Geothermics最新文献

{"title":"Hydrothermal gas equilibria in the H2O–CO2–H2S–H2–CH4–CO–COS system","authors":"M. Lelli ,&nbsp;E. Dallara ,&nbsp;L. Marini ,&nbsp;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 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.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103606"},"PeriodicalIF":3.9,"publicationDate":"2026-01-22","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}

{"title":"Three-dimensional lithospheric-scale thermal model as supporting tool for new exploration campaigns for geothermal resources: Insights from the Calabria region (Southern Italy)","authors":"G. Vespasiano ,&nbsp;G. Floridia ,&nbsp;M. Giuffrida ,&nbsp;M. Viccaro ,&nbsp;A. Bloise ,&nbsp;R. De Rosa ,&nbsp;M. Cacace ,&nbsp;I. Fuoco ,&nbsp;M.F. La Russa ,&nbsp;F. Muto ,&nbsp;R. Dominici ,&nbsp;L. Russo ,&nbsp;M. Cipriani ,&nbsp;A. Guido ,&nbsp;G. Maruca ,&nbsp;C. Apollaro","doi":"10.1016/j.geothermics.2026.103604","DOIUrl":"10.1016/j.geothermics.2026.103604","url":null,"abstract":"<div><div>This study presents the first lithosphere-scale, steady-state 3D thermal model of the Calabria region (Southern Italy), developed to support the geothermal resource assessment and exploration. By integrating geological, geophysical, and thermal datasets, a high-resolution 3D geological model was built and used as a structural framework for finite-element thermal simulations. The simulations incorporated spatially variable thermal conductivity, radiogenic heat production, and a range of basal heat flux values applied at the crust-mantle (Moho) interface. Five thermal scenarios were tested and calibrated against 254 measured temperature data points from exploration wells. The results reveal pronounced lateral thermal heterogeneity, with temperatures exceeding 90 °C at 3 km depth beneath the Ionian basins, driven by the local crustal structure, sedimentary blanketing, and Moho geometry. While the model delineates zones suitable for low-to-medium enthalpy geothermal exploitation (1-3 km), deeper high-enthalpy targets remain less constrained and deserve further investigation. This study establishes a geologically consistent framework that enhances the understanding of the regional thermal regime and serves as a strategic tool for guiding future geothermal exploration in Calabria.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103604"},"PeriodicalIF":3.9,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022973","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}

{"title":"Improving borehole fracture characterization using oriented sidewall cores for geothermal assessment – an example in central New York State USA","authors":"Sean A. Fulcher ,&nbsp;Teresa E. Jordan ,&nbsp;Stephen E. Laubach ,&nbsp;Sara J. Elliott ,&nbsp;Valeria Nogales Herrera","doi":"10.1016/j.geothermics.2025.103589","DOIUrl":"10.1016/j.geothermics.2025.103589","url":null,"abstract":"<div><div>In New York State and Pennsylvania, USA, Precambrian metamorphic and intrusive rocks and Cambrian to Lower Ordovician sedimentary rocks are reservoir targets for deep direct-use geothermal development. Evaluation of natural fractures and structures in the potential reservoir units at the Cornell University Borehole Observatory site was conducted through cross-scale evaluation of oriented sidewall cores, borehole image (BHI), and far-field acoustic survey data. Oriented sidewall cores in the basement complex (Cayuta Formation) reveal metasediments containing foliations, lineations, mineral-filled fractures, and breccia intervals. Basement sidewall core fracture data aid identification of fractures in BHI surveys riddled with borehole breakouts. In contrast, sidewall and image log data for the Cambrian-Ordovician sedimentary section show that open fractures are present and allow orientation and abundance to be estimated. At various depths sandstone and dolostone sidewall cores contain quartz-filled or carbonate-filled bed-normal and -parallel microfractures. Four subvertical microfracture sets, formed sequentially, strike NW-SE (F1), NE-SW (F2), N-S (F3), and WSW-ENE (F4). Microfracture set orientations F1, F2, and F4 match interpretations of acoustic fracture anomalies (open fractures) located tens of meters from the wellbore. In the uppermost Galway Formation sandstone, common microfracture apertures are 0.001 to 0.01 mm. The widest microfractures transition to quartz-lined and bridged open macrofractures. An open vertical macrofracture in Galway sandstone is observed in BHI surveys and a sidewall core, effectively ground-truthing the F4 fracture set. Based on comparison of core fractures with borehole image survey features, differentiation of natural from drilling-induced fractures reveals three sedimentary rock zones of elevated natural fracture frequency.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103589"},"PeriodicalIF":3.9,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022513","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}

{"title":"Thermal conductivity and heat flow modeling of petroleum exploration and research wells onshore Svalbard","authors":"Matthijs Nuus ,&nbsp;Sven Fuchs ,&nbsp;Aleksandra Smyrak-Sikora ,&nbsp;Tabea Kubutat ,&nbsp;Kim Senger","doi":"10.1016/j.geothermics.2025.103585","DOIUrl":"10.1016/j.geothermics.2025.103585","url":null,"abstract":"<div><div>Thermal properties such as thermal conductivity and radiogenic heat production are crucial to provide reliable heat flow estimates, with direct implications on geothermal exploration. Such parameters can be derived from laboratory analyses on drill core samples or estimated from standard wireline logs. Onshore the Arctic archipelago of Svalbard, geothermal energy is being considered as an alternative to the diesel-fueled present-day energy supply. However, reliable thermal conductivity estimates are only available from fully cored research boreholes covering the Late Triassic to Paleogene sedimentary succession. Adequate temperatures for geothermal district heating (80 °C) are only reached at ca. 2 km depth beneath Longyearbyen, Svalbard’s largest settlement. At such depths, the thermal properties of the subsurface are unconstrained. In this contribution, we use petroleum exploration boreholes drilled to depths of up to 3.3 km onshore Svalbard to derive thermal properties from wireline logs for the Carboniferous to Paleogene succession. Lithology logs of ten boreholes were digitized and used as the foundation for thermal modeling. Based on these logs, we implemented two modeling cases: (1) assigning generalized thermal properties by lithology type, and (2) using thermal properties calculated directly from wireline logs, which also require lithological information. Our calculations suggest variable thermal conductivity from 0.4 to 4.2 W/mK, largely controlled by lithology. In the uppermost 1 km, where fully cored research boreholes are available, we compared the calculated thermal properties with the measured data from these boreholes. We observed similar trends between lithology and the calculated thermal conductivity; however, the calculated values are generally slightly lower than the values measured in the laboratory. Subsequently, we use the regional thermal properties as input to 1D heat flow modeling of ten boreholes and a hypothetical deep geothermal borehole beneath Longyearbyen. The calculated heat flow values span from 60 to 147 <span><math><msup><mrow><mtext>mW/m</mtext></mrow><mrow><mn>2</mn></mrow></msup></math></span>, with the highest values obtained from the Raddedalen borehole in Edgeøya. By calculating thermal properties from wireline logs, we allow for more accurate heat flow models, providing valuable insights into the spatial distribution of heat flow across Svalbard and its thermal state.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103585"},"PeriodicalIF":3.9,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022512","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}

{"title":"Early-phase geothermal prospecting using remote sensing and machine learning: application to Buharkent and Germencik fields, Türkiye","authors":"Hakan Oktay Aydınlı,&nbsp;Gordana Kaplan,&nbsp;Saye Nihan Çabuk","doi":"10.1016/j.geothermics.2026.103603","DOIUrl":"10.1016/j.geothermics.2026.103603","url":null,"abstract":"<div><div>The extensive use of fossil fuels worldwide is one of the major reason of the global climate crisis. Renewable energy is the most promising source used all over the world to reduce the reliance on fossil fuels. Geothermal energy is considered a trustworthy alternative energy source to replace fossil fuels due to its versatility and sustainability. Despite the geothermal energy’s major advantages, the usage of geothermal energy is still limited due to the high costs of conventional exploration techniques and the low accuracy results of these techniques, specifically in the wildcat areas. To address these challenges in exploration phases, satellite-based remote sensing data can be used to lower the early-phase exploration costs. This study aims to develop an early-phase geothermal exploration model that utilises remote sensing data through a machine learning approach. Lineament Density (LD), Hydrothermal Alterations (HA), and Land Surface Temperature (LST) were the most common geothermal surface manifestations used in the model as inputs. These inputs were integrated with K-means and Random Forest (RF) algorithms owing to their capability of handling large and complex datasets. In this study, Buharkent and Germencik geothermal fields from Türkiye were selected as study areas due to their substantial reserves and long-term production, and mature field characteristics. The results of the analysis revealed that the model accuracy was 79% and 59% in Buharkent and Germencik fields, respectively. The study’s findings demonstrate that satellite-based remote sensing data, when combined with machine learning techniques, can be considered a supportive tool for geothermal exploration alongside conventional methods.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103603"},"PeriodicalIF":3.9,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976969","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}

{"title":"Mechanical behavior and constitutive model of thermally damaged granite: Insights from experiments","authors":"Ming Min ,&nbsp;Qiang Zhang ,&nbsp;Xiao-Suo Wu ,&nbsp;Bin-Song Jiang","doi":"10.1016/j.geothermics.2026.103602","DOIUrl":"10.1016/j.geothermics.2026.103602","url":null,"abstract":"<div><div>The growing development of deep geothermal energy resources, where rock masses are subjected to high temperatures and significant plastic deformation, demands constitutive models that accurately capture this complex behavior. This study presents a novel thermomechanical constitutive model within a strain-softening framework, which uniquely integrates the coupled effects of temperature (<em>T</em>), confining pressure (<em>σ</em>₃), and plastic shear strain (<em>γ</em>^p). Its primary innovation lies in explicitly formulating the cohesion (<em>c</em>), internal friction angle (<em>φ</em>), and dilation angle (<em>ψ</em>) as functions of both <em>γ</em>^p, <em>T</em> and/or <em>σ</em>₃. This nonlinear evolution function is is underpinned by systematic triaxial compression tests on thermally-treated granite specimens, which reveal that <em>c, φ</em>, and <em>ψ</em> undergo initial increasing followed by an exponential decay with increasing <em>γ</em>^p. Notably, <em>T</em> and <em>σ</em>₃ play a critical role in modulating the evolution law of these fitting parameters. The proposed model, implemented in FLAC3D via a secondary development scheme, successfully reproduces the nonlinear deformation and strain-softening behavior observed in experiments. An engineering case study demonstrates that conventional models assuming constant temperature (<em>T</em> = 25°C) underestimate radial displacements around a deep circular opening by up to 188%, compared to simulations incorporating the proposed model with a realistic nonlinear thermal field. These findings emphasize the critical importance of incorporating thermo-mechanical-plastic coupling in the design and analysis of deep geothermal environments.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103602"},"PeriodicalIF":3.9,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976970","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}

{"title":"Geothermal potential of the Czech Vienna Basin: Structural and fluid-flow dynamics of a former pull-apart basin","authors":"Samuel Rybár ,&nbsp;Michal Nemčok ,&nbsp;Lucia Ledvényiová ,&nbsp;Přemysl Kyselák ,&nbsp;Ľubomír Sliva","doi":"10.1016/j.geothermics.2026.103599","DOIUrl":"10.1016/j.geothermics.2026.103599","url":null,"abstract":"<div><div>This study investigates the geothermal potential of the Czech sector of the Vienna Basin, a region traditionally explored for hydrocarbons, through the integration of seismic and fluid data. The analysis focuses on low-temperature geothermal systems (&lt;150°C) hosted by Badenian and Sarmatian (Langhian–Serravallian) sedimentary sequences. Seismic interpretation identifies key structural features, including the Steinberg Fault Zone, serving as a recharge area, and the Lanžhot–Hrušky Fault Zone, representing a discharge area of a topography-driven geothermal fluid-flow system connected by a network of densely spaced aquifers. Hydrogeochemical analyses reveal total dissolved solids ranging from 3400 to 21,000 ppm and fluid inflow rates from 0.5 to 14.5 m³/h. Current limitations include incomplete data coverage and relatively low geothermal gradients; however, the availability of extensive hydrocarbon infrastructure and a large well database provides a unique opportunity for geothermal exploration and redevelopment. Deepening of selected wells in the most promising areas could increase reservoir temperatures, improving the economic efficiency of future geothermal projects. This study provides the first integrated structural and hydrogeothermal interpretation of the Czech sector of the Vienna Basin. The results identify a topography-driven geothermal circulation system controlled by the Steinberg and Lanžhot–Hrušky Fault Zones, linking recharge and discharge zones across multiple Badenian and Sarmatian aquifers. These findings establish a well-constrained conceptual framework for the basin’s geothermal system and demonstrate the potential for direct-use applications based on existing exploration data.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103599"},"PeriodicalIF":3.9,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976971","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}

{"title":"Hydrogeochemical characteristics and geological controls of thermal springs in the Chengde Area, North China","authors":"Yixuan Wang ,&nbsp;Xun Zhou ,&nbsp;Jingru Ma ,&nbsp;Bin Fang ,&nbsp;Ye Shen ,&nbsp;Ruige Chen ,&nbsp;Yanqiu Wu ,&nbsp;Yanxiang Shi ,&nbsp;Mengying Chen ,&nbsp;Qiqi Liu ,&nbsp;Tong Zhang ,&nbsp;Guangbin Tao ,&nbsp;Linyang Zhuo","doi":"10.1016/j.geothermics.2026.103600","DOIUrl":"10.1016/j.geothermics.2026.103600","url":null,"abstract":"<div><div>Hot springs in the Chengde region of northern Hebei Province, China, occur in scattered locations influenced by varied geological structures. Twenty-eight water samples from 10 sites were analyzed to investigate hydrogeochemistry and geothermal behavior. Stable isotopes indicate meteoric recharge at elevations of 861–1938 m, with northern springs near active faults showing more depleted signatures, reflecting deeper circulation. The waters are weakly alkaline, low- to moderate-TDS, and mainly HCO₃·SO₄–Na and HCO₃–Na types. Na⁺ derives from silicate weathering and cation exchange, SO₄^2- from evaporite dissolution and pyrite oxidation, and HCO₃^- from CO₂-driven carbonate dissolution. Trace elements (Li, Rb, Cs, Sr, Ba) vary systematically among groups, indicating differences in reservoir lithology and circulation depth; carbonate dissolution is a major Sr and Ba source. Mineral saturation and ion concentrations reflect contrasting water–rock interaction intensities. Reservoir temperatures from silica geothermometers and the SiO₂–enthalpy model range from 50 to 143 °C, with circulation depths up to approximately 4500 m and cold water mixing ratios of 46–93%. Springs linked to faults and lithological contacts generally have higher temperatures and deeper flow paths, whereas those in bedrock fractures are shallower and more affected by mixing. These findings highlight the combined influence of topography, geological structure, and lithology on geothermal circulation, providing a geochemical framework for geothermal exploration and resource assessment in intracontinental regions.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103600"},"PeriodicalIF":3.9,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976968","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}

{"title":"Tripping and staging into geothermal wells while assuring thermal protection of downhole tools and sensors","authors":"Yifan Zhang,&nbsp;Pradeepkumar Ashok,&nbsp;Dongmei Chen,&nbsp;Eric van Oort","doi":"10.1016/j.geothermics.2026.103598","DOIUrl":"10.1016/j.geothermics.2026.103598","url":null,"abstract":"<div><div>Drilling and other well construction operations in high-temperature geothermal wells face a fundamental challenge: preventing downhole tool failure caused by exceeding temperature limits. Tripping into such wells needs to be staged to lower the possibility of thermal tool damage. This study investigates the bottomhole assembly (BHA) temperature evolution, cooling effectiveness, and operational design of staged trip-in practices in geothermal and other high-temperature wells. A thermo-hydraulic modeling framework is developed, combining a full-well finite volume model (FVM) with a lumped BHA-wellbore model, to capture transient well thermodynamics during drilling and staged trip-in operations. Model validation using Utah Forge Well 16B(78)-32 data shows that the root mean square error (RMSE) of bit/BHA temperature prediction ranges from 4°F (2.2°C) to 8°F (4.4°C). Sensitivity analyses demonstrate that the maximum stage length remains under 4-5 stands when tripping into wellbores with near-field formation temperatures in the range of 250°F (121°C) to 320°F (160°C) unless significant well geometry or mud property changes occur. The only strategy that consistently extends downhole sensor survivability beyond 8-10 stands is BHA external thermal insulation. Simulation results demonstrate that adding a field-proven 0.15 in (3.8 mm) coating with thermal conductivity of 9 BTU.in/hr/ft²/°F (1.30 W/m/K) can reduce BHA temperatures by up to 30°F (17°C), compared to unprotected configurations under these downhole conditions. The modeling and analysis can also help identify scenarios where staged circulation is insufficient and continuous circulation (i.e., circulation while making connections) is required to maintain safe tripping BHA temperatures. These findings provide practical and insightful guidance for the design of effective cooling strategies during geothermal and high-temperature oil and gas well drilling and tripping operations, ensuring safer and more efficient operations in extreme downhole thermal environments with a lowered risk of BHA component failure.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103598"},"PeriodicalIF":3.9,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925309","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}

{"title":"Fracture properties, structural heterogeneity, and permeability in the Þeistareykir geothermal system, NE Iceland","authors":"Aastha ,&nbsp;Emma Bramham ,&nbsp;Andy Nowacki ,&nbsp;Nick Shaw ,&nbsp;Anette Mortensen ,&nbsp;David Healy","doi":"10.1016/j.geothermics.2026.103596","DOIUrl":"10.1016/j.geothermics.2026.103596","url":null,"abstract":"<div><div>Permeability in the Þeistareykir geothermal system of Iceland is structurally controlled. Natural fracture networks are abundant in Þeistareykir and contribute significantly to fluid flow. Understanding which features enhance permeability and hydraulic conductivity, and how their properties interact with lithology and reservoir structure, is key to predicting reservoir behaviour. To address this, we utilise a range of borehole data to characterise natural fractures in terms of their occurrence, orientation, relative distribution, their relationship with the major lithological units and permeable flow zones in the subsurface. Results show systematic variations in fracture density, thickness, and distribution pattern across different lithologies and depths, with orientations ranging from NNW-SSE, N-S, NNE-SSW to NE-SW. Fractures exhibit the highest intensity in the deeper acidic intrusive units or coarser grained basalt with a predominant N-S-trend and bimodal dip distribution. However, permeability is controlled by a complex interplay of fracture geometry, openness and connectivity rather than simply high fracture abundance or a preferential set of fractures. Permeable feed zones show diverse structural expressions, ranging from high-density fracture clusters and large-aperture fractures to intensely fractured damage zones and multiple intersecting fracture sets. These findings demonstrate that the structural character of the potential fluid-flow channels is highly variable in Þeistareykir. The results of this study can be incorporated into fracture and flow models to enhance our understanding of the permeability distribution and fluid pathways in the Þeistareykir geothermal system.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"136 ","pages":"Article 103596"},"PeriodicalIF":3.9,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925306","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}