yin , Bowen Xu , Jian Shen , Zhenhai Zong , Guangyao Zhang , Zhilong Liu , Jinghong Hu
Geothermal reservoir dynamic monitoring and research serve as the key scientific foundation for optimizing resource development, ensuring sustainable utilization, and mitigating exploitation risks. This paper systematically compiles nearly 50 years of geothermal utilization demand and management policies in Tianjin, along with data on application scenarios, extraction/injection volumes, thermal reservoir water levels, hydrochemical components, wellhead temperatures, and thermal reservoir temperatures for both porous (e.g., Guantao Formation) and fractured (e.g., Wumishan Formation) reservoirs. It analyzes the relationships among market demand, policy regulation, and the dynamic characteristics of reservoir resources. The findings indicate: (1) Reduced consumption is the direct cause of the shift from declining to recovering water levels. Although porous and fractured reservoirs respond synchronously, their patterns differ. In porous reservoirs, abrupt shutdowns of unlicensed wells led to a sharp decline in non-reinjected extraction, causing water levels to transition from rapid decline to rapid and then slow recovery (a "V"-shaped response). In contrast, fractured reservoirs exhibited gradual consumption reduction due to sustained reinjection increases, resulting in a shift from slow decline to slow and then rapid recovery (a "U"-shaped response). (2) Hydrochemical components in both reservoirs remained stable, with no significant alteration to the subsurface chemical environment, though calcium carbonate scaling in some wells impaired reinjection efficiency. (3) Overly low reinjection temperatures in porous reservoirs risked cold front migration from injection wells, posing thermal breakthrough threats, whereas fractured reservoirs maintained stable temperatures—especially near deep conductive faults, demonstrating high exploitation potential due to deep heat sources. Tianjin’s large-scale reinjection practices hold significant implications for reestablishing thermal reservoir equilibrium, offering valuable insights for sustainable geothermal development in similar regions.
{"title":"Geothermal resource development and reservoir dynamics in Tianjin, China","authors":"Xiaoxiao Yin , Bowen Xu , Jian Shen , Zhenhai Zong , Guangyao Zhang , Zhilong Liu , Jinghong Hu","doi":"10.1016/j.geothermics.2025.103479","DOIUrl":"10.1016/j.geothermics.2025.103479","url":null,"abstract":"<div><div>Geothermal reservoir dynamic monitoring and research serve as the key scientific foundation for optimizing resource development, ensuring sustainable utilization, and mitigating exploitation risks. This paper systematically compiles nearly 50 years of geothermal utilization demand and management policies in Tianjin, along with data on application scenarios, extraction/injection volumes, thermal reservoir water levels, hydrochemical components, wellhead temperatures, and thermal reservoir temperatures for both porous (e.g., Guantao Formation) and fractured (e.g., Wumishan Formation) reservoirs. It analyzes the relationships among market demand, policy regulation, and the dynamic characteristics of reservoir resources. The findings indicate: (1) Reduced consumption is the direct cause of the shift from declining to recovering water levels. Although porous and fractured reservoirs respond synchronously, their patterns differ. In porous reservoirs, abrupt shutdowns of unlicensed wells led to a sharp decline in non-reinjected extraction, causing water levels to transition from rapid decline to rapid and then slow recovery (a \"V\"-shaped response). In contrast, fractured reservoirs exhibited gradual consumption reduction due to sustained reinjection increases, resulting in a shift from slow decline to slow and then rapid recovery (a \"U\"-shaped response). (2) Hydrochemical components in both reservoirs remained stable, with no significant alteration to the subsurface chemical environment, though calcium carbonate scaling in some wells impaired reinjection efficiency. (3) Overly low reinjection temperatures in porous reservoirs risked cold front migration from injection wells, posing thermal breakthrough threats, whereas fractured reservoirs maintained stable temperatures—especially near deep conductive faults, demonstrating high exploitation potential due to deep heat sources. Tianjin’s large-scale reinjection practices hold significant implications for reestablishing thermal reservoir equilibrium, offering valuable insights for sustainable geothermal development in similar regions.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103479"},"PeriodicalIF":3.9,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145121010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-21DOI: 10.1016/j.geothermics.2025.103491
Yi Yu , Hao Song , Jinlong Liang , Xuemin Liu , Zebin Luo , Jing Zhao , Zhipeng Li , Jinyong Xu
Earthquake forecasting remains challenging due to the limited understanding of reliable precursory signals. While hydrochemical anomalies in geothermal fluids prior to seismic events show promise, the response mechanism of H-O-C isotopes (δD, δ18O, δ13C) during seismogenesis and their quantitative links to tectonic processes are poorly constrained. We conducted continuous hydrogeochemical monitoring and stable isotope mass spectrometry (δD, δ18O, δ13CDIC) on geothermal fluids in the seismically active Xianshuihe fault zone (Western Sichuan, China). Time-series data from two hot springs (LTGS and EDQP) during the 2022∼2023 aftershock sequence of the Ms6.8 Luding earthquake were statistically analyzed using a Z-score method to quantify precursor anomalies. (1) Pre-seismic δD and δ18O exhibited rise-fall trends, driven by fracture-enhanced fluid mixing and water-rock interaction. δD anomalies were uniquely sensitive to earthquakes Ms ≥ 5.5. (2) Elevated δ13C originated from thermal decomposition of deep carbonate during tectonic stress accumulation, releasing 13C-enriched CO2. Subsequent dissolution and isotopic exchange impart this high-δ13C signature to dissolved inorganic carbon (DIC); (3) A Z-score ≥ 2 effectively discriminated precursor anomalies for Ms > 4.0 earthquakes, with precursor response times of 10 days to 2 months. This study establishes H-O-C isotopes as dynamic indicators of seismogenic processes and proposes a Z-score method for short-imminent earthquake forecasting. Integrating these indicators into multi-parameter monitoring networks, contributing to the development of multi-parameter seismic monitoring in active fault zones.
{"title":"The evidence of H-O-C isotopes in response to earthquake and the precursor anomaly index: A case study of geothermal fluids in the Xianshuihe fault","authors":"Yi Yu , Hao Song , Jinlong Liang , Xuemin Liu , Zebin Luo , Jing Zhao , Zhipeng Li , Jinyong Xu","doi":"10.1016/j.geothermics.2025.103491","DOIUrl":"10.1016/j.geothermics.2025.103491","url":null,"abstract":"<div><div>Earthquake forecasting remains challenging due to the limited understanding of reliable precursory signals. While hydrochemical anomalies in geothermal fluids prior to seismic events show promise, the response mechanism of H-O-C isotopes (δD, δ<sup>18</sup>O, δ<sup>13</sup>C) during seismogenesis and their quantitative links to tectonic processes are poorly constrained. We conducted continuous hydrogeochemical monitoring and stable isotope mass spectrometry (δD, δ<sup>18</sup>O, δ<sup>13</sup>C<sub>DIC</sub>) on geothermal fluids in the seismically active Xianshuihe fault zone (Western Sichuan, China). Time-series data from two hot springs (LTGS and EDQP) during the 2022∼2023 aftershock sequence of the <em>Ms</em>6.8 Luding earthquake were statistically analyzed using a <em>Z-score</em> method to quantify precursor anomalies. (1) Pre-seismic δD and δ<sup>18</sup>O exhibited rise-fall trends, driven by fracture-enhanced fluid mixing and water-rock interaction. δD anomalies were uniquely sensitive to earthquakes <em>Ms</em> ≥ 5.5. (2) Elevated δ<sup>13</sup>C originated from thermal decomposition of deep carbonate during tectonic stress accumulation, releasing <sup>13</sup>C-enriched CO<sub>2</sub>. Subsequent dissolution and isotopic exchange impart this high-δ<sup>13</sup>C signature to dissolved inorganic carbon (DIC); (3) A <em>Z-score</em> ≥ 2 effectively discriminated precursor anomalies for <em>Ms</em> > 4.0 earthquakes, with precursor response times of 10 days to 2 months. This study establishes H-O-C isotopes as dynamic indicators of seismogenic processes and proposes a <em>Z-score</em> method for short-imminent earthquake forecasting. Integrating these indicators into multi-parameter monitoring networks, contributing to the development of multi-parameter seismic monitoring in active fault zones.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103491"},"PeriodicalIF":3.9,"publicationDate":"2025-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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