Nemrut Volcano, which surfaces in the north of Bitlis province in Türkiye, is one of the most important active members of the Quaternary volcano sequence in Eastern Anatolia. 

According to historical records, the last volcanic activity in the region was in 1441 in the north of Nemrut Caldera and the basalt flows formed as a result of this volcanic activity caused Nemrut to be one of the last known active stratavolcano volcanoes in Turkey. It is possible to talk about a formation mechanism in which the intense tectonism in Eastern Anatolia is also effective.

Nemrut Caldera, which has a surface area of approximately 36 km², has a total of 5 lake formations, two of which are large, and Lake Nemrut is known as the second largest caldera lake in the world. Water temperatures in the lakes in the caldera vary between 16-41 ⁰C. Hot water and gas outflows are observed in and around the caldera, which makes the region interesting for both geoscientists and geothermal energy investors. Due to the volcanic activity extending towards the north-east, there are hot water springs formed due to volcanism on the shore of Lake Van in the east of the region. 

The potential for geothermal energy applications in the region is still being investigated. In this context, the surface geology of the caldera and its surroundings was analysed and a series of hydrogeochemical investigations were carried out by taking samples from the hot and cold waters in and around the caldera and evaluating some critical elements. According to the results of chemical analyses and isotope analyses, since the hot-cold water mixture is intensely observed in the region, an exploration drilling to be carried out at the correct location in the region is also important in terms of understanding the reservoir levels and conditions.

How to cite: Tut Haklıdır, F., Şengün Çetin, R., and Görgülü, İ. S.: Geothermal exploration in the Nemrut Caldera and surroundings (Eastern Anatolia-Turkey): Trying to unlock of geothermal potential in one of the world's largest calderas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3906, https://doi.org/10.5194/egusphere-egu24-3906, 2024.

Hot fluid-rock interactions in volcanic-hosted geothermal systems favour the presence of hydrothermal alteration patterns conforming the clay cap, dominated by argillic alteration, and the propylitic zone, currently related to the geothermal reservoir. Clay minerals are ubiquitous phases in these geothermal systems, being the reaction progress from trioctahedral smectite to chlorite, via chlorite/smectite (C/S), and dioctahedral smectite to illite, via illite to smectite (I/S), typical indicators of evolution from clay cap to reservoir conditions with increasing temperature. In fact, different geothermometers have been proposed using chlorite composition highlighting the relevance of clay minerals for a complete understanding of hydrothermal pathways in active geothermal systems.

Here, we analyse clay minerals (petrography, XRD, SEM-EDX and HR-TEM-EDX) from a 1000.87 m deep exploration drill core in the active Nevados de Chillán Geothemal System (NChGS) in Southern Volcanic Zone (central Chile). Lithologies are dominated by andesitic lavas and volcaniclastic breccias. Based on hydrothermal mineral assemblages, a transition from argillic to sub-propylitic (c. 350 m deep), beginning the propylitic alteration zone at 680 m deep has been defined. In situ temperature measurements during drilling achieve values up to 200°C at the bottom of the well. Geophysical and geochemical approach suggest a geothermal reservoir at c. 1200 m deep, with temperatures around 250°C, hosted in fractured granitoids.

XRD of clay minerals include C/S, corrensite, chlorite, I/S and illite, with a decrease of C/S and I/S with depth. Based on SEM morphologies and sizes, two types of chlorites have been defined: Chl-1, systematically present along all the core and paragenetic with quartz+albite+calcite, characterized by grain size (10-40 mm) and Chl-2, mostly observed as fine-grained flakes (average grain size ~4 mm), only identified in deeper samples, in association with laumontite+epidote±prehnite and rare Ca-garnet. SEM-EDX analyses in Chl-1 suggest an increase in Mg with depth, contrasting with the reverse observed pattern in Chl-2, which is Fe-richer compared with Chl-1. HR-TEM of selected samples at different depths confirms (1) the presence of the Fe-richest chlorites at the shallow levels and a general Mg increase with depth, and (2) the presence of C/S along the core. Cathelineau’s geothermometers using SEM-EDX data provides temperatures of 170-220°C for Chl-1 and 220-240°C for Chl-2, consistent with in situ measured temperatures. However, HR-TEM-EDX chlorite data with (K+Na+Ca)<0.1 apfu provide a rather dispersion in the Inoue et al. (2018) geothermometer, with a progressive T increase from the upper sample (275±48°C) to the deepest one (312±69°C).

The presence of different types of chlorites in the NChGS is interpreted as consequence of different alteration patterns. Chl-1 is associated with a previous regional event meanwhile Chl-2 would be formed during the geothermal alteration stage. HR-TEM data also highlight the disequilibrium existing during geothermal alteration event, probably because the high fluid/rock ratio and the short time for mineral precipitation. Under these disequilibrium conditions, the application of chlorite chemistry-based geothermometers must be only considered as indicator of temperature rather as a precise way to define the real reservoir conditions.

Acknowledgments: ANID-FONDECYT Project 1220729 and Andean Geothermal Center of Excellence (CEGA).

How to cite: Morata, D., Maza, S., Abad, I., Cuevas, C., and Arancibia, G.: Understanding hydrothermal alteration pathways in active geothermal systems: a look from clay mineralogy on the Chilean Andes Nevados de Chillán Geothermal System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9017, https://doi.org/10.5194/egusphere-egu24-9017, 2024.

Time lapse gravity measurements can give information on underground mass redistribution. Observations are especially valuable over the course of subsurface use, for instance during geothermal exploration of an area. To monitor the mass transfer of underground geothermal fluids associated with the harnessing of a hydrothermal system and to assess its long-term sustainability, we have performed long-term observations at Theistareykir (Icelandic North volcanic zone).

In this study, we model the mass and fluid displacement through the use of the hybrid gravimetry technique. Hybrid gravimetry is a method which consists of the combination of several complementary gravity observations. At Theistareykir, the following experiments are collecting data since 2017:

• micro-gravity time lapse relative measurements are repeated yearly on a pre-designed network of points;
• relative gravity measurements are recorded continuously at several multi-parameter stations deployed within and outside the geothermal area. Each station is equipped with a superconducting or a spring gravimeter as well as a GNSS receiver, a broadband seismometer and hydrological and weather sensors.
• absolute gravity measurements are collected yearly, to constrain the instrumental drift of the relative gravimeters.

Here, we present the complete time series recorded by two superconducting gravity meters at Theistareykir since 2017. Gravity changes associated with potential vertical displacements of the continuous gravity meters are obtained from GNSS data, and removed from the raw data. Similar reductions are performed for other contributions from the meteorological data (pressure, snow height). The reduced time series have been used to obtain an accurate local Earth tide model. Such model is subtracted from the continuous gravity records in order to obtain the gravity residual, sensitive to the geothermal activities (injection, extraction).

From the analysis of the gravity time series we notice gravity decrease at the production site. This trend is also visible from the time lapse gravity changes maps, obtained by the integration of micro-gravity data with ground displacement data. Patterns from the spatial maps of gravity changes show gravity increase southwards of the injection area, suggesting drainage of the injected water along the Tjamaras fault. The modelling results are compared with mass changes estimated from the injection and production rates, provided by Landsvirkjun, the operating energy company, thereby constraining the interpretation.

Ongoing work encompasses forward modelling approaches to quantify mass transfers (extraction, injection, recharge, atmospheric losses) within the geothermal system.

How to cite: Giuliante, B., Jousset, P., Krawczyk, C., Hinderer, J., Riccardi, U., Portier, N., Forster, F., and Mortensen, A. K.: Subsurface mass modelling at Theistareykir geothermal field, Iceland, using hybrid gravimetry., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19542, https://doi.org/10.5194/egusphere-egu24-19542, 2024.

In Germany, the geothermal development takes place at different speeds regionally. Compared to the Molasse Basin in South Germany, the North German Basin is just at the beginning of its geothermal exploration.

The project “Warm-Up” aims to evaluate the geothermal potential in the North German Basin and to promote its geothermal development. One target for detailed investigations are the sandstones of the Dogger. This Jurassic reservoir with nearly full extent in the North German Basin was a worthwhile target for the Oil Industry based on its reservoir quality and its oil content. A large volume of data, including geological and lithological one, with special focus on hydraulic data, porosity-permeability relationships and their links to the facies have been evaluated. Where core data is not available, the extraction of hydraulic properties from well logs is necessary. Different methods for deriving porosity and permeability from well logs are tested and checked against core data. If hydraulic test results are available the comparison of those in-situ data to logging and core measurements is of crucial importance. In reality, a full set of logging, core and test data is only available in a few wells, despite the large effort, taken by the hydrocarbon industry in the past. Therefore, it is important to develop workflows, that allows the prediction of the productivity of the Dogger sandstones in areas with fewer data and to reduce the exploitation risk. Companies like local municipal utility or majors can utilize this knowledge to unlock the geothermal potential of the North German Basin.

How to cite: Weber, I. and Tischner, T.: Using Oil & Gas Borehole Data to Unlock the Geothermal Potential of the Dogger Sandstone in the North German Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5413, https://doi.org/10.5194/egusphere-egu24-5413, 2024.

Understanding the controls on crustal fluid-flow in geothermal fractured reservoirs is critical to assessing their occurrence and storage capacity. The Nevados de Chillán Geothermal System (NChGS), located in Southern Chilean Andes, is hosted in volcanic-volcaniclastic rocks and fractured granitoids. In this work, we present evidence of how regional to local fault and fracture networks control the location and size of the NChGS.

Fractures in crystalline rocks were analyzed in three sites: 1) Shangri-La diorite, 2) Las Trancas granodiorite and 3) Valle Hermoso hornfels. Linear scanlines have a total cumulative length of 130 meters, in which >1000 fractures were measured. Results show preferential fracture orientations of N60E, N30E, and N45E for the three sites, respectively. Minor families of fractures in NNW and NW directions are also observed. The intensity of fractures (i.e. number of fractures/scanline length) is ~5m^-1 at Shangri-La and exhibits minimum and maximum values between 6-13m^-1 at Las Trancas, and between 8-13m^-1 at Valle Hermoso. Variability in fracture intensity relates to profile orientation, presence of localized shear zones or distance from the geothermal system. These outcrop-scale structures are consistent with regional geometric arrangement and kinematics of major faults.

A fourth site was analyzed in the Las Termas-Olla de Mote area. Here, Miocene volcanic and volcaniclastic rocks present an intense argillic alteration in an area ca. 1 km². Numerous surface geothermal manifestations, such as fumaroles, hot springs, mud pools, mud volcanoes, and heated soils, can be observed. Using a Hanna HI 98509 thermocouple and Fluke TiS45 infrared camera, surface temperatures between 13°C and 95°C were measured. In this site, 85 fractures were measured in a 3-meter-long scanline in a localized cataclastic shear zone. The fracture alignment is essentially isotropic with an intensity of ~28m^-1. We noted a hydrothermal alteration pattern associated with centimetric to metric fault planes and fault zones. X-Ray Diffraction on clay minerals related to these fault-controlled alteration zones shows high-crystalline illite (Kübler index as low as 0.096) and kaolinite (Aparicio-Galan-Ferrer index as high as 1.115).

Numerical modeling, considering structural, hydrothermal and temperature data, was performed with COMSOL Multiphysics, which allowed us to demonstrate the control of fractures in the development of a crystalline rock hosted geothermal reservoir. The simulated reservoir isothermal pattern can be reproduced consistently with our conceptual geological model after 15 ka.

These combined results evidence the first order structural control on the formation of the NChGS. Intersection of regional fault/fracture systems and local dilation areas are the main controls that permit the formation and growth of the active geothermal system. Moreover, the high crystallinity fault-related illite and kaolinite confirms that fluid-flow is mainly controlled by secondary structural permeability. Finally, the surface temperature data, coupled with thermal numerical modelling, allow us to establish a comprehensive theoretical model for the active NChGS relevant for sustainable exploitation.

This work is a contribution to the ANID-FONDECYT Project 1220729 and Andean Geothermal Center of Excellence (CEGA). Valentina Mura thanks to ANID -Beca Doctorado Nacional 21210890. 

How to cite: Arancibia, G., Mura, V., López-Contreras, C., Oyarzo, I., Browning, J., Healy, D., Maza, S., and Morata, D.: Fluid flow in the Nevados de Chillán Geothermal System as an example of fractured reservoir, Southern Andes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10911, https://doi.org/10.5194/egusphere-egu24-10911, 2024.

Located in the northwest of Canary Islands, La Palma is one of the most volcanically active islands in the archipelago. The island experienced a volcanic eruption from 19 September to 13 December 2021, which had significant social, economic, and scientific impacts. This event serves as a reminder of the island's potential as a host for geothermal resources. Therefore, geochemical prospection of soil gases at Cumbre Vieja can provide valuable information for investigating the presence of permeable areas and potential upflow for degassing of geothermal systems at depth. This study was carried out between July and September 2023 and presents the results of a soil gas study located southwest of the 2021 lava flow. The survey aimed to identify permeable areas by conducting in-situ measurements of diffuse CO₂ emissions and sampling and analyzing CO₂ concentration and isotopic composition (δ¹³C-CO₂). A total of 766 sampling sites were selected over an area of approximately 25 km², with an average distance of 100 m between sites. Soil CO₂ concentrations ranged from typical atmospheric values (≈ 400 ppm) up to 40,000 ppm. The average CO₂ concentration measured was 1,700 ppm. The δ¹³C-CO₂ isotopic composition revealed the presence of three distinct end-members: biogenic, atmospheric and deep-seated CO₂, defined by isotopic compositions of 25‰>δ¹³C-CO₂>-15‰, -8‰ and 2.1‰>δ¹³C-CO₂>-8‰ and CO₂ concentrations of 100%, 0.04% and 100%, respectively. Results show that, with a mean of -13.7‰, a minimum of -28.9‰ and a maximum of -4.8‰, CO₂ at most sampling sites is composed of various mixtures of atmospheric and biogenic CO₂, with some contributions from deep-seated CO₂. The accumulation chamber method was used to measure soil CO₂ efflux at each sampling site using a portable non-dispersive CO₂ sensor, model LICOR-Li-820. The measured CO₂ efflux values ranged from non-detectable to 160.3 g·m^-2·d^-1, with an average value of 4.7 g·m^-2·d^-1. For the estimation of the total diffuse CO₂ emission from the study area, we calculated the average of 100 sequential Gaussian simulations. This gave a value of 100.8 ± 2.8 t·d^-1, corresponding to a standardized emission rate of 4.1 t·km^-2-d^-1. The results show a significant correlation between the distribution of ²²²Rn gas activity anomalies and the highest CO₂ efflux values in the eastern part of the study area. Soil gas measurements of CO₂ concentration, isotopic ratio and efflux are a valuable and non-invasive technique for surface exploration, helping to define permeable areas and potential upflow zones of potential geothermal system structures and enabling an efficient subsequent subsurface exploration phase.

How to cite: Martín Lorenzo, A., Copete-Murillo, K., Reyes, Á., Gironés, A., Melián, G. V., Asensio-Ramos, M., Rodríguez, F., Padrón, E., Padilla, G. D., Hernández, P. A., and Pérez, N. M.: Soil gas CO2 concentration, isotopic ratio and efflux measurements for geothermal exploration in La Palma, Canary Islands., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12301, https://doi.org/10.5194/egusphere-egu24-12301, 2024.

Xiong'an New Area is located in the northern of Jizhong Depression in Bohai Bay Basin, covered by three geothermal fields: Niutuozhen, Rongcheng, and Gaoyang. Clarifying the rock physical conditions and geothermal characteristics, combined with the elements of geothermal resource accumulation (heat source, channel, reservoir, caprock, fluid), plays an important role in understanding geothermal resources.Based on heat source research, this study analyzed the temperature measurement curves of 30 drilling wells and measured data of thermal conductivity and heat generation rate of 100 rocks to analyze the geothermal gradient and distribution of geothermal flow in Xiong'an New Area. The results showed that Xiong'an New Area has a high geothermal background, with geothermal flow ranging from 53.3mW · m^-2 to 106.5mW · m^-2, with an average value of 73mW · m^-2. It is higher than the average heat flow value of 63.0 ± 24.2mW · m^-2 in China Mainland, and belongs to high abnormal area. The geothermal gradient of caprocks is around 35 ℃/km, slightly higher than that of the Mesozoic and Cenozoic fault basins in Eastern China. Based on the geothermal field, combined with the characteristics of heat sources, reservoirs, and channels of deep geothermal resources, a genetic model of geothermal resources in Xiong'an New Area is established. It is considered that the reservoir-cap assemblages composed of the Cenozoic caprocks and the Proterozoic carbonate rocks in Xiong'an New Area, the alternating structural pattern of uplift and sag, and fluid activity affect the occurrence of deep geothermal resources. The geothermal resources are prone to enrichment in uplifted structures controlled by faults or in low uplifted Proterozoic thermal reservoirs. The high-value of geothermal flow, high permeability reservoirs, and regional continuous caprocks are favorable areas for geothermal development.

How to cite: Guo, S., Cui, Y., and Tang, B.: Present geothermal field characteristics and its influencing factors in Xiong'an New Area , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9278, https://doi.org/10.5194/egusphere-egu24-9278, 2024.

Energy request from renewable sources is increasing due to high energy demand and the need of a more sustainable use of the resources. Among renewable sources, geothermal energy represents a powerful tool to reduce the energy dependence on fossils contributing to reducing the impact of climate change.

Despite its high potential, geothermal energy has historically had a limited role in Italy, confined to the well known Tuscany areas, although it could have a more widespread exploitation satisfying local energy demands through both direct and indirect uses.

The Emotion Project (GeochEMical characterization of geOThermal manifestations in Italy and development of the natIONal geothermal fluid web portal) is a three-year broad-scope project (2023-2025) funded by the Italian Ministry of University and Research in the framework of ten-year INGV PIANETA DINAMICO Research-Program (https://progetti.ingv.it/it/emotion).

The ambition of EMOTION project is to accelerate the geothermal exploration for low, medium and high temperature (enthalpy) resources by a detailed geochemical characterization of the manifestations of geothermal interest located in central-northern Italy and to develop a solid and public web portal of all Italian geothermal manifestations, including those already studied in the central-southern part of the country (Vigor Project).

Here we present first year results obtained by a detailed critical review of available geochemical information on thermal springs, mineral waters and gas emissions. These data represent the starting point to identify interesting and data-missing areas to be further investigated by new geochemical campaigns planned for 2024. Eleven Italian Regions were investigated (Tuscany, Umbria, Marches, Emilia Romagna, Liguria, Piedmont, Aosta Valley, Lombardy, Trentino Alto Adige, Veneto and Friuli Venezia Giulia) by a research team belonging to INGV, University of Florence, Perugia, Genoa and Calabria. The review data were collected from scientific papers, unpublished theses, regional datasets, reports and well logs (e.g., AGIP), other web portals and unpublished data.

More than 4000 fluid manifestation information, among which thermal and cold springs, wells, bubbling polls, dry vents and fumaroles were collected and organized in a database, as homogeneous as possible. The database includes geographical data, geochemical analysis of major, minor, trace ad isotopic species, physics-chemical parameters and information on water table level and flow rate.

To get hints on reservoir temperatures, chemical-physical processes ruling fluid circulation and to discriminate manifestations of geothermal interest from the others, a selection was made considering specific criteria, proposing also a first approach to standardizing geochemical data, potentially useful in the framework of opening and sharing scientific data.

How to cite: Cantucci Marini, B., Procesi, M., Tassi, F., Cardellini, C., Apollaro, C., Rouwet, D., Zorzi, F., Vespasiano, G., Bagnato, E., Tamburello, G., Venturi, S., Cinti, D., and Belmonte, D.: The Emotion Project:  improvement of the geochemical knowledge on geothermal manifestations in Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15521, https://doi.org/10.5194/egusphere-egu24-15521, 2024.

GeoLaB (Geothermal Laboratory in the Crystalline Basement) started in the beginning of 2023 to plan and build an underground geoscientific laboratory in a fractured crystalline basement. One of the potential selected sites is the Odenwald complex (Hessen, Germany) due to its geology (fractured crystalline basement) and petrology (Tromm granite). Considerable efforts and investigations were recently implemented to evaluate, whether this site is a suitable location for the realization of GeoLaB.

In the initial exploration stage, surface rock samples were collected in the Odenwald (Streitsdöll, Hammelbach and Ober-Mengelbach) area for mineral and petrological investigations. The sampling strategy aims for different structural contexts within the same lithology, e.g. a non-fractured granite, one located in the fault damage zone, and one located in the cataclastic core zone. The rock samples are macroscopically characterized by well-formed feldspar/plagioclase and mica (biotite/muscovite). Mineralogy and petrology are fundamental for investigating the composition and the occurrence of hydrothermal alteration. This influences rock properties such as porosity-permeability and also the response to applied stress.

A first set of eight samples was investigated by means of X-ray powder diffraction XRD (quantitative estimation of the mineral assemblage, rock classification), electron microprobe analyzer EMP (determination of the mineral geochemistry, hydrothermal alteration and microstructures) and X-ray fluorescence XRF (whole chemistry and trace elements). The granites/granodiorites are composed of quartz, plagioclase, felspar (andesine based on the Na-Ca geochemistry), and mica (biotite and muscovite). Apatite, magnetite, rutile and monazite were detected as accessories, thus enabling geochemical dating.

Three samples (Streitsdöll) show hydrothermal alterations in the form of kaolinite or clay phases with similar mineral chemistry Al₂Si₂O₅(OH)₄ at the plagioclase rims. Traces of metasomatic processes could be observed in the images acquired with the EMP. The quantitative mineral assemblage evaluation also indicated different types of plutonic rocks: granodiorite and granite based on the QAPF (Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid)) diagram. A compositional variation with depth can be expected based on the mineral heterogeneity. This hypothesis will be verified by analyzing cores samples from exploration drillings planned for 2024.

Besides seismic and geophysical campaigns, additional fieldwork focusing on structural geology, rock sampling, and geomechanical experiments will be conducted to develop a baseline to scientifically assess whether the Odenwald site is a suitable location to build the GeoLaB.

Keywords:

underground laboratory, crystalline basement, fractured granite, mineral composition variation, hydrothermal alteration.

How to cite: Deon, F., Sass, I., Bossennec, C., Loges, A., Appelt, O., Seib, L., Milsch, H., and Zimmermann, G.: Mineralogical and petrological assessment of selected granites and granodiorites from the Odenwald area, Germany: a crucial step toward the site selection for the GeoLaB underground infrastructure?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6049, https://doi.org/10.5194/egusphere-egu24-6049, 2024.

New Zealand has abundant geothermal resources which produce ~20% of the country’s electricity. Most geothermal systems are located in the geologically complex rifting arc of the Taupō Volcanic Zone (TVZ), along the Australian/Pacific plate boundary. The TVZ is one of the most geothermally active regions on Earth, discharging ~4200 GW of heat through 23 high-temperature systems. Understanding the regional-scale factors influencing the locations of the geothermal systems is important for exploration and sustainable exploitation.

There are several intriguing correlations between TVZ geology and geothermal system locations. Over two-thirds of geothermal systems occur near inferred caldera margins. Many geothermal systems rise to the surface beneath topographic lows. Geothermal activity forms two NE-SW trending zones of low resistivity which are separated by the densely faulted and geothermally quiescent Taupo Fault Belt; most of the geothermal systems are not associated with any known major faults. We can gain new insights into these potential relationships by merging increasingly extensive geophysical and geological surveys of the central North Island of New Zealand into numerical flow models.

We created generalised numerical models of heat and fluid flow using TOUGH2 software to explore large-scale influences on geothermal circulation in the TVZ. Locations of over half the modelled geothermal systems can be broadly explained by the effects of topographic loading due to water table variations. Locations are further improved when topographic effects are combined with localised heat sources at depth inferred from magnetotelluric models. At three geothermal systems, influences such as more permeable volcano-sedimentary cover or a region of intense faulting that acts as a recharge zone for cold downwelling fluid also seem to be important. Three systems (Ohaaki, Te Kopia and Orakei Korako) cannot be explained with any of our models but are known to be in areas with significant local geological structures, making them interesting targets for future studies.

How to cite: Pearson-Grant, S., Bertrand, E., Miller, C., and Carson, L.: Distribution of geothermal resources in New Zealand: insights from geophysics and numerical modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7014, https://doi.org/10.5194/egusphere-egu24-7014, 2024.

High-quality maps of the geothermal gradient and temperature are essential when assessing the geothermal potential of a region. However, determining geothermal potential is a challenge when direct measurements of in situ temperature and thermal property information are sparse, as is the case in Ireland. In addition, individual geophysical methods are sensitive to a range of parameters, not solely temperature. We develop a novel approach to determine the geothermal gradient using a joint geophysical-petrological thermochemical inversion (Chambers et al. Tectonophysics (2023) & Fullea et al. GJI (2021)), which requires seismic surface wave data, thermal property data, and additional geophysical and petrophysical datasets. The multi-parameter models produced by the integrated inversions fit the surface-wave, heat flow and additional data, revealing the temperature, lithospheric structure and geothermal gradient within the crust and mantle.

Here we present the new methodology and resulting models of Ireland’s subsurface temperature with a focus on new thermal conductivity measurements and their impact on temperature. A new map of thermal conductivity (TC) for all of Ireland was generated using all existing measurements of thermal conductivity, in addition to 609 new measurements from the optical scanning technique and 86 using the Divided Bar Apparatus (DB) which we use in the inversion. Our new methodology produces results comparable to past temperature and geophysical measurements and models. Importantly, the maps are within error of direct borehole temperature measurements, providing confidence in the results. Lithospheric and crustal thickness play a key control on the temperature gradient with areas of thinner lithosphere resulting in elevated geotherms. In some locations, we observe geotherms elevated beyond expectations which result from high radiogenic heat production from granitic and muddy limestone rocks. This new methodology provides a robust workflow for determining the geothermal potential in areas with limited direct measurements. The final temperature model updates previous maps of Ireland and will be used for future geothermal exploration and utilisation.

How to cite: Chambers, E. L., Kiyan, D., Pasquali, R., Fullea, J., Meere, P., Lebedev, S., Bean, C., and O'Reilly, B.: Mapping thermal conductivity in Ireland to determine geothermal potential, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8152, https://doi.org/10.5194/egusphere-egu24-8152, 2024.

The geothermal energy in the northern Jianghan Basin is considered hydrothermal geothermal resources. Heat generation condition and thermal conduction mechanism are crucial factors affecting the migration of geothermal fluid. However, it is not clear about the controlling factors of geothermal distribution and formation modes in this region. To explore the spread, accumulation and preservation characteristics of geothermal resource in the northern Jianghan basin, the deep geological backgrounds and tectonic characteristics of the target area are analyzed. Also, the genetic model is conceived during the research to have a acquaintance with the process of geothermal energy evolution. Traditional methods, for example the inversion of gravity, magnetic, and electric, are applied to recognize the concealed rock. Besides, numerous data, including seismic, oil and gas wells, geothermal wells and hydrochemical composition, is used to analyze the characteristics of geothermal fields, properties of deep rock mass, structures of geothermal reservoirs and thermal conductivity of faults. The results show that the regional uplifts and depressions control the distribution of geothermal resources. In addition, what play a pivotal role in the connection between deep heat sources and upper prospecting reservoirs are boundary faults of the basin. What’s more, neotectonic activities of faults are beneficial channels for heat and water conduction. On the basis of above researches, the model of geothermal distribution related with fault systems is well established, confirming that geothermal resources are mostly distributed in conjunction zones of differed faults. The findings of this work provide scientific evidence for discovering other geothermal favorable areas in the Jianghan Basin.

How to cite: Wan, X., Shen, C., and Ge, X.: Characteristics and mechanism analysis of geothermal resources innorthern Jianghan Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20195, https://doi.org/10.5194/egusphere-egu24-20195, 2024.

The Yangbajing geothermal field, located in the south part of the Tibetan plateau is the largest high-temperature geothermal system of the whole plateau. Numerous hydrological, geological, and geothermal studies have been conducted to gain insights into the heat source of the geothermal system. Geothermal studies show that heat flow in this area is extremely high. However, heat flow contributed by the crustal radiogenic heating together with mantle heating still can not explain the anomalously high heat flow (~116 mW/m²) here. In this study, we use the high-resolution 3D electrical resistivity models, generated from magnetotelluric data in the Yangbajing region of southern Tibet, that image zones of enhanced conductivity in the middle crust. Such features may relate to partial melts (or magma chambers) with a melt fraction of more than 19%. Here, with the help of other available data, primarily hydrothermal and geochemical data, we estimated the heat flow generated by the partial melts in this area. Furthermore, we performed a set of simulations to reproduce the thermal evolution of the magma chambers in this region. our results indicate that the magma chambers below the study region may provide sufficient heat flow to fill the relatively large heat flow gap (~20.25 mW/m² ), apart from the mantle heat conduction and radiogenic heating for the geothermal system. In addition, the thermal evolution simulations show that the magma chambers beneath the Yangbajing geothermal system may remain relatively warm, after the long cooling procedure. Our results highlight the possible contribution of the magmatic heat generation to the Yangbajing geothermal system, and reveal that crust contributes a significant proportion of the total surface heat flow (~70.75 mW/m²) in the Yangbajing geothermal field, which is much higher when compared with the typical rift basins in China.

How to cite: Lei, L., Jin, S., Dong, H., Wei, W., Ye, G., and Zhang, L.: Investigating the Heat Source of Yangbajing Geothermal Field, South Tibet, with Magnetotelluric Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14595, https://doi.org/10.5194/egusphere-egu24-14595, 2024.

To date, the majority of geothermal projects in Germany have focused on deep geothermal systems, while resources at intermediate depths have been little explored. However, intermediate-depth geothermal systems have a high potential for heat generation, even in areas previously considered less favourable for geothermal use, and could make a significant contribution to Germany's heat supply. In order to accelerate the heat transition and to become independent of fossil fuels, the ArtemIS project aims to assess the medium-depth geothermal systems in Germany, covering all types of geological plays and providing regionalised information for different geothermal applications. To this end, profile texts will be developed containing all relevant subsurface information required for preliminary geothermal assessments, such as geological descriptions of potential geothermal reservoirs, reservoir thickness, hydraulic and thermal rock properties, and fluid chemistry. In addition, static 3D geological models are created as the basis for 2D and 3D numerical reservoir models to simulate the regional heat potential and different geothermal exploitation scenarios, including the performance of hydrothermal doublets. Machine learning algorithms will be applied to speed up the extraction and analysis of well data and to improve reservoir evaluation and economic forecasting, particularly in areas of low data density. The results will be integrated into the publicly available web platform "Geothermal Information System - GeotIS", which will provide general information, data and modelling results in a user-friendly way for non-professionals such as local communities and municipal energy suppliers. Here we present the current status and first results of the ArtemIS project.

How to cite: Weydt, L., van der Vaart, J., and Sass, I.: The ArtemIS project: Assessment for medium-depth geothermal energy utilization in Germany , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15055, https://doi.org/10.5194/egusphere-egu24-15055, 2024.

Geothermal energy has reached the front line on renewable resources assessment in recent years, especially in active volcanic areas such as the Canary Islands (Spain), and precisely in La Palma island, where a recent volcanic eruption occurred in 2021, representing a unique opportunity to carry out in situ exploration. Cost-effective geochemical surveys, like soil radon (²²²Rn) and thoron (²²⁰Rn) gases activities measurements, have demonstrated to provide relevant insights as part of surface geothermal exploration, helping to identify permeable areas and potential up-flow zones and, therefore, defining potential geothermal systems boundaries. Both radon (²²²Rn) and thoron (²²⁰Rn) are radioactive isotopes of radon gas and are derived from the natural decay of uranium (²³⁸U) and thorium (²³²Th) respectively, present in the mineralogical composition of, particularly, igneous rocks. However, ²²²Rn present a half-life of 3.8 days while ²²⁰Rn has a shorter half-life of 55 seconds. High ²²²Rn activity surface measurements are considered to be associated to deep magmatic sources of gas, providing additional value on defining high porosity and permeable zones. On the contrary, due to its ephemeral half-life, high ²²⁰Rn activity is associated to shallow soil gas sources.

A detailed and regular surface geochemical survey was carried out in an area of 25 Km² at the western side of La Palma island and southwards from the recent lava flow of Tajogaite Volcano. A total of 766 soil radon and thoron activities discrete measurements were performed (around 30 sample sites/Km²) using a SARAD radon monitor, model RTM-1688-2, connected to a stainless steel probe inserted at 40 cm depth. Data analysis and treatment showed an average ²²²Rn value of 1,056 Bq/m³, ranging from 0 to up to 27,000 Bq/m³, and an average ²²²Rn/²²⁰Rn ratio of 0.3, ranging from 0 to a maximum of 49. The spatial distribution maps has enabled to limit areas with higher values of these two variables,which might indicate zones of interest for further investigation. Higher soil ²²²Rn activity were concentrated along an specific segment of the coast line, which is coincident with the distribution of the well-known anomalous CO₂ active diffuse degassing of volcanic origin in Puerto Naos and La Bombilla, which may have played an important role in controlling the migration and transport of these trace gases towards the surface. Radon and thoron gases activities measurements have revealed to be a worthwhile and non-invasive technique for surface exploration in highly environmental-threatened areas, like La Palma, helping to provide the definition of permeable areas and potential up-flow zones of potential geothermal system structures and permitting an efficient posterior subsurface exploration phase.

How to cite: Gironés, A., Valls, A., Thompson, M., Martín, A., Pérez, N. M., Melián, G. V., Padrón, E., Padilla, G. D., Hernández, P. A., Asensio-Ramos, M., and Rodríguez, F.: Geothermal prospecting by ground radon and radon/thoron ratio measurements at La Palma, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16021, https://doi.org/10.5194/egusphere-egu24-16021, 2024.

Lithium production has increased tenfold over the past two decades and is expected to grow steadily over the next decade, driven by the rapid development of modern technologies such as mobile electronics, electric vehicles (EVs) and grid storage applications. The European Union including Germany, however, has no conventional lithium resources and is therefore geopolitically dependent on imports. As a result, unconventional resources such as lithium recovery from geothermal brines in the Upper Rhine Graben have been explored. Elevated lithium concentrations have also been reported in other regions including the North German Basin (NGB), but no resource estimates are available. Therefore, all available data for the NGB are summarized here in order to limit potential deposits. Their potential is then assessed using a probabilistic volume-based approach.

The highest concentrations are found in the Permian Rotliegend and the Zechstein Ca2 at the basin margin. Lithium concentrations can locally reach up to 600 mg/L in the Rotliegend and 300 mg/L in the Zechstein. Our resource estimates indicate that 0.08 to 5.76 Mt of lithium could be contained in the Rotliegend and an additional 0.06 to 3.06 Mt in the Zechstein. Elevated lithium concentrations have also been reported in the overlying Triassic Buntsandstein deposits that occur over much of the basin. Values of up to 200 mg/L lithium have been detected, which we estimate to be between 0.2 and 3.48 Mt of lithium.

On the one hand, our study shows that there are sufficient domestic lithium resources in geothermal waters. However, it is also clear that the most promising resources are associated with deep, low-permeability Permian deposits that inhibit conventional (non-engineered) hydrothermal geothermal energy production. It is therefore unclear whether geothermal energy production and lithium exploration can co-exist and further studies are needed to analyze the local, onsite potential. Our study provides the starting point for this analysis.

How to cite: Alms, K., Groeneweg, A., and Heinelt, M.: Lithium prospectivity and capacity assessment in the North German Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16282, https://doi.org/10.5194/egusphere-egu24-16282, 2024.

Geothermal energy represents an important aspect of the ongoing green transition; therefore, geothermal reservoirs have to be properly investigated and studied in many and different aspects. In this frame, the Larderello geothermal field represents an important energy resource for the Tuscan region, and the first geothermal reservoir to be used for energy production. It is a vapor-dominated reservoir producing superheated steam and characterized by areas where the permeable formations of the shallower reservoir outcrops, with thermal manifestations at the surface, such as fumaroles and steaming-ground. In particular, the Le Biancane area, one of the main outcropping zones, represents a potential recharge point where meteoric water can infiltrate through the carbonate-anhydrite formations of the Tuscan Nappe.

Although the Larderello geothermal system has been studied since the beginning of the last century, a detailed and systematic investigation of the recharge in the infiltration potential areas is still missing. Indeed, only few chemical and isotopic data of meteoric waters and geothermal fluids in the Le Biancane area are available. These are not enough to give information on the main infiltration areas and origin of the geothermal fluids, considering also the re-injection of spent fluids that has been introduced since the ’70 in some of the wells. Therefore, with the aim to analyse in detail the recharge in the Le Biancane area, 11 fumaroles and 37 cold and thermal springs were sampled. In order to be able to well define the isotopic marker of this area, the investigated springs were selected on a wider area surrounding Le Biancane, on a regional scale. Two sampling campaigns have been carried out, one after the rainy season in May/June 2023 and one after the dry season in October 2023.

From isotopic analyses on fumarole condensates, differences in δD and δ¹⁸O were evident highlighting the possibility that these fluids undergo different processes before reaching the surface. Furthermore, fumaroles were analysed, among the many components, also for COS, which represents a new potential geo-indicator. On the other hand, regarding the water recharge investigation, in this work we will present the results of the isotopic hydrological approach on the spring samples.  

How to cite: Dallara, E., Lelli, M., Fulignati, P., and Gioncada, A.: New insights on the meteoric recharge at the Le Biancane area (Larderello geothermal system) from fluid geochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19591, https://doi.org/10.5194/egusphere-egu24-19591, 2024.

The IDDP-2 well at Reykjanes was drilled by Iceland Drilling Ltd. for HS Orka Ltd. in 2016 and 2017. The well was drilled as part of the Iceland Deep Drilling Project (IDDP), which aim has been to drill deep wells down to 4–5 km depth into geothermal systems in Iceland, involved casing and deepening the production well RN-15 from 2507 m to 4659 m.  Deepening of the well commenced on August 11^th, 2016, and it was completed on January 25^th, 2017. The most recent well test of RN-15/IDDP-2 was on 5^th of May 2022. The well has a casing damage just below 2300 m depth, which hinders any logging below that depth. The main feed zones are probably at the depth of the casing damage (where the main feed zone of RN-15 was located) and at about 3400 m, but there may also be a minor feed zone near the bottom of the well. When the well is opened for discharge, fluid from these feed zones enters the wellbore, flows up the well and eventually reaches a boiling point. The fluid is then two-phase with a gradually increasing steam fraction up to the wellhead. The estimated enthalpy of the discharged fluid is from about 1107 kJ/kg to 1120 kJ/kg and the steam fraction is about 30%. The production from the well was 19.2 kg/s and 22.2 kg/s at wellhead pressure 13.5 bar-g and 7.8 bar-g, respectively. The estimated productivity index is 1.4 (kg/s)/bar, which indicates low-permeability feed zones.

The geothermometry of the collected fluid sample suggests a slightly higher reservoir temperature of 294°C compared to 290°C in 2016. Note that this difference is within analytical uncertainty for SiO₂ analysis. The highest gas content measured during this study was 1.83 wt% and is higher than most of the RN wells. The deep fluid feeding the well is more diluted comparing to the fluid from RN-15 pre-2016. Most of the major non-volatiles are in a low range of the concentrations calculated for the Reykjanes reservoir. The RN-15/IDDP-2 aquifer is, however, enriched in volatiles such as CO₂, H₂S, N₂, and H₂ compared to their content during monitoring or RN-15 in 2004-2016. In general, the temperature and the composition suggest that fluid entering the well is not only sourced from 2300 m aquifer but also from deeper feed zones. 

The IDDP-2 was funded by HS Orka, LV, OR and OS, in Iceland, together with Equinor (former Statoil). The IDDP-2 also received funding from the EU H2020 (DEEPEGS grant no.690771) for all parts of the operation, and ICDP and US NSF (grant No.05076725) for spot coring and part of the related research

How to cite: Galeczka, I., Óskarsson, F., and Gebrehiwot Mesfin, K.: The chemical composition of the discharged fluid from IDDP-2, Reykjanes, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16639, https://doi.org/10.5194/egusphere-egu24-16639, 2024.

Hot water springs are typical surface manifestations of a geothermal system, especially in low enthalpy, amagmatic systems. In many of these systems, numerous cold-water springs are often associated with hot water springs. The smaller number of hot water springs and the wider spatial distribution between them make it difficult to perform a comprehensive study of such a geothermal system. In this case, associated cold water springs can be of particular help in understanding the hydrogeological setting of the geothermal system which is vital information for any future geothermal exploration programs.

There are 9 known hot springs in Sri Lanka, however they are spread over a larger area of the eastern lowlands of the country. On the other hand, there are over 225 known cold-water springs distributed among the hot water springs, making Sri Lanka a perfect location for a case study.

Most hot water springs are located at a great distance from their recharge zone (~ 50-100 km). With the exception of very few springs, cold water springs have short recharge to discharge distances (< 25 km). Geochemical and isotopic studies of the hot springs and the nearby cold springs show that both kinds are of the same origin and recharge at similar altitudes (> 600m). The electrical resistivity of cold-water springs is comparatively higher than that of rain and fresh surface water, but lower than that of hot water springs. This suggests that these cold spring waters also travel longer through the fault/fracture network through which hot spring waters circulate from recharge zones to discharge zones. These observations of cold-water springs show that they are also part of the geothermal system in Sri Lanka and reveal important information about the fluid flow paths of the geothermal system. The results and observations of the present study highlight the importance of cold-water springs in understanding the hydrogeological setting of a geothermal system. In addition, the new knowledge will be of significant benefit to future geothermal exploration programs, particularly in systems with a smaller number of hot water springs spread over a larger area.

How to cite: Bandara, D., Smit, J., Wohnlich, S., and Heinze, T.: Cold – water springs as integral part of geothermal systems: an example from Sri Lanka, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17431, https://doi.org/10.5194/egusphere-egu24-17431, 2024.

The Krafla geothermal system is located within a volcanic center that periodically erupts basaltic lavas, and has recently attracted an economic interest due to supercritical fluids forming near a shallow magma intrusion (~ 2 km depth). Here, we discuss new soil CO₂ flux and stable isotope data of the CO₂ efflux (δ¹³C) and hydrothermal calcites (δ¹³C, δ¹⁸O) of drill cuttings to estimate both the current magmatic outgassing from soils and the thermal flows in the geothermal system. Soil CO₂ emission is controlled by tectonics, following the NNE-SSW fissure swarm direction and a WSW-ENE trend, and accounts for ~ 62.5 t d^–1. While the δ¹⁸O of the H₂O in equilibrium with deep calcites is predominantly meteoric, both the δ¹³C of the soil CO₂ efflux and of the fluids from which calcite precipitated have a clear magmatic origin, overlapping the δ¹³C estimated for the Icelandic mantle (–2.5 ± 1.1 ‰). Estimates based on the soil CO₂ emission from the southern part of the system show that these fluxes might be sustained by the ascent and depressurization of supercritical fluids with a thermal energy of ~800 MW. Such significant amount of energy might reach 1.5 GW if supercritical conditions extended below the whole investigated area. Finally, we report an increase in the soil CO₂ emission of about 3 times with respect to 14 years ago, likely due to recent changes in the fluid extracted for power production or magmatic activity. Pairing the soil CO₂ emission with stable isotopes of the efflux and calcite samples has important implications for both volcano monitoring and geothermal exploration, as it can help us to track magmatic fluid upflows and the associated thermal energy.

How to cite: Bini, G., Chiodini, G., Ricci, T., Sciarra, A., Caliro, S., Mortensen, A. K., Martini, M., Mitchell, A., Santi, A., and Costa, A.: Soil CO2 emission and stable isotopes (δ13C, δ18O) of CO2 and calcites reveal the fluid origin and thermal energy in the supercritical geothermal system of Krafla, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17923, https://doi.org/10.5194/egusphere-egu24-17923, 2024.

The UK heating sector must be decarbonised to achieve net zero targets by 2050; and geothermal energy can help to provide low carbon heat. Closed-loop geothermal systems can provide low-risk solutions via the repurposing of ex-hydrocarbon and unused geothermal exploration wells. Closed-loop, medium-deep borehole heat exchangers (MDBHEs), at depths defined from 500-1000 m, could potentially use a variety of configurations, including single U-tube, double U-tube and coaxial. U-tube MDBHEs involve one or more pipes being inserted in the borehole with heat being transferred to a chilled circulating fluid within the U-tube(s) via conduction through any grout and the borehole wall. Coaxial MDBHEs consist of a concentric central pipe being inserted within an outer pipe (often, the borehole casing). Cool fluid is circulated down the annular space, gaining heat by conduction through the outer pipe wall, before being pumped to the surface through the central pipe. This study addresses the thermal and hydraulic performance of these different configurations under a range of geological and engineering conditions. Simulations were undertaken using OpenGeoSys software to evaluate optimal configurations by minimising hydraulic (and thus parasitic power) losses, while maximising the thermal output.
Under the base case scenario at 800 m, assuming water as the circulation fluid, it was observed at the end of the 25-year simulation, with a flow rate of 5 L/s and inlet temperature of 5 °C, that single U-tube, double U-tube and coaxial configurations provide specific heat extraction rates of 32.8, 36 and 39.1 W/m, respectively. These correspond to pressure losses of 1.46 MPa, 423 kPa and 85 kPa. From the analyses, it was observed that the coaxial configuration led to the lowest pressure losses and generally maximised the thermal output. The coaxial system was then applied to a case study for the Newcastle Science Central Deep Geothermal Borehole, where there are plans to repurpose the well to c.920 m in 2024 for geothermal testing. Results indicate that a thermal power of 50 kW could be attainable for a geothermal gradient of 33.4 °C/km, rock thermal conductivity of 2.5 W/(m.K) and flow rate of 5 L/s.

How to cite: Brown, C., Kolo, I., Banks, D., and Falcone, G.: Comparing the Performance of Single U-tube, Double U-tube and Coaxial Medium-to-Deep Borehole Heat Exchangers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18004, https://doi.org/10.5194/egusphere-egu24-18004, 2024.

The Songliao Basin, situated in Northeast China, boasts a significant geothermal background evident in numerous boreholes, indicating a rich geothermal resource potential with temperatures exceeding 150℃ at depths of 5km. This study aims to elucidate the formation mechanism of high-temperature geothermal resources in the Songliao Basin, analyzing various aspects such as the thermal properties of rocks, temperature fields, terrestrial heat flow, heat source contributions, Meso-Cenozoic thermal history, deep thermal structures, and factors influencing geothermal resource formation. The research offers valuable theoretical support for the exploration and evaluation of high-temperature geothermal resources in the Songliao Basin. The research involves testing the rock thermal conductivity of 263 core samples and 99 outcrop samples, as well as the rock heat generation rate of 80 core samples and 56 outcrop samples from the Songliao Basin and its periphery. The measured thermal conductivity ranges from 0.58 to 3.94W/(m·K), with an average value of 1.96 W/(m·K). Heat generation rates vary between 0.31 and 4.98μW/m³, averaging 1.72μW/m³. A comprehensive thermal conductivity and heat generation column for the Songliao Basin was established by integrating current testing data with previous records. Based on data from over 3000 oil test temperatures collected in this study and previous temperature data compilations, the temperature distribution characteristics of the Songliao Basin were clarified. The overall geothermal gradient averages 40-50℃/km, with terrestrial heat flow ranging between 50-100 mW/m² and exceeding 80 mW/m² in most areas. The heat generation contribution from different lithologies in each stratum was calculated based on the heat generation rate. The sedimentary layer's heat generation contribution is primarily between 5-10 mW/m². The mantle heat flow surpasses crustal heat flow, constituting approximately 60% of the total heat flow. A partial melt in the crust of the Songliao Basin contributes about 10% to heat generation contribution, with a notable impact on mantle heat flow. The Songliao Basin underwent testing for apatite fission track and (U-Th)/He age, coupled with a Meso-Cenozoic thermal history simulation. The outcomes reveal a substantial cooling trend in the basin starting at the end of the Cretaceous period, persisting to the present day. This analysis contributes to a more comprehensive understanding of the formation history of the current geotemperature field within the study area. The study analyzes the influence of the deep thermal background on high-temperature geothermal accumulation by scrutinizing the distribution characteristics of thermal lithospheric thickness, the Moho surface, and the Curie isotherm, along with exploring the correlations among these factors. A comprehensive analysis, considering reservoirs, channels, caps, and fluid origin, establishes the formation conditions of high-temperature geothermal resources. Factors controlling and high-temperature geothermal accumulation are clearly defined, culminating in the establishment of a high-temperature geothermal accumulation model for the Songliao Basin.

How to cite: Tang, B., Qiu, N., and Zhu, C.: Formation mechanism of high-temperature geothermal resources in the Songliao Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21159, https://doi.org/10.5194/egusphere-egu24-21159, 2024.

Abstract :

Geothermal energy is becoming increasingly important in the transition to low-carbon and sustainable energy sources. The present article explores the Life Cycle Assessment (LCA) and the long-term sustainability of geothermal energy through the analysis of this sector’s impact from resource extraction to end-of-life in N-Hungary.

This study undertakes a thorough investigation with the goal of synthesizing current knowledge, identifying the geothermal system in the vicinity of Veresegyház, N-Hungary and offering a coherent understanding of geothermal energy as well as the environmental sustainability, since that this town is a notable example of a smart and conscious local community that recognized and harnessed its geothermal energy potential. Veresegyház started using geothermal energy in 1993, it has become one of the largest urban geothermal heating systems in Hungary, showcasing ongoing advancements in geothermal energy utilization. The total installed thermal capacity of the system is nearly 13 MW. The geothermal energy provides about 74 TJ annually, what leads to saving almost 2.2 million m³ natural gas per year. The geothermal system is used for heating and domestic hot water purposes; besides it has a total installed thermal capacity of nearly 13 MW and an extensive geothermal pipeline stretching 18 km making it one of Hungary's most comprehensive geothermal systems.

The aim in this article is to provide an insight into the geothermal technologies, exploring the appropriate methodology of life cycle assessment (LCA), and compare the results with previous studies.

Key Words:

Geothermal Energy, Renewable Energy, Life Cycle Assessment (LCA), Environmental Impact, Sustainability, Energy Transition, Case Studies, Policy, Carbon Footprint.

How to cite: Khedhri, R. and Hámor Vidó, M.: “Life Cycle Assessment of Geothermal Energy: preliminary overview of the Veresegyház geothermal system”, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18270, https://doi.org/10.5194/egusphere-egu24-18270, 2024.