Pub Date : 2026-01-01Epub 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":"2026-01-01","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 : 2026-01-01Epub 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":"2026-01-01","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 : 2026-01-01Epub 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":"2026-01-01","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}
Pub Date : 2026-01-01Epub Date: 2025-10-15DOI: 10.1016/j.geothermics.2025.103511
Yang Luo , Song Rao , Yizuo Shi , Xiaoqing Ren , Jin Na , Xiaorong Gao , Shengbiao Hu
The karst geothermal reservoir in northern China exhibits high vertical permeability and horizontal runoff conditions due to the development of cavities and fractures, resulting in large water yields and facilitating the reinjection of tailwater after geothermal utilization, thus offering significant development potential. In karst geothermal systems, fluid convection rapidly transfers heat, leading to pronounced local thermal anomalies. Consequently, quantitative evaluation of the heat accumulation effect of groundwater convection holds particular significance for understanding the genesis mechanisms of karst geothermal resources. The karst geothermal reservoir in the Jizhong Depression of the Bohai Bay Basin is well-developed, serving as a demonstration area for geothermal resource exploitation and utilization. Through coupled numerical simulations of the temperature field and hydrodynamic field, this paper focuses on the combined effects of forced and free convection in the karst geothermal reservoir of the Jizhong Depression and their heat accumulation effects. Additionally, it systematically investigates the impacts of the thickness, permeability of the karst geothermal reservoir, and fault zone width on the heat accumulation effect. Two-dimensional finite element numerical simulation results indicate that topography-driven fluids can promote the movement of convection cells, thereby enhancing the heat accumulation effect of groundwater convection. In karst geothermal systems, as the thickness, permeability of the karst geothermal reservoir, and fault width increase, the following outcomes are observed: enhanced cold water recharge upstream leads to a decrease in the average temperature of the karst geothermal reservoir; thermal plumes advance towards the downstream part of the basin; and the surface heat flux decreases upstream while increasing downstream, indicating an enhancement in the heat accumulation effect of groundwater convection activities.
{"title":"The heat accumulation effect enhanced by groundwater convection in Karst Geothermal Systems: a case study of karst geothermal reservoirs in the Jizhong Depression, Bohai Bay Basin, North China","authors":"Yang Luo , Song Rao , Yizuo Shi , Xiaoqing Ren , Jin Na , Xiaorong Gao , Shengbiao Hu","doi":"10.1016/j.geothermics.2025.103511","DOIUrl":"10.1016/j.geothermics.2025.103511","url":null,"abstract":"<div><div>The karst geothermal reservoir in northern China exhibits high vertical permeability and horizontal runoff conditions due to the development of cavities and fractures, resulting in large water yields and facilitating the reinjection of tailwater after geothermal utilization, thus offering significant development potential. In karst geothermal systems, fluid convection rapidly transfers heat, leading to pronounced local thermal anomalies. Consequently, quantitative evaluation of the heat accumulation effect of groundwater convection holds particular significance for understanding the genesis mechanisms of karst geothermal resources. The karst geothermal reservoir in the Jizhong Depression of the Bohai Bay Basin is well-developed, serving as a demonstration area for geothermal resource exploitation and utilization. Through coupled numerical simulations of the temperature field and hydrodynamic field, this paper focuses on the combined effects of forced and free convection in the karst geothermal reservoir of the Jizhong Depression and their heat accumulation effects. Additionally, it systematically investigates the impacts of the thickness, permeability of the karst geothermal reservoir, and fault zone width on the heat accumulation effect. Two-dimensional finite element numerical simulation results indicate that topography-driven fluids can promote the movement of convection cells, thereby enhancing the heat accumulation effect of groundwater convection. In karst geothermal systems, as the thickness, permeability of the karst geothermal reservoir, and fault width increase, the following outcomes are observed: enhanced cold water recharge upstream leads to a decrease in the average temperature of the karst geothermal reservoir; thermal plumes advance towards the downstream part of the basin; and the surface heat flux decreases upstream while increasing downstream, indicating an enhancement in the heat accumulation effect of groundwater convection activities.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103511"},"PeriodicalIF":3.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145332988","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 : 2026-01-01Epub Date: 2025-10-24DOI: 10.1016/j.geothermics.2025.103512
Oksana V. Lunina, Ivan A. Denisenko, Anton A. Gladkov
The current study aimed to identify possible prerequisites for the discovery of deep thermal waters along the southern shore of Baikal Lake between the villages of Mangutai and Solzan. The results of morphotectonic and structural mapping during the present investigation revealed that the NW-SE trending South Baikal, Utulik, and Coastal faults, particularly in their junctions with the NE-SW and NNE-SSW trending faults, are the most favorable for groundwater discharge. The infrared unmanned aerial vehicle survey carried out along the coastal strip for 37 km at night, discovered several anomalies. For this purpose, anomalies associated with green vegetation, locations where rivers enter Lake Baikal, areas where warm water flows from natural coastal water reservoirs, and anomalies generated by industrial activity were excluded. Finally, increased fracture density at m2 and m3 units, permeable faults, and the most apparent thermal anomalies indicated the most promising locations for further investigation. The anomaly close to the village of Utulik, where hot water may contain sufficient radon for therapeutic purposes, was defined as a priority. The overall results, as well as the structural and lithological similarity between the research area and other promising sites on the eastern coast of Lake Baikal, point to the presence of a geothermal reservoir at depth in the sediments of the Utulik-Solzan depression and the adjacent part of Lake Baikal. Other research are required to appraise geothermal resources and make judgments about future searches for thermal waters.
{"title":"Using fault mapping and infrared UAV survey for thermal water prospection along the southern shore of Lake Baikal: a case study","authors":"Oksana V. Lunina, Ivan A. Denisenko, Anton A. Gladkov","doi":"10.1016/j.geothermics.2025.103512","DOIUrl":"10.1016/j.geothermics.2025.103512","url":null,"abstract":"<div><div>The current study aimed to identify possible prerequisites for the discovery of deep thermal waters along the southern shore of Baikal Lake between the villages of Mangutai and Solzan. The results of morphotectonic and structural mapping during the present investigation revealed that the NW-SE trending South Baikal, Utulik, and Coastal faults, particularly in their junctions with the NE-SW and NNE-SSW trending faults, are the most favorable for groundwater discharge. The infrared unmanned aerial vehicle survey carried out along the coastal strip for 37 km at night, discovered several anomalies. For this purpose, anomalies associated with green vegetation, locations where rivers enter Lake Baikal, areas where warm water flows from natural coastal water reservoirs, and anomalies generated by industrial activity were excluded. Finally, increased fracture density at m<sup>2</sup> and m<sup>3</sup> units, permeable faults, and the most apparent thermal anomalies indicated the most promising locations for further investigation. The anomaly close to the village of Utulik, where hot water may contain sufficient radon for therapeutic purposes, was defined as a priority. The overall results, as well as the structural and lithological similarity between the research area and other promising sites on the eastern coast of Lake Baikal, point to the presence of a geothermal reservoir at depth in the sediments of the Utulik-Solzan depression and the adjacent part of Lake Baikal. Other research are required to appraise geothermal resources and make judgments about future searches for thermal waters.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103512"},"PeriodicalIF":3.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145363535","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}
Hot springs with radiogenic activity and high lithium enrichment has an important role in storing energy extracted from geothermal water. In Bangka Island, Indonesia, there are hot springs that appear in non-volcanic areas with high radiogenic activity and lithium enrichment. However, the origin of radiogenic hot springs in these non-volcanic areas is still not well understood. Geochemical analysis, especially of lithium in geothermal systems, provides important insights into geochemical processes occurring in the Earth's lithosphere. This study explores the mechanism of lithium enrichment in radiogenic hot springs on Bangka Island with a focus on the influence of water-rock interactions. Water samples from six hot springs were analysed for physical parameters, cations, and anions. The results show that the hot springs are classified into three categories; geothermal hot spring water systems with a predominance of sodium-carbonate water (Pemali, Terak, Keretak, and Nyelanding), where lithium enrichment comes from lithospheric water due to the interaction between water and rock, with a high contribution of meteoric water; a geothermal water system with a predominance of sodium chloride water (Dendang) and a geothermal water system with a predominance of sodium chloride water (Permis), where the high lithium enrichment comes from lithospheric water due to the interaction between water and rock, with the influence of seawater. The difference between the calculated and observed magnesium (Mg) concentrations indicates a mixing process prior to heating between meteoric water and seawater. The reservoir temperatures were estimated by quartz geothermometer (63 - 89 °C) as the shallow reservoir mixed with cold meteoric water and multicomponent geothermometer (88 - 111 °C) as the deep reservoir. Our findings reveal that the correlation results between geochemical analysis and geothermometer analysis confirms that Dendang (DND) hot springs originate from older hydrothermal reservoirs with lithospheric water enriched in lithium through water-rock interactions. In contrast, Permis (PMS) hot spring is influenced by shallow aquifers with seawater intrusion, heated by reservoirs at minimal depths, contributing to lithium enrichment. Variations in elevation, proximity to the coast, and geographic factors further shape these systems, with other hot springs in Bangka Island primarily sourced from radiogenically heated shallow groundwater. These findings highlight the potential of radiogenic hot springs in non-volcanic regions as unconventional sources of lithium, contributing to the development of energy storage solutions and advancing geothermal resource utilization.
{"title":"Lithium enrichment in high radiogenic geothermal systems originating from lithospheric water due to water-rock interactions","authors":"Rahmat Nawi Siregar , Sismanto Sismanto , Kuwat Triyana , Agung Harijoko , Mochamad Iqbal , Ganesha Antarnusa , Fredi Ganda Putra , Rofiqul Umam","doi":"10.1016/j.geothermics.2025.103499","DOIUrl":"10.1016/j.geothermics.2025.103499","url":null,"abstract":"<div><div>Hot springs with radiogenic activity and high lithium enrichment has an important role in storing energy extracted from geothermal water. In Bangka Island, Indonesia, there are hot springs that appear in non-volcanic areas with high radiogenic activity and lithium enrichment. However, the origin of radiogenic hot springs in these non-volcanic areas is still not well understood. Geochemical analysis, especially of lithium in geothermal systems, provides important insights into geochemical processes occurring in the Earth's lithosphere. This study explores the mechanism of lithium enrichment in radiogenic hot springs on Bangka Island with a focus on the influence of water-rock interactions. Water samples from six hot springs were analysed for physical parameters, cations, and anions. The results show that the hot springs are classified into three categories; geothermal hot spring water systems with a predominance of sodium-carbonate water (Pemali, Terak, Keretak, and Nyelanding), where lithium enrichment comes from lithospheric water due to the interaction between water and rock, with a high contribution of meteoric water; a geothermal water system with a predominance of sodium chloride water (Dendang) and a geothermal water system with a predominance of sodium chloride water (Permis), where the high lithium enrichment comes from lithospheric water due to the interaction between water and rock, with the influence of seawater. The difference between the calculated and observed magnesium (Mg) concentrations indicates a mixing process prior to heating between meteoric water and seawater. The reservoir temperatures were estimated by quartz geothermometer (63 - 89 °C) as the shallow reservoir mixed with cold meteoric water and multicomponent geothermometer (88 - 111 °C) as the deep reservoir. Our findings reveal that the correlation results between geochemical analysis and geothermometer analysis confirms that Dendang (DND) hot springs originate from older hydrothermal reservoirs with lithospheric water enriched in lithium through water-rock interactions. In contrast, Permis (PMS) hot spring is influenced by shallow aquifers with seawater intrusion, heated by reservoirs at minimal depths, contributing to lithium enrichment. Variations in elevation, proximity to the coast, and geographic factors further shape these systems, with other hot springs in Bangka Island primarily sourced from radiogenically heated shallow groundwater. These findings highlight the potential of radiogenic hot springs in non-volcanic regions as unconventional sources of lithium, contributing to the development of energy storage solutions and advancing geothermal resource utilization.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103499"},"PeriodicalIF":3.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107950","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 : 2026-01-01Epub Date: 2025-11-06DOI: 10.1016/j.geothermics.2025.103521
Siming Dong , Chenglong Wang , Hanlong Liu , Abdelmalek Bouazza , Xuanming Ding , Gangqiang Kong
This study proposes a hybrid framework that combines interpretable machine learning, multi-physical field simulation, and Bayesian optimization to address the challenges posed by diverse structural and geological conditions, as well as the lack of interpretability in predicting the heat transfer performance of energy pipe piles. A three-dimensional transient heat transfer numerical model was used to generate a comprehensive dataset. This dataset includes variations in key heat transfer parameters (pipe pile structure, fluid parameters, and material thermal properties). A backpropagation neural network (BPNN) was used for prediction, with the impact of various hyperparameters analyzed. Model performance was significantly improved through Bayesian optimization, which automatically identified the most suitable hyperparameter combinations. To improve interpretability, the SHAP (Shapley additive explanations) method was used to quantify the contribution of each input feature to the model’s output. Among all features, the inlet water temperature had the highest influence, accounting for 23.4 % of the prediction. SHAP also provided insights into how each feature affects the model’s decision-making process.
{"title":"A machine learning hybrid model for heat transfer per meter prediction of energy pipe pile","authors":"Siming Dong , Chenglong Wang , Hanlong Liu , Abdelmalek Bouazza , Xuanming Ding , Gangqiang Kong","doi":"10.1016/j.geothermics.2025.103521","DOIUrl":"10.1016/j.geothermics.2025.103521","url":null,"abstract":"<div><div>This study proposes a hybrid framework that combines interpretable machine learning, multi-physical field simulation, and Bayesian optimization to address the challenges posed by diverse structural and geological conditions, as well as the lack of interpretability in predicting the heat transfer performance of energy pipe piles. A three-dimensional transient heat transfer numerical model was used to generate a comprehensive dataset. This dataset includes variations in key heat transfer parameters (pipe pile structure, fluid parameters, and material thermal properties). A backpropagation neural network (BPNN) was used for prediction, with the impact of various hyperparameters analyzed. Model performance was significantly improved through Bayesian optimization, which automatically identified the most suitable hyperparameter combinations. To improve interpretability, the SHAP (Shapley additive explanations) method was used to quantify the contribution of each input feature to the model’s output. Among all features, the inlet water temperature had the highest influence, accounting for 23.4 % of the prediction. SHAP also provided insights into how each feature affects the model’s decision-making process.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103521"},"PeriodicalIF":3.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474469","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 : 2026-01-01Epub Date: 2025-10-31DOI: 10.1016/j.geothermics.2025.103516
Lu Ge, Hongbin Tan, Fei Xue
Hot springs in the southern Tibetan Plateau exhibit abnormally high concentrations of arsenic (As). However, the mechanisms responsible for As enrichment are still under debate. Rare earth elements (REE), which serve as effective tracers of water-rock interactions in geothermal systems, provide valuable insights into identifying As sources and enrichment processes. In this study, two representative hot spring systems were investigated: Buxionglanggu (BXLG), a magmatic geothermal system, and Quzhuomu (QZM), a non-magmatic geothermal system. The geochemical characteristics of REE in the hot springs are analyzed to determine their distribution and fractionation patterns, and to explore their indications for As enrichment. Fe oxides/hydroxides play a dominant role in controlling REE concentrations. Calculations of REE complexes show that carbonate complexes dominate in samples with pH values of 7–8 and water temperatures below 70 °C, whereas oxyhydroxide complexes prevail at pH ≥ 8 and temperatures > 70 °C. Chondrite-normalized REE patterns display differences between the two systems: BXLG shows enrichment in LREE and HREE, while QZM displays varying degrees of LREE enrichment. REE fractionation is influenced by multiple geochemical processes: (1) During water-rock interaction, HREE and MREE are preferentially leached from host rocks, resulting in a leftward tilt in the REE pattern observed in BXLG hot springs compared to their host rocks, whereas QZM hot springs largely preserve the REE signature of the source rocks; (2) Adsorption and desorption processes mediated by Fe oxide/hydroxide colloids play a significant role in REE fractionation, as evidenced by the strong positive correlation between LREE and Fe concentrations; (3) pH and temperature collectively influence the distribution and fractionation of REE complexes in hot spring waters. Notably, the As concentrations (average 953.2 µg/L) and As/ΣREE values (average 11,717) in the BXLG hot springs are significantly higher than those in the QZM hot springs (mean As concentrations of 49.6 µg/L and mean As/ΣREE of 782). These significant differences between the two hot spring systems suggest distinct sources of As. In the QZM hot springs, As is primarily derived from water-rock interactions, whereas magmatic fluids are predominantly responsible for As enrichment in the BXLG hot springs. Moreover, positive Ce and Eu anomalies may serve as potential geochemical indicators of As enrichment, with higher Eu/Eu* values correlating with elevated As concentrations.
{"title":"Geochemical behavior of rare earth elements in high-arsenic hot springs in southern Tibet (China): New findings on arsenic enrichment","authors":"Lu Ge, Hongbin Tan, Fei Xue","doi":"10.1016/j.geothermics.2025.103516","DOIUrl":"10.1016/j.geothermics.2025.103516","url":null,"abstract":"<div><div>Hot springs in the southern Tibetan Plateau exhibit abnormally high concentrations of arsenic (As). However, the mechanisms responsible for As enrichment are still under debate. Rare earth elements (REE), which serve as effective tracers of water-rock interactions in geothermal systems, provide valuable insights into identifying As sources and enrichment processes. In this study, two representative hot spring systems were investigated: Buxionglanggu (BXLG), a magmatic geothermal system, and Quzhuomu (QZM), a non-magmatic geothermal system. The geochemical characteristics of REE in the hot springs are analyzed to determine their distribution and fractionation patterns, and to explore their indications for As enrichment. Fe oxides/hydroxides play a dominant role in controlling REE concentrations. Calculations of REE complexes show that carbonate complexes dominate in samples with pH values of 7–8 and water temperatures below 70 °C, whereas oxyhydroxide complexes prevail at pH ≥ 8 and temperatures > 70 °C. Chondrite-normalized REE patterns display differences between the two systems: BXLG shows enrichment in LREE and HREE, while QZM displays varying degrees of LREE enrichment. REE fractionation is influenced by multiple geochemical processes: (1) During water-rock interaction, HREE and MREE are preferentially leached from host rocks, resulting in a leftward tilt in the REE pattern observed in BXLG hot springs compared to their host rocks, whereas QZM hot springs largely preserve the REE signature of the source rocks; (2) Adsorption and desorption processes mediated by Fe oxide/hydroxide colloids play a significant role in REE fractionation, as evidenced by the strong positive correlation between LREE and Fe concentrations; (3) pH and temperature collectively influence the distribution and fractionation of REE complexes in hot spring waters. Notably, the As concentrations (average 953.2 µg/L) and As/ΣREE values (average 11,717) in the BXLG hot springs are significantly higher than those in the QZM hot springs (mean As concentrations of 49.6 µg/L and mean As/ΣREE of 782). These significant differences between the two hot spring systems suggest distinct sources of As. In the QZM hot springs, As is primarily derived from water-rock interactions, whereas magmatic fluids are predominantly responsible for As enrichment in the BXLG hot springs. Moreover, positive Ce and Eu anomalies may serve as potential geochemical indicators of As enrichment, with higher Eu/Eu* values correlating with elevated As concentrations.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103516"},"PeriodicalIF":3.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145424347","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 : 2026-01-01Epub Date: 2025-10-30DOI: 10.1016/j.geothermics.2025.103514
Peter Birkle , Philip J. Ball
For the first time in the Red Sea region, sub-salt aquifers from the northern part of the deep proximal rift basin were assessed on the provenance of formation water, flow dynamics, and hydrothermal alteration processes. Five preserved bottomhole water samples were recovered from Upper Cretaceous and Lower Miocene sedimentary units from three offshore exploratory wells, analyzed on their hydrochemical (major elements, trace elements) and multi-isotopic composition (δ2H, δ11B, δ13C, 14C, δ18O, δ37Cl, δ81Br, 87Sr/86Sr), and compared with different brine manifestations in the Middle East. NaCl type, brackish water (Red Sea Low Salinity Water, RS-LS) infiltrated nearby the Red Sea coastal area. Toward the interior part of the Red Sea basin, seawater evaporation in a sabkha-type surface environment preceded the infiltration of Na-Ca-Cl type, hypersaline Red Sea Formation Brine (RS-FB) with a mineralization of up to 348,000 mg/l, likely triggered by a global sea-level drop during Last Glacial Maximum. 14C concentrations from 3.73 ± 0.06 to 10.1 ± 0.14 pMC (percent Modern Carbon) for RS-FB and 2.12 ± 0.04 to 13.3 ± 0.1 pMC for RS-LS reveal a residence time of 17,998 ± 60 - 32,735 ± 150 yr BP (years Before Present) for the Red Sea basin aquifer systems. The infiltration of surface water occurred through vertical flow pathways along normal fault planes of hanging-walls. Overlapping carbon-14 ages for aquifers from the Red Sea Basin and the Upper Mega Aquifer System on the Arabian Platform suggest a common recharge event during Late Pleistocene period on the Arabian Peninsula under humid paleo-climatic conditions. Distinct 87Sr/86Sr ratios between RS-FB (0.707307 - 0.707350) and Mid-Miocene evaporites (0.70890 - 0.70898) exclude secondary dissolution of halite as feasible brine-forming mechanism for the studied sub-salt units. Intermediate 87Sr/86Sr signatures of RS-FB fluids (87Sr/86Sr = 0.707307 – 0.707350) between present seawater (0.7092) and Rea Sea volcanic basement (0.70269 - 0.70315), plus the presence of partially albitized feldspar and kaolinite in basement basalts, suggest a deep-circulating, active hydrothermal convective system with a calculated strontium contribution of 29% from 87Sr/86Sr -depleted basalts. A positive 18O shift (δ18O up to +6.4‰) reflects the occurrence of secondary hydrothermal water rock interaction processes. δ37Cl ratios between -0.23‰ ± 0.11 and 0.18‰ ± 0.09 indicate dynamic groundwater flow, contrasting to generally 37Cl-depleted static sedimentary pore fluids. δ11B values from 17.2 to 28.2‰ point to clay desorption as mechanism to accumulate kaolinite and illite in the Miocene and Cretaceous aquifer strata.
{"title":"Geochemical evidence for fluid provenance and hydrothermal alteration processes in sub-salt units of the Northern Red Sea","authors":"Peter Birkle , Philip J. Ball","doi":"10.1016/j.geothermics.2025.103514","DOIUrl":"10.1016/j.geothermics.2025.103514","url":null,"abstract":"<div><div>For the first time in the Red Sea region, sub-salt aquifers from the northern part of the deep proximal rift basin were assessed on the provenance of formation water, flow dynamics, and hydrothermal alteration processes. Five preserved bottomhole water samples were recovered from Upper Cretaceous and Lower Miocene sedimentary units from three offshore exploratory wells, analyzed on their hydrochemical (major elements, trace elements) and multi-isotopic composition (δ<sup>2</sup>H, δ<sup>11</sup>B, δ<sup>13</sup>C, <sup>14</sup>C, δ<sup>18</sup>O, δ<sup>37</sup>Cl, δ<sup>81</sup>Br, <sup>87</sup>Sr/<sup>86</sup>Sr), and compared with different brine manifestations in the Middle East. NaCl type, brackish water (Red Sea Low Salinity Water, RS-LS) infiltrated nearby the Red Sea coastal area. Toward the interior part of the Red Sea basin, seawater evaporation in a sabkha-type surface environment preceded the infiltration of Na-Ca-Cl type, hypersaline Red Sea Formation Brine (RS-FB) with a mineralization of up to 348,000 mg/l, likely triggered by a global sea-level drop during Last Glacial Maximum. <sup>14</sup>C concentrations from 3.73 ± 0.06 to 10.1 ± 0.14 pMC (percent Modern Carbon) for RS-FB and 2.12 ± 0.04 to 13.3 ± 0.1 pMC for RS-LS reveal a residence time of 17,998 ± 60 - 32,735 ± 150 yr BP (years Before Present) for the Red Sea basin aquifer systems. The infiltration of surface water occurred through vertical flow pathways along normal fault planes of hanging-walls. Overlapping carbon-14 ages for aquifers from the Red Sea Basin and the Upper Mega Aquifer System on the Arabian Platform suggest a common recharge event during Late Pleistocene period on the Arabian Peninsula under humid paleo-climatic conditions. Distinct <sup>87</sup>Sr/<sup>86</sup>Sr ratios between RS-FB (0.707307 - 0.707350) and Mid-Miocene evaporites (0.70890 - 0.70898) exclude secondary dissolution of halite as feasible brine-forming mechanism for the studied sub-salt units. Intermediate <sup>87</sup>Sr/<sup>86</sup>Sr signatures of RS-FB fluids (<sup>87</sup>Sr/<sup>86</sup>Sr = 0.707307 – 0.707350) between present seawater (0.7092) and Rea Sea volcanic basement (0.70269 - 0.70315), plus the presence of partially albitized feldspar and kaolinite in basement basalts, suggest a deep-circulating, active hydrothermal convective system with a calculated strontium contribution of 29% from <sup>87</sup>Sr/<sup>86</sup>Sr -depleted basalts. A positive <sup>18</sup>O shift (δ<sup>18</sup>O up to +6.4‰) reflects the occurrence of secondary hydrothermal water rock interaction processes. δ<sup>37</sup>Cl ratios between -0.23‰ ± 0.11 and 0.18‰ ± 0.09 indicate dynamic groundwater flow, contrasting to generally <sup>37</sup>Cl-depleted static sedimentary pore fluids. δ<sup>11</sup>B values from 17.2 to 28.2‰ point to clay desorption as mechanism to accumulate kaolinite and illite in the Miocene and Cretaceous aquifer strata.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103514"},"PeriodicalIF":3.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145424348","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 : 2026-01-01Epub Date: 2025-10-16DOI: 10.1016/j.geothermics.2025.103509
Mohammad J.A. Moein , Cornelius Langenbruch , Serge Shapiro
Developing geoenergy technologies such as Enhanced Geothermal Systems (EGS) requires underground fluid injection operations, which, under certain conditions, can induce large-magnitude earthquakes. To mitigate the seismic hazard, various injection protocols have been proposed to regulate operational parameters. This study evaluates the impact of injection protocol on induced seismic hazard, using theoretical models, numerical simulations and field data. Within the theoretical framework, perturbed rock volume was inferred from the concept of triggering front that serves as a proxy for pressure perturbation, whereas numerical modeling captured the spatio-temporal evolution of pore-pressure. Our results indicate that short-duration injection protocols are likely characterized by lower seismic hazard, as they perturb smaller areas of pre-existing critically stressed faults. This decreases the likelihood of larger ruptures, that might propagate beyond the pressurized rock volume. Given the same (net) injected fluid volumes and geological conditions, the duration emerges as a key factor controlling the extent of the perturbed rock mass. The findings are further illustrated by the 2017 5.4 Pohang earthquake, which was triggered by the hydraulic stimulation of the nearby EGS. Previously in 2006, the injection of roughly similar fluid volume in Basel induced an earthquake of magnitude 3.4. This difference in energy release is likely linked to the duration of the injection protocols, being approximately 600 days at Pohang and 6 days at Basel. Our findings highlight the importance of injection protocol, detailed subsurface characterization and real-time seismic monitoring of perturbed rock volumes to mitigate the seismic hazard during EGS developments.
{"title":"Understanding the impact of injection duration on the induced seismic hazard","authors":"Mohammad J.A. Moein , Cornelius Langenbruch , Serge Shapiro","doi":"10.1016/j.geothermics.2025.103509","DOIUrl":"10.1016/j.geothermics.2025.103509","url":null,"abstract":"<div><div>Developing geoenergy technologies such as Enhanced Geothermal Systems (EGS) requires underground fluid injection operations, which, under certain conditions, can induce large-magnitude earthquakes. To mitigate the seismic hazard, various injection protocols have been proposed to regulate operational parameters. This study evaluates the impact of injection protocol on induced seismic hazard, using theoretical models, numerical simulations and field data. Within the theoretical framework, perturbed rock volume was inferred from the concept of triggering front that serves as a proxy for pressure perturbation, whereas numerical modeling captured the spatio-temporal evolution of pore-pressure. Our results indicate that short-duration injection protocols are likely characterized by lower seismic hazard, as they perturb smaller areas of pre-existing critically stressed faults. This decreases the likelihood of larger ruptures, that might propagate beyond the pressurized rock volume. Given the same (net) injected fluid volumes and geological conditions, the duration emerges as a key factor controlling the extent of the perturbed rock mass. The findings are further illustrated by the 2017 <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>L</mi></mrow></msub></math></span> 5.4 Pohang earthquake, which was triggered by the hydraulic stimulation of the nearby EGS. Previously in 2006, the injection of roughly similar fluid volume in Basel induced an earthquake of magnitude <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>L</mi></mrow></msub></math></span> 3.4. This difference in energy release is likely linked to the duration of the injection protocols, being approximately 600 days at Pohang and 6 days at Basel. Our findings highlight the importance of injection protocol, detailed subsurface characterization and real-time seismic monitoring of perturbed rock volumes to mitigate the seismic hazard during EGS developments.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"134 ","pages":"Article 103509"},"PeriodicalIF":3.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145332989","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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