The exploitation and utilization of geothermal energy necessitate a clear understanding of the genesis mechanisms of geothermal systems. The complex geological conditions result in diverse hydrochemical characteristics of enriched geothermal waters in the Gaoligong geothermal belt, southeastern Tibetan Plateau. This study employs the Self-Organizing Map (SOM) and Positive Matrix Factorization (PMF) algorithms, along with hydrochemical and hydrogen-oxygen isotope analyses, to identify the genesis mechanisms among different types of geothermal waters. Three types of geothermal water were identified in the study area (Groups 1 − 3). For Group 1, the contribution ratio of carbonate mineral dissolution (calcite, dolomite) is 37.6 %, followed by evaporite minerals (gypsum: 17.2 %, halite: 16.6 %) and silicates (28.6 %). In Group 2, silicate minerals (Ca- and Mg-rich silicates: 41.5 %, Na-rich silicates: 30.1 %) contribute the most to the components, followed by pyrite (28.4 %). For Group 3, the components are primarily derived from silicate dissolution (sandstone: 18.0 %, granite: 31.2 %), followed by geothermal gases (25.7 %) and carbonates (25.1 %). The geothermal reservoir temperatures of Groups 1 to 3 before and after mixing are 111 °C to 61 °C, 170 °C to 78 °C, and 124 °C to 63 °C, respectively. This study identified the recharge sources, quantified the sources of the major components, and assessed the reservoir temperature. Based on these findings, the corresponding genesis mechanisms with different hydrochemical characteristics were established. This study aims to deepen the understanding of magma chamber-driven geothermal systems and provide valuable support for the development and utilization of geothermal resources worldwide.
{"title":"Hydrochemical fingerprints, source apportionment and genesis mechanism of geothermal waters in the Gaoligong Geothermal Belt, southeastern Tibetan Plateau","authors":"Jinhang Huang , Xingze Li , Xingwang Chang , Xingcheng Yuan , Xun Huang , Hongyang Guo , Yunhui Zhang","doi":"10.1016/j.geothermics.2025.103577","DOIUrl":"10.1016/j.geothermics.2025.103577","url":null,"abstract":"<div><div>The exploitation and utilization of geothermal energy necessitate a clear understanding of the genesis mechanisms of geothermal systems. The complex geological conditions result in diverse hydrochemical characteristics of enriched geothermal waters in the Gaoligong geothermal belt, southeastern Tibetan Plateau. This study employs the Self-Organizing Map (SOM) and Positive Matrix Factorization (PMF) algorithms, along with hydrochemical and hydrogen-oxygen isotope analyses, to identify the genesis mechanisms among different types of geothermal waters. Three types of geothermal water were identified in the study area (Groups 1 − 3). For Group 1, the contribution ratio of carbonate mineral dissolution (calcite, dolomite) is 37.6 %, followed by evaporite minerals (gypsum: 17.2 %, halite: 16.6 %) and silicates (28.6 %). In Group 2, silicate minerals (Ca- and Mg-rich silicates: 41.5 %, Na-rich silicates: 30.1 %) contribute the most to the components, followed by pyrite (28.4 %). For Group 3, the components are primarily derived from silicate dissolution (sandstone: 18.0 %, granite: 31.2 %), followed by geothermal gases (25.7 %) and carbonates (25.1 %). The geothermal reservoir temperatures of Groups 1 to 3 before and after mixing are 111 °C to 61 °C, 170 °C to 78 °C, and 124 °C to 63 °C, respectively. This study identified the recharge sources, quantified the sources of the major components, and assessed the reservoir temperature. Based on these findings, the corresponding genesis mechanisms with different hydrochemical characteristics were established. This study aims to deepen the understanding of magma chamber-driven geothermal systems and provide valuable support for the development and utilization of geothermal resources worldwide.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103577"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925312","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 : 2026-03-01Epub Date: 2026-01-05DOI: 10.1016/j.geothermics.2025.103593
Suzan Pasvanoğlu , Serkan Vural , Tekin Yeken
<div><div>The Kepekler-Ilıcaboğazı geothermal field is located in northwest Anatolia, within Balıkesir Province, and comprises both thermal waters and therapeutic clay mud (Peloids). The thermal waters emerge as springs with a temperature range from 30 to 56 °C, with discharge rates of 0.01−4 L/s along a secondary fault in the North Anatolian Fault Zone (NAFZ). Only one (BK-1) production well was drilled to a depth of 390.30 m by General Directorate of Mineral Research and Exploration of Türkiye (MTA), which has a water temperature of 64 °C and a discharge rate of 15 L/<em>sec</em>. This study investigates the chemical and isotopic characteristics of thermal and cold waters using the major ion and trace element contents as well as environmental isotope compositions. The thermal waters belong to the alkaline NaCl-type, and are characterized by pH values of 6.35 and 7.90, generally higher EC (3149–3856 µS/cm), and relatively high concentrations of Cl, Na, B, As, Rb, Li, Cs, and Sr, in contrast to the cold waters, which are primarily of the CaHCO<sub>3</sub> type. Carbonate and silicate dissolution, ion exchange, and energy loss through heat conduction are processes responsible for the origin and evolution of NaCl-type water. Thermal waters tend to have lower B/Cl ratios and strong correlations between (Cl and B, Li, and Rb) trace alkali metals and Cl due to rapid, efficient upflow pathways. These features align with high vertical permeability networks that promote efficient upflow and meteoric mixing, delineating the systems of the Kepekler-Ilıcaboğazı area. By estimating reservoir temperatures using chemical geothermometers and saturation indices, reservoir temperature estimates (75–100 °C) may be affected by conductive cooling, mixing, or partial equilibration—especially as most waters plot as "immature" on Giggenbach diagrams. Chemical equilibrium studies show that the thermal waters are in equilibrium with respect to calcite, aragonite, and quartz, while undersaturated with respect to albite, anorthite, K-feldspar, and gypsum. Thermal waters are meteoric in origin as suggested by the isotope (δ<sup>18</sup>O, δ<sup>2</sup>H, <sup>3</sup>H) composition. Carbon in thermal waters is likely to originate from metamorphic CO<sub>2</sub> or marine carbonates whereas carbon in cold waters is derived from an organic source. δ<sup>34</sup>S sulfur is derived from bacterial sulfate reduction and the dissolution of marine carbonates and sulfide minerals. The study area features a fault-controlled convection deep circulation geothermal system. Thermal waters are sourced from a resource base in the upper crust, which consists of thick granitic and metamorphic rocks that reach the surface. Using the results of hydrogeology and hydrogeochemistry, a conceptual hydrothermal model of recharge, mixing, and discharge has been proposed for the formation of the thermal waters in the study area. This is the first comprehensive geochemical and isotope-based investigati
{"title":"Geochemistry and genesis analysis of the Kepekler – Ilıcaboğazı thermal waters (Balıkesir, NW Türkiye)","authors":"Suzan Pasvanoğlu , Serkan Vural , Tekin Yeken","doi":"10.1016/j.geothermics.2025.103593","DOIUrl":"10.1016/j.geothermics.2025.103593","url":null,"abstract":"<div><div>The Kepekler-Ilıcaboğazı geothermal field is located in northwest Anatolia, within Balıkesir Province, and comprises both thermal waters and therapeutic clay mud (Peloids). The thermal waters emerge as springs with a temperature range from 30 to 56 °C, with discharge rates of 0.01−4 L/s along a secondary fault in the North Anatolian Fault Zone (NAFZ). Only one (BK-1) production well was drilled to a depth of 390.30 m by General Directorate of Mineral Research and Exploration of Türkiye (MTA), which has a water temperature of 64 °C and a discharge rate of 15 L/<em>sec</em>. This study investigates the chemical and isotopic characteristics of thermal and cold waters using the major ion and trace element contents as well as environmental isotope compositions. The thermal waters belong to the alkaline NaCl-type, and are characterized by pH values of 6.35 and 7.90, generally higher EC (3149–3856 µS/cm), and relatively high concentrations of Cl, Na, B, As, Rb, Li, Cs, and Sr, in contrast to the cold waters, which are primarily of the CaHCO<sub>3</sub> type. Carbonate and silicate dissolution, ion exchange, and energy loss through heat conduction are processes responsible for the origin and evolution of NaCl-type water. Thermal waters tend to have lower B/Cl ratios and strong correlations between (Cl and B, Li, and Rb) trace alkali metals and Cl due to rapid, efficient upflow pathways. These features align with high vertical permeability networks that promote efficient upflow and meteoric mixing, delineating the systems of the Kepekler-Ilıcaboğazı area. By estimating reservoir temperatures using chemical geothermometers and saturation indices, reservoir temperature estimates (75–100 °C) may be affected by conductive cooling, mixing, or partial equilibration—especially as most waters plot as \"immature\" on Giggenbach diagrams. Chemical equilibrium studies show that the thermal waters are in equilibrium with respect to calcite, aragonite, and quartz, while undersaturated with respect to albite, anorthite, K-feldspar, and gypsum. Thermal waters are meteoric in origin as suggested by the isotope (δ<sup>18</sup>O, δ<sup>2</sup>H, <sup>3</sup>H) composition. Carbon in thermal waters is likely to originate from metamorphic CO<sub>2</sub> or marine carbonates whereas carbon in cold waters is derived from an organic source. δ<sup>34</sup>S sulfur is derived from bacterial sulfate reduction and the dissolution of marine carbonates and sulfide minerals. The study area features a fault-controlled convection deep circulation geothermal system. Thermal waters are sourced from a resource base in the upper crust, which consists of thick granitic and metamorphic rocks that reach the surface. Using the results of hydrogeology and hydrogeochemistry, a conceptual hydrothermal model of recharge, mixing, and discharge has been proposed for the formation of the thermal waters in the study area. This is the first comprehensive geochemical and isotope-based investigati","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103593"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925313","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 : 2026-03-01Epub Date: 2026-01-22DOI: 10.1016/j.geothermics.2026.103606
M. Lelli , E. Dallara , L. Marini , G. Bini
Although carbonyl sulfide (COS) has long been recognized as a potentially valuable geothermometric indicator, its use has been limited by the scarcity of analytical data, mainly due to instrumental limitations in the 1990s. In this work, new geothermometric functions and graphical tools were developed for the H2O–CO2–H2S–H2–CH4–CO–COS system and applied to new data of Larderello (Italy) and Krafla (Iceland) geothermal fluids. Thermodynamic data of COS and other gas species were re-evaluated, vapor–liquid distribution coefficients were extrapolated, and the gas equilibria were formulated for different aquifer conditions: saturated pure liquid water, two-phase liquid plus vapor mixtures produced by addition of equilibrium liquid to equilibrium vapor (liquid gain) – i.e., the approach of Giggenbach (1980), but assigning the pivotal role to steam rather than liquid water –, saturated vapors, saturated vapors affected by removal of equilibrium liquid (steam condensate), and superheated (dry) vapors. The application of the H2O–CO2–H2S–H2–CH4–CO–COS geothermometer enabled us to refine the outcomes obtained by using the graphical tools and functions based on gas equilibria for the H2O–CO2–H2–CH4–CO system. The improved geothermometric results were achieved by accounting for the effects of the reaction COS + H2 = CO +H2S, which likely governs the final re-equilibration of CO and COS due to their low concentrations and the high thermodynamic probability of spontaneous progress under geothermal conditions. Nevertheless, it cannot be ruled out that the concentration of COS in some fluid samples of this study may also be influenced by the reaction COS + H2O = CO2 + H2S. This work demonstrates the analytical and interpretative value of incorporating COS in routine determinations of geothermal gases and underscores the need for further experimental and theoretical studies to better constrain the kinetics and mechanisms of the reaction converting COS and H2 in CO and H2S.
虽然羰基硫化物（COS）长期以来一直被认为是一种潜在的有价值的地热指标，但由于分析数据的缺乏，其使用受到限制，主要是由于20世纪90年代仪器的限制。本文为H2O-CO2-H2S-H2-CH4-CO-COS系统开发了新的地热测量函数和图形工具，并将其应用于意大利Larderello和冰岛Krafla地热流体的新数据。重新评价了COS和其他气体的热力学数据，外推了气液分布系数，并建立了不同含水层条件下的气体平衡方程。饱和纯液态水，通过向平衡蒸汽中加入平衡液体而产生的两相液体加蒸汽混合物（液体增益）-即Giggenbach（1980）的方法，但将关键作用赋予蒸汽而不是液态水-饱和蒸汽，通过去除平衡液体（蒸汽冷凝物）影响的饱和蒸汽，以及过热（干燥）蒸汽。H2O-CO2-H2S-H2-CH4-CO-COS地温计的应用使我们能够利用基于H2O-CO2-H2-CH4-CO体系气体平衡的图形工具和函数来改进所得结果。考虑到COS +H2 = CO +H2S反应的影响，该反应可能控制了CO和COS的最终再平衡，因为它们的低浓度和在地热条件下自发进展的高热力学概率。但也不能排除本研究中部分流体样品中COS的浓度也可能受到COS + H2O = CO2 + H2S反应的影响。这项工作证明了COS在地热气体常规测定中的分析和解释价值，并强调了进一步的实验和理论研究的必要性，以更好地约束CO和H2S中COS和H2转化反应的动力学和机制。
{"title":"Hydrothermal gas equilibria in the H2O–CO2–H2S–H2–CH4–CO–COS system","authors":"M. Lelli , E. Dallara , L. Marini , G. Bini","doi":"10.1016/j.geothermics.2026.103606","DOIUrl":"10.1016/j.geothermics.2026.103606","url":null,"abstract":"<div><div>Although carbonyl sulfide (COS) has long been recognized as a potentially valuable geothermometric indicator, its use has been limited by the scarcity of analytical data, mainly due to instrumental limitations in the 1990s. In this work, new geothermometric functions and graphical tools were developed for the H<sub>2</sub>O–CO<sub>2</sub>–H<sub>2</sub>S–H<sub>2</sub>–CH<sub>4</sub>–CO–COS system and applied to new data of Larderello (Italy) and Krafla (Iceland) geothermal fluids. Thermodynamic data of COS and other gas species were re-evaluated, vapor–liquid distribution coefficients were extrapolated, and the gas equilibria were formulated for different aquifer conditions: saturated pure liquid water, two-phase liquid plus vapor mixtures produced by addition of equilibrium liquid to equilibrium vapor (liquid gain) – i.e., the approach of Giggenbach (1980), but assigning the pivotal role to steam rather than liquid water –, saturated vapors, saturated vapors affected by removal of equilibrium liquid (steam condensate), and superheated (dry) vapors. The application of the H<sub>2</sub>O–CO<sub>2</sub>–H<sub>2</sub>S–H<sub>2</sub>–CH<sub>4</sub>–CO–COS geothermometer enabled us to refine the outcomes obtained by using the graphical tools and functions based on gas equilibria for the H<sub>2</sub>O–CO<sub>2</sub>–H<sub>2</sub>–CH<sub>4</sub>–CO system. The improved geothermometric results were achieved by accounting for the effects of the reaction COS + H<sub>2</sub> = CO +H<sub>2</sub>S, which likely governs the final re-equilibration of CO and COS due to their low concentrations and the high thermodynamic probability of spontaneous progress under geothermal conditions. Nevertheless, it cannot be ruled out that the concentration of COS in some fluid samples of this study may also be influenced by the reaction COS + H<sub>2</sub>O = CO<sub>2</sub> + H<sub>2</sub>S. This work demonstrates the analytical and interpretative value of incorporating COS in routine determinations of geothermal gases and underscores the need for further experimental and theoretical studies to better constrain the kinetics and mechanisms of the reaction converting COS and H<sub>2</sub> in CO and H<sub>2</sub>S.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103606"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022514","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 : 2026-03-01Epub Date: 2026-01-23DOI: 10.1016/j.geothermics.2026.103613
Binghong Fan , Ximin Bai , Hailong Ye , Gongxin Chen , Yanyan Li , Ziqi Zeng , Wei Chen
Ningdu County is an important geothermal rich area in Jiangxi Province, with superior resource endowment. Previous studies have mostly focused on single geothermal fields with high exploration degree and temperature. There is a lack of systematicness in the research on the regional and overall spatial distribution characteristics, evolution laws and deep genesis mechanisms of geothermal water chemistry. This paper focuses on the Ningdu Zhantian-Huitong geothermal area, collecting and analyzing 23 groups of geothermal water samples, 1 group of surface water samples, 2 groups of cold spring water samples, and 11 groups of δD and δ18O isotope data. By comprehensively applying methods such as water chemistry analysis, stable isotopes, and geothermal temperature estimation, The chemical characteristics and component evolution of geothermal water, isotopic characteristics, estimation of heat storage temperature, sources and genesis mechanisms of geothermal water were systematically studied. The results show that the geothermal resources in the area are controlled by the northeast fault structure. The water chemical types are HCO3·SO4-Na and SO4·HCO3-Na types, and the recharge source is atmospheric precipitation at an elevation of 379-521m. The proportion of cold water mixed in is as high as 70% to 89%. It is estimated that the shallow heat storage temperature is 89 to 152°C, the deep heat storage temperature is 219 to 250°C, and the circulation depth is 2377 to 7743 meters. The genesis mechanism of geothermal water, which is "fracture channel conduction - dual heat source heating - water-rock reaction - cold and hot water mixing", has been revealed. The research results can provide a scientific basis for the heating and storage expansion of geothermal fields in the area and the exploration and development of concealed geothermal resources.
{"title":"Analysis of hydrochemical characteristics and geothermal genesis mechanism of the Zhantian-Huitong geothermal belt, Ningdu County","authors":"Binghong Fan , Ximin Bai , Hailong Ye , Gongxin Chen , Yanyan Li , Ziqi Zeng , Wei Chen","doi":"10.1016/j.geothermics.2026.103613","DOIUrl":"10.1016/j.geothermics.2026.103613","url":null,"abstract":"<div><div>Ningdu County is an important geothermal rich area in Jiangxi Province, with superior resource endowment. Previous studies have mostly focused on single geothermal fields with high exploration degree and temperature. There is a lack of systematicness in the research on the regional and overall spatial distribution characteristics, evolution laws and deep genesis mechanisms of geothermal water chemistry. This paper focuses on the Ningdu Zhantian-Huitong geothermal area, collecting and analyzing 23 groups of geothermal water samples, 1 group of surface water samples, 2 groups of cold spring water samples, and 11 groups of δD and δ<sup>18</sup>O isotope data. By comprehensively applying methods such as water chemistry analysis, stable isotopes, and geothermal temperature estimation, The chemical characteristics and component evolution of geothermal water, isotopic characteristics, estimation of heat storage temperature, sources and genesis mechanisms of geothermal water were systematically studied. The results show that the geothermal resources in the area are controlled by the northeast fault structure. The water chemical types are HCO<sub>3</sub>·SO<sub>4</sub>-Na and SO<sub>4</sub>·HCO<sub>3</sub>-Na types, and the recharge source is atmospheric precipitation at an elevation of 379-521m. The proportion of cold water mixed in is as high as 70% to 89%. It is estimated that the shallow heat storage temperature is 89 to 152°C, the deep heat storage temperature is 219 to 250°C, and the circulation depth is 2377 to 7743 meters. The genesis mechanism of geothermal water, which is \"fracture channel conduction - dual heat source heating - water-rock reaction - cold and hot water mixing\", has been revealed. The research results can provide a scientific basis for the heating and storage expansion of geothermal fields in the area and the exploration and development of concealed geothermal resources.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103613"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022516","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 : 2026-03-01Epub Date: 2025-12-26DOI: 10.1016/j.geothermics.2025.103580
Lingkan Finna Christi , Mrityunjay Singh , Ingo Sass , Ben Norden , Günter Zimmermann , Maximilian Frick , Monika Hölzel , Hannes Hofmann
This study demonstrates the potential of Deep Borehole Heat Exchangers (DBHEs) technology to unlock low-risk, cost-effective geothermal energy in Groß Schönebeck by repurposing existing wells. The well doublet features approximately 1.5 km of the Zechstein formation, a thermally conductive and impermeable formation ideal for DBHE applications. A numerical simulation using CMG STARS was used to optimize the installation of a DBHE to a depth of 3800 m MD. At this completion depth, both wells achieved thermal power ranging from 500–750 kilowatts (kW) and outlet temperatures in the range of 49–67 °C with the flow rates ranging from 10 to 25 m3 h−1 and inlet temperatures between 10–25 °C. With the model, we explored the relationship between tubing dimensions and materials, as well as the impact of varying operational parameters on the performance of the DBHEs. Our analysis confirms direct heating is the most suitable application, with a Levelized Cost of Heat (LCOH) of 7-14 ct €/kWh within the given operational parameters. While electricity generation is not feasible, the study highlights a cost-effective, low-risk geothermal heating solution by repurposing existing wells as DBHEs. Key requirements include deployment of minimum 2.88”/2.44” (OD/ID) vacuum-insulated tubing (or equivalent) with low thermal conductivity ( 0.06 W m−1 K−1), and subsequent field validation of heat transfer parameters. This approach minimizes investment and risk by utilizing existing infrastructure, but requires close proximity between the heat source and the consumer. Future research and feasibility studies should prioritize well integrity and seamless integration with surface infrastructure and district heating networks.
该研究展示了深孔热交换器（DBHEs）技术的潜力，通过重新利用现有井，在Groß Schönebeck开发低风险、低成本的地热能。该双井的特点是约1.5公里的Zechstein地层，这是一种导热、不渗透的地层，非常适合DBHE应用。使用CMG STARS进行数值模拟，优化DBHE的安装深度为3800 m MD。在该完井深度，两口井的热功率为500-750千瓦，出口温度为49-67℃，流量为10 - 25 m3 h - 1，进口温度为10 - 25℃。通过该模型，我们探索了油管尺寸与材料之间的关系，以及不同操作参数对dbh性能的影响。我们的分析证实，直接加热是最合适的应用，在给定的运行参数下，平均热成本（LCOH）为7-14 ct€/kWh。虽然发电是不可行的，但该研究强调了一种经济、低风险的地热加热解决方案，即将现有井重新利用为dbh。关键要求包括部署至少2.88 " /2.44 "（外径/内径）真空绝缘管（或同等材料），具有低导热系数（≤0.06 W m−1 K−1），以及随后的传热参数现场验证。这种方法通过利用现有的基础设施将投资和风险降到最低，但需要热源和消费者之间的距离很近。未来的研究和可行性研究应优先考虑井的完整性和与地面基础设施和区域供热网络的无缝集成。
{"title":"Design optimization of Deep Borehole Heat Exchangers (DBHEs) for well retrofitting","authors":"Lingkan Finna Christi , Mrityunjay Singh , Ingo Sass , Ben Norden , Günter Zimmermann , Maximilian Frick , Monika Hölzel , Hannes Hofmann","doi":"10.1016/j.geothermics.2025.103580","DOIUrl":"10.1016/j.geothermics.2025.103580","url":null,"abstract":"<div><div>This study demonstrates the potential of Deep Borehole Heat Exchangers (DBHEs) technology to unlock low-risk, cost-effective geothermal energy in Groß Schönebeck by repurposing existing wells. The well doublet features approximately 1.5 km of the Zechstein formation, a thermally conductive and impermeable formation ideal for DBHE applications. A numerical simulation using CMG STARS was used to optimize the installation of a DBHE to a depth of 3800 m MD. At this completion depth, both wells achieved thermal power ranging from 500–750 kilowatts (kW) and outlet temperatures in the range of 49–67 °C with the flow rates ranging from 10 to 25 m<sup>3</sup> <!-->h<sup>−1</sup> and inlet temperatures between 10–25 °C. With the model, we explored the relationship between tubing dimensions and materials, as well as the impact of varying operational parameters on the performance of the DBHEs. Our analysis confirms direct heating is the most suitable application, with a Levelized Cost of Heat (LCOH) of 7-14 ct €/kWh within the given operational parameters. While electricity generation is not feasible, the study highlights a cost-effective, low-risk geothermal heating solution by repurposing existing wells as DBHEs. Key requirements include deployment of minimum 2.88”/2.44” (OD/ID) vacuum-insulated tubing (or equivalent) with low thermal conductivity (<span><math><mo>≤</mo></math></span> 0.06<!--> <!-->W<!--> <!-->m<sup>−1</sup> <!-->K<sup>−1</sup>), and subsequent field validation of heat transfer parameters. This approach minimizes investment and risk by utilizing existing infrastructure, but requires close proximity between the heat source and the consumer. Future research and feasibility studies should prioritize well integrity and seamless integration with surface infrastructure and district heating networks.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103580"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145839918","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 : 2026-03-01Epub Date: 2025-12-20DOI: 10.1016/j.geothermics.2025.103586
Dejian Zhou , Quan Liu , Huhao Gao , Alexandru Tatomir , Martin Sauter
Thermo-sensitive (TS) tracers offer significant potential for enhancing the understanding of heat transfer in porous media and ascertaining financial revenues by reducing reservoir lifetime prediction uncertainty. Based on the demonstrated feasibility of TS tracers for estimating the thermal front positions in homogeneous systems, the study expands the application of TS tracers to heterogeneous conditions. Assuming that heat and tracers follow the same preferential flow pathways, we derived an analytical solution to estimate the thermal breakthrough time in the reservoir with highly heterogeneous permeability. The analytical estimates are validated against the simulation results. The findings show a strong agreement on thermal breakthrough time, with a correlation coefficient exceeding 0.99, between the analytical estimates and simulation results. Additionally, the estimation accuracy remains robust across a wider range of injection and reservoir conditions, including the variation of injection rate, temperature, and reservoir porosity. However, the reliability of this approach critically relies on the ability to accurately interpret the tracer concentration breakthrough curve. The TS tracer technology demonstrates high feasibility only when the breakthrough curve can be effectively deconvoluted into contributions from individual preferential flow pathways.
{"title":"An inversion method to estimate thermal breakthrough time using thermo-sensitive tracer in reservoirs with highly heterogeneous permeability","authors":"Dejian Zhou , Quan Liu , Huhao Gao , Alexandru Tatomir , Martin Sauter","doi":"10.1016/j.geothermics.2025.103586","DOIUrl":"10.1016/j.geothermics.2025.103586","url":null,"abstract":"<div><div>Thermo-sensitive (TS) tracers offer significant potential for enhancing the understanding of heat transfer in porous media and ascertaining financial revenues by reducing reservoir lifetime prediction uncertainty. Based on the demonstrated feasibility of TS tracers for estimating the thermal front positions in homogeneous systems, the study expands the application of TS tracers to heterogeneous conditions. Assuming that heat and tracers follow the same preferential flow pathways, we derived an analytical solution to estimate the thermal breakthrough time in the reservoir with highly heterogeneous permeability. The analytical estimates are validated against the simulation results. The findings show a strong agreement on thermal breakthrough time, with a correlation coefficient exceeding 0.99, between the analytical estimates and simulation results. Additionally, the estimation accuracy remains robust across a wider range of injection and reservoir conditions, including the variation of injection rate, temperature, and reservoir porosity. However, the reliability of this approach critically relies on the ability to accurately interpret the tracer concentration breakthrough curve. The TS tracer technology demonstrates high feasibility only when the breakthrough curve can be effectively deconvoluted into contributions from individual preferential flow pathways.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103586"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840042","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 : 2026-03-01Epub Date: 2026-01-31DOI: 10.1016/j.geothermics.2026.103614
Wenjie Sun , Jiabin Duan , Mingliang Liu , Fangyang Hu , Xiaodong Jiang , Yanlong Kong
Geothermal waters in certain regions of Tibet, particularly those characterized by intense tectonic activity, are exceptionally enriched in lithium (Li), rubidium (Rb), and cesium (Cs). However, the primary sources of these elements within Tibetan geothermal systems remain debated. Clarifying whether these elements are derived predominantly from water-rock interaction or magmatic fluid input is essential for a comprehensive understanding of the region’s geothermal systems. Previous studies lacked quantitative analysis methods using water-rock interaction simulation experiments. To address this gap, we conducted laboratory simulations using 10-million-years-old biotite granite from the Yangbajing area, performing high-temperature and high-pressure experiments at 200 °C and 20 MPa over 62 days. The results yield a Li:Rb:Cs ratio of approximately 48:64:1, which starkly contrast with the ratio observed in natural geothermal waters (around 5.7:1:2.1). This significant discrepancy suggests that there must be an additional geochemical process that strongly modifies the Li, Rb, and Cs ratios in natural geothermal waters. Moreover, in the Yangbajing-Gulu rift, the concentrations of Li, Rb, and Cs show a strong correlation with Cl, a tracer indicative of magmatic fluid input, while the correlations between δ¹⁸O and the concentrations of Li, Rb, and Cs are weaker. The geothermal waters exhibit a Cs > Rb pattern, similar to other geothermal systems with magmatic fluid input. Combined with geophysical evidence of shallow melt bodies beneath the rift, these findings indicate that magmatic fluid input is a key factor controlling the enrichment of Li, Rb, and Cs in the geothermal waters of the Yangbajing-Gulu rift. This study highlights the magmatic source mechanism for rare metal supply in Tibetan geothermal waters and provides critical insights into the metallogenic models of Tibetan geothermal systems.
{"title":"Experimental and geochemical evidence for magmatic origin of Li-Rb-Cs in geothermal waters of the Yangbajing-Gulu Rift, Tibet","authors":"Wenjie Sun , Jiabin Duan , Mingliang Liu , Fangyang Hu , Xiaodong Jiang , Yanlong Kong","doi":"10.1016/j.geothermics.2026.103614","DOIUrl":"10.1016/j.geothermics.2026.103614","url":null,"abstract":"<div><div>Geothermal waters in certain regions of Tibet, particularly those characterized by intense tectonic activity, are exceptionally enriched in lithium (Li), rubidium (Rb), and cesium (Cs). However, the primary sources of these elements within Tibetan geothermal systems remain debated. Clarifying whether these elements are derived predominantly from water-rock interaction or magmatic fluid input is essential for a comprehensive understanding of the region’s geothermal systems. Previous studies lacked quantitative analysis methods using water-rock interaction simulation experiments. To address this gap, we conducted laboratory simulations using 10-million-years-old biotite granite from the Yangbajing area, performing high-temperature and high-pressure experiments at 200 °C and 20 MPa over 62 days. The results yield a Li:Rb:Cs ratio of approximately 48:64:1, which starkly contrast with the ratio observed in natural geothermal waters (around 5.7:1:2.1). This significant discrepancy suggests that there must be an additional geochemical process that strongly modifies the Li, Rb, and Cs ratios in natural geothermal waters. Moreover, in the Yangbajing-Gulu rift, the concentrations of Li, Rb, and Cs show a strong correlation with Cl, a tracer indicative of magmatic fluid input, while the correlations between δ¹⁸O and the concentrations of Li, Rb, and Cs are weaker. The geothermal waters exhibit a Cs > Rb pattern, similar to other geothermal systems with magmatic fluid input. Combined with geophysical evidence of shallow melt bodies beneath the rift, these findings indicate that magmatic fluid input is a key factor controlling the enrichment of Li, Rb, and Cs in the geothermal waters of the Yangbajing-Gulu rift. This study highlights the magmatic source mechanism for rare metal supply in Tibetan geothermal waters and provides critical insights into the metallogenic models of Tibetan geothermal systems.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103614"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077950","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 : 2026-03-01Epub Date: 2025-12-15DOI: 10.1016/j.geothermics.2025.103569
Mangu Hu , Tianyu Fu , Xiaobin Yang , Lei Peng , Chun Wang , Xiangfeng Lv
Accurate identification and quantitative characterization of fractures in hot dry rock (HDR) reservoirs are of great significance for the efficient development of geothermal resources. To address the challenges associated with precise fracture recognition and quantification, an improved fracture identification model named TSD-Unet is proposed in this study. This model is constructed by integrating the Spatial Group-wise Enhance (SGE) module and Dynamic Snake Convolution (DSC) module into the U-Net architecture. This integration enables the TSD-Unet model to extract both spatial and multi-morphological features of fractures from granite failure images. The SGE and DSC modules, inserted after the convolutional layers, allow the model to effectively combine spatial and morphological features of fractures. Ablation experiments and multi-model comparison experiments were conducted using a granite fracture image dataset. The comparison results demonstrate the competitiveness of the TSD-Unet model in segmentation performance, achieving an accuracy (Acc) of 62.88 % and an intersection over union (IoU) of 46.06 %. Compared to the traditional U-Net model, TSD-Unet shows improvements of 8.02 % in Acc and 9.51 % in IoU. Based on the segmentation results and the proposed feature computation method, quantitative analyses were performed on fracture characteristics such as length, area, average width, and maximum width, revealing that the results based on TSD-Unet closely match actual conditions. This research provides a precise and efficient method for intelligent fracture identification and feature extraction in HDR reservoirs, offering significant theoretical guidance for improving the efficiency of geothermal resource exploitation.
{"title":"Fracture identification in hot dry rock using TSD-Unet: From feature extraction to quantitative analysis of geometric parameters","authors":"Mangu Hu , Tianyu Fu , Xiaobin Yang , Lei Peng , Chun Wang , Xiangfeng Lv","doi":"10.1016/j.geothermics.2025.103569","DOIUrl":"10.1016/j.geothermics.2025.103569","url":null,"abstract":"<div><div>Accurate identification and quantitative characterization of fractures in hot dry rock (HDR) reservoirs are of great significance for the efficient development of geothermal resources. To address the challenges associated with precise fracture recognition and quantification, an improved fracture identification model named TSD-Unet is proposed in this study. This model is constructed by integrating the Spatial Group-wise Enhance (SGE) module and Dynamic Snake Convolution (DSC) module into the U-Net architecture. This integration enables the TSD-Unet model to extract both spatial and multi-morphological features of fractures from granite failure images. The SGE and DSC modules, inserted after the convolutional layers, allow the model to effectively combine spatial and morphological features of fractures. Ablation experiments and multi-model comparison experiments were conducted using a granite fracture image dataset. The comparison results demonstrate the competitiveness of the TSD-Unet model in segmentation performance, achieving an accuracy (Acc) of 62.88 % and an intersection over union (IoU) of 46.06 %. Compared to the traditional U-Net model, TSD-Unet shows improvements of 8.02 % in Acc and 9.51 % in IoU. Based on the segmentation results and the proposed feature computation method, quantitative analyses were performed on fracture characteristics such as length, area, average width, and maximum width, revealing that the results based on TSD-Unet closely match actual conditions. This research provides a precise and efficient method for intelligent fracture identification and feature extraction in HDR reservoirs, offering significant theoretical guidance for improving the efficiency of geothermal resource exploitation.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103569"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790720","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 : 2026-03-01Epub Date: 2025-12-16DOI: 10.1016/j.geothermics.2025.103572
João Luiz Botega Nogari, Cristina de Hollanda Cavalcanti Tsuha
The soil thermal conductivity governs the heat transfer process within the soil and is a key parameter in various engineering applications, including shallow geothermal energy exploitation, thermal energy storage, underground power cable systems, nuclear waste isolation, among others. This parameter can be determined through various methods, including predictive models based on soil characteristics, laboratory tests on small soil samples, in-situ needle probe, field thermal response tests (TRT) on larger soil volumes, and the field thermal cone dissipation test (T-CPT), which utilize the well-known cone penetration test (CPT) device. In-situ tests offer the advantage of providing rapid results for soil thermal conductivity under actual field conditions. This study focuses on field measurements of the thermal conductivity of soils based on the thermal cone dissipation test, using a low-cost and portable equipment compared to the conventional CPT apparatus. For this purpose, the cone tip of a Dynamic Probing Light (DPL) was modified to estimate soil thermal conductivity and named T-DPL (Thermal Dynamic Probing Light). The T-DPL equipment is easy to operate, lightweight, and manually controlled. The validation of the test procedure was demonstrated through model tank tests in both dry and saturated sand. Following laboratory validation, T-DPL tests were conducted at an unsaturated soil site in Brazil. The moisture content and groundwater table at the test site vary seasonally, influencing the previously measured ground thermal conductivity results from TRT experiments. The use of the T-DPL provided consistent results and effectively detected the impact of seasonal moisture content variations on soil thermal conductivity.
{"title":"Evaluation of the use of a thermal dynamic probing light (T-DPL) for the field determination of soil thermal conductivity","authors":"João Luiz Botega Nogari, Cristina de Hollanda Cavalcanti Tsuha","doi":"10.1016/j.geothermics.2025.103572","DOIUrl":"10.1016/j.geothermics.2025.103572","url":null,"abstract":"<div><div>The soil thermal conductivity governs the heat transfer process within the soil and is a key parameter in various engineering applications, including shallow geothermal energy exploitation, thermal energy storage, underground power cable systems, nuclear waste isolation, among others. This parameter can be determined through various methods, including predictive models based on soil characteristics, laboratory tests on small soil samples, in-situ needle probe, field thermal response tests (TRT) on larger soil volumes, and the field thermal cone dissipation test (T-CPT), which utilize the well-known cone penetration test (CPT) device. In-situ tests offer the advantage of providing rapid results for soil thermal conductivity under actual field conditions. This study focuses on field measurements of the thermal conductivity of soils based on the thermal cone dissipation test, using a low-cost and portable equipment compared to the conventional CPT apparatus. For this purpose, the cone tip of a Dynamic Probing Light (DPL) was modified to estimate soil thermal conductivity and named T-DPL (Thermal Dynamic Probing Light). The T-DPL equipment is easy to operate, lightweight, and manually controlled. The validation of the test procedure was demonstrated through model tank tests in both dry and saturated sand. Following laboratory validation, T-DPL tests were conducted at an unsaturated soil site in Brazil. The moisture content and groundwater table at the test site vary seasonally, influencing the previously measured ground thermal conductivity results from TRT experiments. The use of the T-DPL provided consistent results and effectively detected the impact of seasonal moisture content variations on soil thermal conductivity.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103572"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790747","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 : 2026-03-01Epub Date: 2025-12-17DOI: 10.1016/j.geothermics.2025.103574
Nicholas Fry, Roman Shor, Aggrey Mwesigye
This study extends a previously established System Dynamics (SD) geothermal energy network (GEN) modeling framework to evaluate how regional thermal demand, auxiliary equipment strategies, and operational conditions influence GEN performance across varied climatic settings, therefore influencing market viability. Using thermal load profiles from ResStock and ComStock for multifamily and medium office buildings in Washington, Illinois, and New York, the study simulates GEN behavior with configurations including single-source borehole heat exchangers, passive cooling, dry cooler hybridization, and waste heat injection to the ground heat exchangers. The SD model captures nonlinear feedback between seasonal demand patterns, auxiliary system activation, and formation thermal conductivities, enabling scenario-based sensitivity analyses with grid searches using control regimes. Results indicate that both climatic conditions and operational controls have measurable impacts on system performance, system longevity, auxiliary equipment cycling, and electricity consumption. The findings suggest that tailored GEN configurations, responsive to regional thermal conditions, can mitigate oversizing, reduce parasitic loads, and enhance techno-economic outcomes. These tailored solutions are, however, not complicated to envision and the study findings suggest there is little need for perfecting borehole heat exchanger sizing. Wide scale adoption can occur now using simple operational strategies to stabilize year-over-year costs. Limitations in site-specific data are apparent, but the regional insights provided offer valuable guidance for engineers, geoscientists, and policymakers engaged in GEN deployment. This work underscores the importance of feedback-oriented modeling to anticipate the thermal behaviors of GENs and to inform infrastructure investment decisions in the context of decarbonization mandates.
{"title":"Demand, operational conditions, and impacts on geothermal energy networks","authors":"Nicholas Fry, Roman Shor, Aggrey Mwesigye","doi":"10.1016/j.geothermics.2025.103574","DOIUrl":"10.1016/j.geothermics.2025.103574","url":null,"abstract":"<div><div>This study extends a previously established System Dynamics (SD) geothermal energy network (GEN) modeling framework to evaluate how regional thermal demand, auxiliary equipment strategies, and operational conditions influence GEN performance across varied climatic settings, therefore influencing market viability. Using thermal load profiles from ResStock and ComStock for multifamily and medium office buildings in Washington, Illinois, and New York, the study simulates GEN behavior with configurations including single-source borehole heat exchangers, passive cooling, dry cooler hybridization, and waste heat injection to the ground heat exchangers. The SD model captures nonlinear feedback between seasonal demand patterns, auxiliary system activation, and formation thermal conductivities, enabling scenario-based sensitivity analyses with grid searches using control regimes. Results indicate that both climatic conditions and operational controls have measurable impacts on system performance, system longevity, auxiliary equipment cycling, and electricity consumption. The findings suggest that tailored GEN configurations, responsive to regional thermal conditions, can mitigate oversizing, reduce parasitic loads, and enhance techno-economic outcomes. These tailored solutions are, however, not complicated to envision and the study findings suggest there is little need for perfecting borehole heat exchanger sizing. Wide scale adoption can occur now using simple operational strategies to stabilize year-over-year costs. Limitations in site-specific data are apparent, but the regional insights provided offer valuable guidance for engineers, geoscientists, and policymakers engaged in GEN deployment. This work underscores the importance of feedback-oriented modeling to anticipate the thermal behaviors of GENs and to inform infrastructure investment decisions in the context of decarbonization mandates.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103574"},"PeriodicalIF":3.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790748","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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