ERE2.6 | Geothermal systems: Exploration, Exploitation and Monitoring of Geothermal Resources
EDI
Geothermal systems: Exploration, Exploitation and Monitoring of Geothermal Resources
Convener: Domenico Montanari | Co-conveners: Matteo Lupi, Evgeniia MartuganovaECSECS
Orals
| Thu, 18 Apr, 08:30–12:05 (CEST), 14:00–15:15 (CEST)
 
Room 0.94/95
Posters on site
| Attendance Fri, 19 Apr, 10:45–12:30 (CEST) | Display Fri, 19 Apr, 08:30–12:30
 
Hall X4
Orals |
Thu, 08:30
Fri, 10:45
Clean-Energy Transition is a central concept to energy and climate policies, and in this context the need for geothermal resources utilization is accelerating. Geothermal energy can be extracted from different, often complex, geological settings (e.g., fractured crystalline rock, magmatic systems, or sedimentary basins). Current advancements also target unconventional systems (e.g., enhanced geothermal systems, super-hot, pressurized and co-produced, super-critical systems) besides conventional hydrothermal systems. Optimizing investments leads also to the development of associated resources such as lithium, rare earth elements and hydrogen.

Such a variety of conditions requires a joint effort for understanding and modelling geological systems that are specific to each resource. The ssustainable use of geothermal resources requires an advanced understanding of the properties of the entire system at every stage of geothermal field development. This includes but it is not limited to geophysical properties, thermo-/petro-physical conditions, fluid composition, structural and hydrological features, and engineering considerations. The main challenges faced are, among others, exploration of blind systems, reservoir stimulation, environmental concerns, induced seismicity, multiphase fluid and scaling processes, monitoring.
The integration of analogue field studies with real-life production data, from industrial as well as research sites, and with numerical models, is a hot topic worldwide. We aim to gather field, laboratory and numerical experts who focus their research on geothermal sites, to stimulate discussion in this multidisciplinary applied research field. We encourage contributions from experts from a broad range of disciplines such as (hydro)geologists, geochemists, (geo)physicists, surface and subsurface engineers. The aim of this session is to gather inputs focusing on the interplay between different approaches. We welcome contributions from different research areas ranging from field data collection and analysis to laboratory experiments (e.g., geophysical surveys, structural characterization, geomechanical, geochemical experiments), and from data management and organization to numerical modeling.

Orals: Thu, 18 Apr | Room 0.94/95

Chairpersons: Domenico Montanari, Matteo Lupi, Evgeniia Martuganova
08:30–08:40
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EGU24-3906
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Virtual presentation
Füsun Tut Haklıdır, Raziye Şengün Çetin, and İnci Selcen Görgülü

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.

08:40–08:50
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EGU24-9017
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On-site presentation
Diego Morata, Santiago Maza, Isabel Abad, Cristóbal Cuevas, and Gloria Arancibia

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.

08:50–09:00
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EGU24-19542
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ECS
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On-site presentation
Beatrice Giuliante, Philippe Jousset, Charlotte Krawczyk, Jacques Hinderer, Umberto Riccardi, Nolwenn Portier, Florian Forster, and Anette K. Mortensen

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.

09:00–09:10
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EGU24-5413
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ECS
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On-site presentation
Immanuel Weber and Torsten Tischner

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.

09:10–09:20
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EGU24-10911
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On-site presentation
Gloria Arancibia, Valentina Mura, Camila López-Contreras, Isa Oyarzo, John Browning, David Healy, Santiago Maza, and Diego Morata

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.

09:20–09:30
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EGU24-12301
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ECS
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On-site presentation
Alba Martín Lorenzo, Karen Copete-Murillo, Ángel Reyes, Ana Gironés, Gladys V. Melián, María Asensio-Ramos, Fátima Rodríguez, Eleazar Padrón, Germán D. Padilla, Pedro A. Hernández, and Nemesio M. Pérez

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.

09:30–09:40
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EGU24-13014
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ECS
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On-site presentation
Enhanced magma cooling during geothermal stimulation
(withdrawn)
Kyriaki Drymoni, Edgar Zorn, Janine Birnbaum, Jackie Evan Kendrick, Anthony Lamur, Társilo Girona, Falk Amelung, Joachim Gottsmann, and Yan Lavallée
09:40–09:50
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EGU24-9278
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ECS
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On-site presentation
Sasa Guo, Yue Cui, and Boning Tang

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.

09:50–10:00
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EGU24-15521
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On-site presentation
Barbara Cantucci Marini, Monia Procesi, Franco Tassi, Carlo Cardellini, Carmine Apollaro, Dmitri Rouwet, Francesca Zorzi, Giovanni Vespasiano, Emanuela Bagnato, Giancarlo Tamburello, Stefania Venturi, Daniele Cinti, and Donato Belmonte

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.

10:00–10:10
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EGU24-6049
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On-site presentation
Fiorenza Deon, Ingo Sass, Claire Bossennec, Anselm Loges, Oona Appelt, Lukas Seib, Harald Milsch, and Günter Zimmermann

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.

10:10–10:15
Coffee break
Chairpersons: Matteo Lupi, Domenico Montanari, Evgeniia Martuganova
10:45–11:05
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EGU24-7014
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solicited
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On-site presentation
Sophie Pearson-Grant, Edward Bertrand, Craig Miller, and Lucy Carson

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.

11:05–11:15
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EGU24-8152
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ECS
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On-site presentation
Emma L. Chambers, Duygu Kiyan, Riccardo Pasquali, Javier Fullea, Pat Meere, Sergei Lebedev, Chris Bean, and Brian O'Reilly

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.

11:15–11:25
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EGU24-20195
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On-site presentation
Xiaofan Wan, Chuanbo Shen, and Xiang Ge

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.

11:25–11:35
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EGU24-14595
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ECS
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On-site presentation
Lulu Lei, Sheng Jin, Hao Dong, Wenbo Wei, Gaofeng Ye, and Letian Zhang

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.

11:35–11:45
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EGU24-15055
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ECS
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On-site presentation
Leandra Weydt, Jeroen van der Vaart, and Ingo Sass

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.

11:45–11:55
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EGU24-16021
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On-site presentation
Ana Gironés, Anna Valls, Maisie Thompson, Alba Martín, Nemesio M. Pérez, Gladys V. Melián, Eleazar Padrón, Germán D. Padilla, Pedro A. Hernández, María Asensio-Ramos, and Fátima Rodríguez

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.

11:55–12:05
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EGU24-16282
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Highlight
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On-site presentation
Katharina Alms, Alicia Groeneweg, and Manfred Heinelt

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.

Lunch break
Chairpersons: Evgeniia Martuganova, Matteo Lupi, Domenico Montanari
14:00–14:10
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EGU24-19591
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ECS
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On-site presentation
Evelina Dallara, Matteo Lelli, Paolo Fulignati, and Anna Gioncada

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.

14:10–14:20
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EGU24-16639
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On-site presentation
Iwona Galeczka, Finnbogi Óskarsson, and Kiflom Gebrehiwot Mesfin

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 11th, 2016, and it was completed on January 25th, 2017. The most recent well test of RN-15/IDDP-2 was on 5th 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.

14:20–14:30
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EGU24-17431
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ECS
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On-site presentation
Dilshan Bandara, Jeroen Smit, Stefan Wohnlich, and Thomas Heinze

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.

14:30–14:40
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EGU24-17923
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ECS
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On-site presentation
Giulio Bini, Giovanni Chiodini, Tullio Ricci, Alessandra Sciarra, Stefano Caliro, Anette K. Mortensen, Marco Martini, Andrew Mitchell, Alessandro Santi, and Antonio Costa

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.

14:40–14:50
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EGU24-18004
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ECS
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On-site presentation
Christopher Brown, Isa Kolo, David Banks, and Gioia Falcone

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.

14:50–15:00
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EGU24-21159
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ECS
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On-site presentation
Boning Tang, Nansheng Qiu, and Chuanqing Zhu

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.

15:00–15:10
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EGU24-18270
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ECS
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Virtual presentation
Rim Khedhri and Mária Hámor Vidó

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.

15:10–15:15

Posters on site: Fri, 19 Apr, 10:45–12:30 | Hall X4

Display time: Fri, 19 Apr 08:30–Fri, 19 Apr 12:30
Chairpersons: Domenico Montanari, Matteo Lupi, Evgeniia Martuganova
X4.158
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EGU24-12590
Gianluca Gola, Magdala Tesauro, Antonio Gargaro, and Adele Manzella

Geothermal energy, as a renewable and green source for power generation and district heating and/or cooling, is available all year round, at all times of the day, and has great potential for development in any country. However, the exploitation of deep geothermal resources is only possible after detailed characterization of the potential reservoir. In fact, knowledge of the thermo-physical properties of the underground reservoir is crucial for generate a forecast  estimation of the geothermal reservoir thermodynamic behavior, as well as for mining risk reduction and optimization of the sound design of geothermal energy production systems.

The InGEO project (Innovation in GEOthermal resources and reserves potential assessment for the decarbonisation of power/thermal sectors) aims to develop an innovative exploration workflow integrating geophysical data and other direct and indirect information, organized to make available a sort of decision support system of geothermal projects. It consists of the reconstruction of the crustal and subcrustal structures by joint analyses and interpretations of available and acquired geological and geophysical data (e.g., those provided by mechanical and thermal rock samples laboratory analyses, seismic and gravity anomalies), taking advantage of the different sensitivity that geophysical methods have on physical rock's parameters (temperature and composition). The results will be the input for the geothermal model that will quantify the deep geothermal resource potential of the area. The designed workflow will be tested in a case study area and partially calibrated with developed (hydrothermal) available data. The methodological approach proposed by InGEO is also expected to define the potential local use of geothermal systems by Deep Closed-loop Borehole Heat Exchangers (DBHE) for power generation, district heating and/or cooling. The InGEO results will contribute to the second mission of PNRR “MISSION 2: GREEN REVOLUTION AND ECOLOGICAL TRANSITION”, by expanding the business planning of deep geothermal resource use in Italy.

The test area, chosen because it is considered particularly representative of the project topic and of potential reproducibility, includes the sector of the Northern Apennine buried structures, belonging to the Romagna and Ferrara Folds (RFF). The RFF area has been the target of previous geothermal studies highlighting relatively low geothermal gradients within the deep carbonate units (on average 14 °C/km) and more significant thermal gradients (on average 53 °C/km) in the overlying impermeable formations [1-2]. This feature in temperature distribution with depth is clear evidence for fluid thermal convection occurring in the deep-seated carbonate units of Mesozoic age, which constitutes the local geothermal reservoir.

[1] Pasquale et al., 2013. Evidence for thermal convection in the deep carbonate aquifer of the eastern sector of the Po Plain Italy. Tectonophysics, 594, 1-12.

[2] Pasquale et al., 2014. Heat flow and geothermal resources in northern Italy. Ren. Sust. Energy Rev., 36, 277-285.

How to cite: Gola, G., Tesauro, M., Gargaro, A., and Manzella, A.: InGEO: GEOthermal resources and reserves potential assessment for the decarbonisation of power/thermal sectors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12590, https://doi.org/10.5194/egusphere-egu24-12590, 2024.

X4.159
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EGU24-5315
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ECS
Daniele Maestrelli, Giacomo Corti, Marco Bonini, Derek Keir, Eugenio Trumpy, Pietro Facincani, Paola Vannucchi, Chiara Del Ventisette, Domenico Montanari, and Federico Sani

Collapsed calderas are prominent volcano-tectonic features occurring in active tectonic settings and bear intrinsic risks associated with their explosiveness. Nonetheless, they also represent key targets for geothermal fluid exploration, their structures being often the preferential pathway for geothermal fluids migration. In active tectonic settings such as continental rifts, caldera faults may be reactivated, enhancing therefore their permeability. However, specific structures may be subject to clamping, consequently reducing their secondary porosity. Discriminating if and how caldera structures may respond to tectonic stresses, represents therefore a critical question to address when calderas become the locus of potential geothermal exploration. We performed an experimental series of analogue models of caldera collapse exploring whether caldera structures may reactivate under extensional tectonic conditions. This analysis is important for evaluating which caldera fault segments may be regarded as the best potential target for fluid interception. Our experimental series shows that regional extension and fault dip can explain the reactivation of specific caldera fault segments. In particular, outer normal ring faults do reactivate under extensional conditions only in the sectors trending orthogonally to the direction of extension. Conversely, inner outward-dipping reverse faults do not reactivate, likely because of their lower dip angle, whichever their trend might be. This implies that inward-dipping normal faults trending orthogonal to direction of extension likely increase their permeability, thus becoming a favourable locus for geothermal fluid migration and therefore a preferable target for exploration. Conversely, our models show that sectors of inward-dipping normal caldera faults trending parallel to the direction of extension may experience clamping, and so reducing their secondary permeability. Therefore, our setup, with due approximations and limitations, represents a useful predictive tool for identifying potential target structures for geothermal exploration at caldera sites. The model setup can also provide insights into similar caldera systems developing in other geological settings (e.g., compressional).

How to cite: Maestrelli, D., Corti, G., Bonini, M., Keir, D., Trumpy, E., Facincani, P., Vannucchi, P., Del Ventisette, C., Montanari, D., and Sani, F.: Reactivation of caldera structures in active extensional settings: implication for geothermal exploration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5315, https://doi.org/10.5194/egusphere-egu24-5315, 2024.

X4.160
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EGU24-22111
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ECS
Genevieve Savard, Iván Cabrera-Pérez, Julien Sfalcin, and Matteo Lupi

As part of the Net Zero climate strategies of the European Union and Switzerland, deep geothermal power production is given an important role to play as a baseload energy resource. In Switzerland, the Haute Sorne project of Geo-Energie Suisse is the first EGS geothermal project to take place since the unsuccessful project of Basel terminated in 2010. The Canton of Jura, where Haute Sorne is located, gave the green light to Geo-Energie Suisse in January 2022. To minimize the risk of damaging induced seismicity as in 2017 during the Pohang EGS project, innovative state-of-the-art exploration and monitoring methods at Haute Sorne are being implemented to reduce subsurface uncertainty and de-risk the project as much as possible.

In this context, the University of Geneva is deploying a seismic network of 700 nodal sensors in February 2024 in a radius of 12 km around the planned Haute Sorne EGS site. The sensors will record continuous 3-component seismic velocity data passively over 30 days. Using ambient noise tomography techniques, this study aims to image at up to 5 kilometres depth regional-scale structures relevant to seismic hazard assessment and to understand the local seismo-tectonic context. Particular interest is given to basement-related structures including a nearby presumed Permo-Carboniferous trough. By examining anomalies in shear-wave velocity, radial anisotropy and/or attenuation, we aim to elucidate the presence of deep faults and/or deep fluid reservoirs. In this presentation, we will report the outcomes of the nodal deployment campaign, the quality of the data collected, preliminary ambient noise observations and the methods to be applied. Passive seismic campaigns with temporary nodal networks have great potential for geothermal exploration due to their low cost, easier permitting process, and ability to image basement-related structures with appropriately designed networks.

How to cite: Savard, G., Cabrera-Pérez, I., Sfalcin, J., and Lupi, M.: Passive seismic exploration with a dense network of 700 sensors in the Canton of Jura, Switzerland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22111, https://doi.org/10.5194/egusphere-egu24-22111, 2024.

X4.161
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EGU24-11688
Domenico Montanari, Riccardo Lanari, Marco Marco, Samuele Papeschi, Chiara Del Ventisette, and Matteo Lupi

Geomorphological techniques are used worldwide to explore how the topography responds to surface, crustal and mantle processes. This is the case for the recent developed river dynamic model inversion, that promises to return time vs uplift rate histories required to achieve the modern fluvial configurations. In the framework of the ‘Migrate Project’, a multidisciplinary project combining geology, seismology and machine learning financially supported by the SNSF, we test a novel method of rivers inversion to constrain the surface vertical movements caused by the emplacement of middle-shallow crustal magmatic pluton. We selected, as case study, the Larderello-Travale Geothermal System (LTGS), in the northern Italian Apennines, where multiple magmatic bodies intruded since the late Pliocene causing a large-wavelength surface uplift of at least 600 meters. However, since none of the LTGS plutons reach the surface, their spatial distribution is only constrained by exploration wells or geophysical investigations. Our work aims to: (1) quantify the surface response to pluton emplacement and (2) identify intrusions not yet documented in the area.

We modelled 31 river basins draining the LTGS and surrounding regions. For all catchments, the available ages of plutons constrained by wells, spatially correlate with the local peaks of increasing uplift rates (> 0.2 mm/y). We document a diffuse regional uplift during middle/late Pliocene, likely a consequence of the first magmatic pluton emplacement, followed by a continuous uplift throughout Quaternary times. However, during this time interval, the uplift style changed to confined pulses, which we interpret as locally emplaced magmatic batches. In addition, uplift rates decreased systematically from 0.6 Ma to present, which suggests a potential reduction on the topographic response to magma emplacement, even if the thermal anomaly is still quite evident. This work confirms that plutons provide a topographic swell, and we suggest that our approach could be used to locate undocumented plutons, leading to new potential strategies for geothermal exploration.

How to cite: Montanari, D., Lanari, R., Marco, M., Papeschi, S., Del Ventisette, C., and Lupi, M.: Morphological analysis and river inversion as a proxy to constraint upper crustal magmatic pluton emplacements: evidence from the Larderello-Travale Geothermal System, northern Apennines. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11688, https://doi.org/10.5194/egusphere-egu24-11688, 2024.

X4.162
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EGU24-6759
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ECS
Samuele Papeschi, Amy Moser, Marco Bonini, Chiara Del Ventisette, Riccardo Lanari, Matteo Lupi, and Domenico Montanari

Plutons in the Northern Apennines are generally thought to have been emplaced under low-angle normal faults (LANFs). However, the limited knowledge of their emplacement depth hinders a full understanding of their exhumation history and the tectonic setting in which they emplaced remains heavily debated. Indeed, granites in the Tuscan Archipelago are loosely constrained to P < 2 kbar, roughly corresponding to a maximum emplacement depth of 7-8 km. When considering that faults interpreted as LANFs in the area only show limited total displacements of a few km, the lack of constraints on the minimum depth of emplacement make it impossible to reconstruct the exhumation history of plutons in the area based on geochronology and low-temperature thermochronology only. Here we present the first precise constraints on the depth of magma emplacement on the Island of Elba, in the hinterland zone of the Northern Apennines. We investigated a spotted schist from the Terranera area of Eastern Elba, located in the footwall of the Zuccale Fault. The schist displays the garnet + cordierite metamorphic assemblage, which is very uncommon in the low-pressure Elban aureoles. We performed a detailed microstructural and petrographic study coupled with the analysis of mineral and bulk-rock chemistry through the Electron Microprobe and X-ray Fluorescence.

We modelled the sample with the phase equilibrium modelling approach using the PerpleX software, constraining the co-stability of garnet and cordierite to the narrow P interval of 0.3 – 1.2 kbar, corresponding to 1.1 – 4.4 km depth. Considering the limited horizontal throw of the Zuccale Fault, of just ~6 km and its current subhorizontal attitude, it is unrealistic that this fault contributed significantly to the exhumation of igneous rocks in eastern Elba. Rather, the estimated pressure is consistent with the thickness of the Northern Apennines orogenic nappe pile exposed on the island. Nevertheless, we acknowledge the need to obtain precise P constraints also from the Zuccale Fault footwall and we discuss P constraints derived from metamorphic assemblages therein.

We also provide the first U/Pb monazite ages of the young aureole which constrain peak metamorphic temperature to 6.7 ± 0.2 Ma. Considering the published radiometric constraints from the area, we suggest that Eastern Elba experienced a long-lived pluton-related thermal anomaly that persisted for ~0.8 – 1.2 Ma before cooling down to ‘normal’ upper crustal conditions, similar to the nearby, younger Larderello geothermal field.

This work was carried out as part of the MIGRATE project, funded by the SNFS.

How to cite: Papeschi, S., Moser, A., Bonini, M., Del Ventisette, C., Lanari, R., Lupi, M., and Montanari, D.: Depth and time constraints on monzogranite emplacement and cooling in the Northern Tyrrhenian Sea: implications for the exhumation history of the Zuccale Fault (Island of Elba, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6759, https://doi.org/10.5194/egusphere-egu24-6759, 2024.

X4.163
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EGU24-5595
Michael Kühn, Paul Viskovic, and Thomas Kempka

Waiwera is a small coastal village located on New Zealand's North Island. The geothermal reservoir below the town consists of compacted and cemented sandstones and siltstones of the Waitemata Group [1]. These are some 400-m thick and have been folded, faulted and fractured by tectonic processes throughout the entire depth. The source of the hot water is not well understood because the deeper structure of the field has mainly been inferred from the spatial distribution of thermal water from producing bores. An inferred fault zone at the base of the reservoir is thought to be the source of the upwelling thermal water.

The most recent model of Waiwera integrates the depositional environment, mineralogical composition and geological structures [2]. Numerical simulations indicated that further model revisions are required with support by additional field campaigns to increase the knowledge of the complex reservoir geology [3].

In this study, gravity data from 77 new stations were acquired around the greater Waiwera area, modelled and interpreted. Two 2.5D gravity models show a 180-m high, NNW-trending step that may represent either steep topography or a fault downthrow to the east in the basement. The position and size of this step are well constrained, but the feature is too deep to confidently predict the dip, and hence is modelled as being almost vertical. This feature may provide a focus for hot water to rise upwards into the Waiwera geothermal system [4].

Further, radiocarbon analysis of three groundwater samples show that age of the geothermal water at Waiwera is >20,000 years with <0.005% of hydrogeologically young water. Geochemical analyses show possible saltwater intrusion near the coast and the highest observed concentrations of geothermal chemical components near the main production well of the thermal resort, close to the modelled fault location.

New models will be implemented with the updated information to investigate a revised conceptual model. We will test if the assumption of hot water accumulating in sedimentary basins away from Waiwera and travelling laterally up-dip near the base of the Waitemata Group sediments and then rising vertically under the Waiwera township is a feasible hypothesis to better represent the system.

 

[1] Kühn, M., Stöfen, H. (2005): A reactive flow model of the geothermal reservoir Waiwera, New Zealand. - Hydrogeology Journal, 13, 4, 606-626. https://doi.org/10.1007/s10040-004-0377-6

[2] Kühn, M., Präg, M., Becker, I., Hilgers, C., Grafe, A., Kempka, T. (2022): Geographic Information System (GIS) as a basis for the next generation of hydrogeological models to manage the geothermal area Waiwera (New Zealand). - Advances in Geosciences, 58, 31-39. https://doi.org/10.5194/adgeo-58-31-2022

[3] Kempka, T., Kühn, M. (2023): Numerical simulation of spatial temperature and salinity distribution in the Waiwera geothermal reservoir, New Zealand. - Grundwasser, 28, 243-254. https://doi.org/10.1007/s00767-023-00551-8

[4] Präg, M., Becker, I., Hilgers, C., Walter, T. R., Kühn, M. (2020): Thermal UAS survey of reactivated hot spring activity in Waiwera, New Zealand. - Advances in Geosciences, 54, 165-171. https://doi.org/10.5194/adgeo-54-165-2020

How to cite: Kühn, M., Viskovic, P., and Kempka, T.: New data for a model update of the Waiwera geothermal reservoir in New Zealand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5595, https://doi.org/10.5194/egusphere-egu24-5595, 2024.

X4.164
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EGU24-9927
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ECS
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solicited
Ábel Markó, Tamara Tóthi, Imre Szilágyi, and Judit Mádl-Szőnyi

In our research, we develop a novel methodology to evaluate the geological uncertainties of geothermal exploration in order to quantify them. The outcomes can be used as inputs when deciding on new geothermal investments. Adapted from the hydrocarbon industry probability of success is evaluated by estimating potential geological risk factors which can hinder geothermal production and reinjection, following the risk assessment scheme of petroleum play analysis.

As a case study in a clastic geological environment, we test the methodology on the Zala Basin, a sedimentary subbasin of the Pannonian Basin, Hungary. Here, the Neogene (so-called Pannonian) sediments form one of the principal thermal water-reservoirs. Although the preliminary geothermal potential of the Zala region (SW Hungary) is assessed to be good, there is a need for more thorough analysis before starting new developments. As an example, heterogeneity of the deltaic and fluvial deposits poses geological risk. In our case study, we consider the risk of insufficient temperature, the absence of the appropriate aquifer formations, the bad quality of the aquifer i.e., the unfavourable distribution of the high permeable sandstone bodies, the insufficient permeability and flow rate as well as the potential risk of unsuccessful reinjection. This is done by combining and evaluating datasets from well data (lithology, well logs, well tests) and 3D seismic measurements. The goal of the assessment is to decide whether a future geothermal system can provide sufficient capacity, in the current case, for industrial or agricultural heat utilisation.

The first author was supported, and the research was financed through the KDP-2021 Cooperative Doctoral Programme of the Ministry of Innovation and Technology (Hungary) from the source of the National Research, Development and Innovation Fund, grant number: KDP_2021_ELTE_C1789026. The study was funded by the National Multidisciplinary Laboratory for Climate Change, RRF-2.3.1-21- 2022-00014 project.

How to cite: Markó, Á., Tóthi, T., Szilágyi, I., and Mádl-Szőnyi, J.: Geological risk analysis of geothermal developments in a sedimentary basin, Hungary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9927, https://doi.org/10.5194/egusphere-egu24-9927, 2024.

X4.165
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EGU24-17038
Maria Giulia Di Giuseppe, Stefano Carlino, Claudio De Paola, Giuseppe Ferrara, Giovanni Florio, Roberto Isaia, Fabio Pagliara, Tommaso Pivetta, Umberto Riccardi, Lorenzo Ricciardi, Monica Sposato, Antonio Troiano, and Luigi Zampa

Pantelleria island in Southern Italy represents an attractive target area for geothermal energy exploitation. The island is characterised by a high-temperature geothermal system (>150°C/km, as detected from deep borehole measurements), hot fluids, and CO2 diffuse degassing. Pantelleria has already been the subject of several studies to assess its geothermal potential. To further increase the knowledge about geometry and the physical properties of the main structures of the geothermal system, new magnetotelluric (MT) and gravity surveys have been carried out. The MT modelling relies on the inversion of data collected in 78 independent soundings covering the whole island. Through this survey, a 3D model of the electrical resistivity has been retrieved, highlighting the structures of Pantelleria down to a depth of 2.5 km b.g.l. A new gravity survey of about 120 stations allowed us to obtain new and more detailed Free Air and Bouguer gravity maps, with a spatial resolution of about 600 m. 

How to cite: Di Giuseppe, M. G., Carlino, S., De Paola, C., Ferrara, G., Florio, G., Isaia, R., Pagliara, F., Pivetta, T., Riccardi, U., Ricciardi, L., Sposato, M., Troiano, A., and Zampa, L.: Magnetotelluric and Gravity surveys of Pantelleria Island (Southern Italy) for geothermal exploration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17038, https://doi.org/10.5194/egusphere-egu24-17038, 2024.

X4.166
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EGU24-19205
Giacomo Corti, Marxo Benvenuti, Derek Keir, and Federico Sani

Although systems of extension-orthogonal normal faults are the typical expression of continental rifting, structures oblique or even sub-parallel to the plate motion vector may at places develop. These transversal structures, which may be related to reactivation of pre-existing structures, have been suggested to have a control on rift-related volcanism and caldera systems (for instance controlling their extension-parallel elongation) and on the circulation of fluids in geothermal fields associated to these volcanic features. Here we present data from the central sector of the Main Ethiopian Rift showing the existence of a major NW-SE trending system, which likely resulted from the linkage of major segments of the Main Ethiopian Rift exploiting pre-existing structures. This transversal structure, characterised by both a normal and right lateral slip component, influenced the morphology, hydrography, seismicity and volcanism in the area. Specifically, this NW-SE structure, and the interaction with the NE-SW faults delimiting the rift, controlled the location and alignment of silicic volcanism in the Bora-Bericha and Tulu Moye systems. Seismicity analysis indicates that this transverse structure is still active, reaching at least mid-crustal depths, and indicates that this structure is involved in the fluid circulation at upper crustal levels in the associated geothermal system. Therefore, transverse structures may have important influence on rift evolution and architecture and on the pathways of magma and on the flow pattern of crustal fluids, with important implications for geothermal activity related to continental rifting, as suggested for other important geothermal fields in the Main Ethiopian Rift.

How to cite: Corti, G., Benvenuti, M., Keir, D., and Sani, F.: Transversal structures in the Main Ethiopian Rift and implications for rifting, volcanism and geothermal systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19205, https://doi.org/10.5194/egusphere-egu24-19205, 2024.

X4.167
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EGU24-5687
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ECS
Tamara Tóthi, Ábel Markó, Imre Szilágyi, and Judit Mádl-Szőnyi

The Buda Thermal Karst system is one of the best-known hypogenic karst areas. In addition, it is located below the city of Budapest. The groundwater of the confined and unconfined carbonate system is characterised by complex gravity and buoyancy-driven flow. It is associated with a complex geological setup characterised by significant heterogeneity in permeability distribution, resulting in exploration uncertainty. The utilisation of thermal water in the area goes back to the Roman Empire through springs, but from the 19th century, wells have been deepened. In Budapest, outstanding thermal wells and projects have been developed. However, several unsuccessful attempts also occurred in SE Budapest due to geological uncertainty, lack of knowledge and proper pre-analysis.

Motivated by the green transition and the energy crisis, the geothermal utilisation of the thermal water in the area has become the focus of interest nowadays. The geothermal risk assessment can be a helpful tool to quantify the uncertainties of the exploration of such a complex system. In this research, we develop a novel methodology to analyse and quantify the geological risk of geothermal developments, focusing on the deep and thick carbonate reservoir. The new approach is adapted from the petroleum industry and follows the risk assessment scheme of petroleum play analysis.

The methodology was tested in a local study area in northeast Budapest, where the required geothermal capacity for heating was previously determined. Here, the Neogene siliciclastic sediments cover the Triassic carbonates, which serve as thermal water reservoirs. To estimate whether a future geothermal system can provide sufficient capacity, in this study, the probability of success is assessed by evaluating potential geological risk factors which can hinder geothermal production and reinjection. This is done by combining and evaluating datasets on aquifer and water quality, temperature and flow conditions using lithological data, geophysical logs (cavities), temperature-elevation, and pressure-elevation profiles. The outcomes of the research help in decision-making while preparing new geothermal developments.

This research was supported and financed through the KDP-2021 Cooperative Doctoral Programme of the Ministry of Culture and Innovation of Hungary from the source of the National Research, Development and Innovation Fund, grant number: KDP 2021 _ELTE_C 1789026. The research is funded by the National Multidisciplinary Laboratory for Climate Change, RRF-2.3.1-21-2022-00014 project.

How to cite: Tóthi, T., Markó, Á., Szilágyi, I., and Mádl-Szőnyi, J.: Geological risk analysis of geothermal developments in the Buda thermal karst area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5687, https://doi.org/10.5194/egusphere-egu24-5687, 2024.

X4.168
|
EGU24-3862
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ECS
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Hong-Mao Huang, Hsin-Hua Huang, Yung-en Yu, Gong-Ruei Ho, Min-Hung Shih, Ya-Chuan Lai, Po-Li Su, Hung-Yu Yen, Tsung-Chih Chi, Cheng-Horng Lin, Jian-Cheng Lee, Yue-Gau Chen, and Sun-Lin Chung

Geothermal energy serves as one of sustainable and low-emission energy sources with the potential to mitigate climate change and enhance energy security. It offers a viable substitute for conventional fossil fuels or electrical energy. The Hongchailin area in Ilan, Taiwan has been considered as a potential geothermal energy field in recent years. To investigate possible geothermal sources in Hongchailin, a dense seismic array comprising 186 geophones is deployed over a 5 × 4 km area covering the probable geothermal field between August 2022 and January 2023. A vibroseis experiment was operated along multiple lines across the array with 12-second sweep-frequency signals from 6 to 96 Hz. To retrieve clear vibroseis-generated P-wave arrivals, we first remove the sweep signals from the raw waveforms by the cross-correlation method, and stack the processed waveforms from successive co-site shots with the Phase-Weighted Stacking (PWS) method to improve the signal-to-noise ratio. We use the Recursive-STA/LTA method for P-wave arrival picking. Visual inspection and additional criteria are made for confirming and refining the accuracy of P-arrivals. Lastly, a total of 41,095 P-arrivals are collected and used for seismic tomographic inversion. The velocity model shows several velocity anomaly zones in good spatial correlation with the resistivity model, although the resolvable depth of the model is limited to ~1 km. It demonstrates the active-source seismic tomography as a valuable geothermal exploration tool. Further, we employ unsupervised learning methods to classify and explore the resistivity-velocity relationships in each cluster. The preliminary results indicate a positive linear correlation for some regions but negative for some others, implying different materials such as rock composition or fluid content. These findings provide valuable insights for comprehensive understanding of geothermal resources in the Hongchailin area.

How to cite: Huang, H.-M., Huang, H.-H., Yu, Y., Ho, G.-R., Shih, M.-H., Lai, Y.-C., Su, P.-L., Yen, H.-Y., Chi, T.-C., Lin, C.-H., Lee, J.-C., Chen, Y.-G., and Chung, S.-L.: Integrated geothermal exploration of Hongchailin geothermal field in Taiwan using seismic velocity and resistivity tomography with unsupervised learning analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3862, https://doi.org/10.5194/egusphere-egu24-3862, 2024.

X4.169
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EGU24-7029
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Shao-Yi Huang, Wen-Shan Chen, Hsien-Hsiang Hsieh, Wei-Hao Hsu, Hao Kuo-Chen, Ching-Wee Lin, Li-Hung Lin, Lun-Tao Tong, and Pei-Ling Wang

Taiwan, one of the most active orogens in the world, sits on the convergent plate boundary between the Luzon Arc of the Philippine Sea Plate and the continental margin of the Eurasian Plate. The Philippine Sea Plate continuously moves northwest and leads to the intense processes of mountain building. Consequently, the island presents a variety of tough landforms and bears high heat flows with potential for geothermal energy. The Single Service Window for Taiwan Geothermal Power estimated total geothermal potential around the island of Taiwan to be about 33.64 GW. The study area, Paolai Hot Spring, is known as one of the potential geothermal sites in Taiwan. The village situates upon the Laonung River, which drains across the low degree metamorphic strata, and is bounded by the Chaozhou Fault to the west. The Chaozhou Fault is an east-dipping thrust fault that brought up the low degree metamorphic argillite-to-slate strata over the sedimentary formations. To the east of the Chaozhou Fault, some researchers also suggested the occurrence of the Meilunshan Fault as orientation of strata and foliation appear to be different across the suspected fault. However, fault displacement is not evidenced in the field and the extent of the fault is still ambiguous. In this study, we conducted extensive geological, geophysical (including Magneto-Telluric, seismic, and gravity surveys), and geochemical surveys in this region to discuss the geothermal features across the Chaozhou Fault and the Meilungshan Fault, in terms of fluid, heat, fractures and the reservoir.

Two hydrological circulation models are justified here: 1) the single fault (the Chaozhou Fault solely) model and 2) the dual fault model. In the single fault model, the Chaozhou Fault serves as the controlling boundary with groundwater replenished from the eastern Backbone Range area. The deeply circulated fluids are heated and circulating along the highly ruptured, permeable zone within the Chaozhou Fault system. In the dual fault model, the Chaozhou and Meilunshan Faults divide the hydrological circulation into two systems. To the east of the Meilunshan Fault, groundwater is replenished from the Backbone Range area, circulating downward, heated, and migrates to the surface along the open fissures on the hanging wall of the Meilunshan Fault. To the west of the Meilunshan Fault, the circulation would be restricted by the two faults. Our field results concur occurrence of the Meilunshan Fault while the geophysical and geochemical data conformably suggest distinct characteristics of water and migration of fluids across the fault. Overall, our data show complex characteristics of multiple domains bounded by the two faults and suggest that the dual-fault model is more appropriate for further evaluations of geothermal potential. In addition, fractures are identified on the hanging wall of the Meilungshan Fault, which may serve as the near surface conduits of fluids. These areas hence have potential for shallow geothermal energy development because they both show evidence of deep reservoirs and shallow fractures. Test drilling and further investigation towards the complex structures in this region should be thoroughly considered in the future.

How to cite: Huang, S.-Y., Chen, W.-S., Hsieh, H.-H., Hsu, W.-H., Kuo-Chen, H., Lin, C.-W., Lin, L.-H., Tong, L.-T., and Wang, P.-L.: Geothermal explorations of Paolai, Taiwan: integrated results from geological, geophysical, and geochemical surveys, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7029, https://doi.org/10.5194/egusphere-egu24-7029, 2024.

X4.170
|
EGU24-8494
|
ECS
María C. Romero-Toribio, Fátima Martín Hernández, Juanjo Ledo, Pilar Queralt Capdevila, Perla Piña-Varas, David Martínez van Dorth, Vicente Carlos Ruíz Martínez, Javier Pavón-Carrasco, Luca D'Auria, Nemesio Pérez, Javier Fullea, Ana Negredo, and María Luisa Osete

The energy supply of the Canary Islands currently depends on more than 95% of fossil fuel sources, with geothermal research constituting a strategic action. Geophysical monitoring is essential to understand subsurface processes and properties to significantly enhance the potential of geothermal energy development in La Palma. In the 90s and early 2000s, several geophysical surveys were conducted in the island, but data for each physical property were modelled separately. However, regional anomalies such as gravimetric and magnetic offer complementary information about target structures and therefore, can be advantageously modelled together to obtain more constrained and thus more reliable models. An intuitive and easily comprehensive 3D model is conceived to study La Palma thermal lithosphere.

Magnetic anomaly data are retrieved from the aeromagnetic flight carried out by the Instituto Geográfico Nacional (IGN) in 1993 (Socías & Mezcua, 1996). Bouguer anomaly data for this study are composed of those observed in 2005 and 2021, published in Montesino et al. (2023), and those acquired by the IGN levelling network in early 2000s. We processed the data using ZondGM3D modelling software.

As a part of our results, we aim to compare the 3D density and magnetization distribution models of La Palma after individual and joint data inversions. In addition, we will discuss and compare our results with Di Paolo et al. (2020) geothermal system revealed using magnetotellurics and the electrical resistivity model from Piña-Varas et al. (2023) volcanic monitoring, including other previous gravity and magnetic anomaly models from literature.

This study is part of the GEOTHERPAL project in which several Spanish institutions aim to perform a multidisciplinary and multiscale geophysical and geochemical imaging of La Palma Island geothermal system, essential to estimate its energy potential. More details are found at the web site of the project: http://pc213fis.fis.ucm.es/GEOTHERPAL/index.html

How to cite: Romero-Toribio, M. C., Martín Hernández, F., Ledo, J., Queralt Capdevila, P., Piña-Varas, P., Martínez van Dorth, D., Ruíz Martínez, V. C., Pavón-Carrasco, J., D'Auria, L., Pérez, N., Fullea, J., Negredo, A., and Osete, M. L.: Gravimetric and magnetic 3D joint modelling of La Palma, Canary Islands, for geothermal resources exploration., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8494, https://doi.org/10.5194/egusphere-egu24-8494, 2024.

X4.171
|
EGU24-8140
Finnbogi Óskarsson and Egbert Jolie

The greater Hengill volcanic complex in SW Iceland is located on a triple junction between the rift zone of the Reykjanes peninsula, the Western rift zone of Iceland and the South Iceland seismic zone. It is divided into three volcanic systems; Hengill, Hrómundartindur and Grændalur, each of which has associated fissure swarms. The Hengill volcanic complex is host to several geothermal areas that are spread over most of its extent, with geothermal surface manifestations generally connected to the tectonic features.

Three of the geothermal systems within the youngest volcanic system (that of Mt. Hengill) have been exploited by Reykjavík Energy which runs two geothermal power plants: Hellisheiði and Nesjavellir. The power plants produce a total of 423 MWe which is sold on the national grid and 500 MWth in the form of heated groundwater for direct use in the capital area.

We report samples of steam, gas and condensate collected from 12 fumaroles in 11 geothermal subfields defined within the Mt. Hengill fissure swarm (Nesjavellir, Nesjalaugagil, Köldulaugagil, Hagavíkurlaugar, Fremstidalur, Miðdalur, Innstidalur, Sleggjubeinsdalur, Skarðsmýrarfjall, Skíðaskáli and Hverahlíð) in October 2019. The samples were analysed for concentrations of all major gases (CO2, H2S, H2, CH4, N2, O2), stable noble gases (He, Ne, Ar, Kr, Xe) as well as the 3He/4He isotopic ratio and the stable isotope ratios of carbon (δ13CCO2), hydrogen (δD) and oxygen (δ18O). This study is relevant for the chemical characterization of the key upflow zones in the volcano-tectonic system as well as the identification of promising target areas for the installation of advanced gas monitoring systems. Monitoring data can contribute to an improved understanding of processes in the subsurface related to volcanic and seismic activity, but also to geothermal reservoir operations.

The steam has generally rather low gas concentrations, with a total gas content of less than 500 mmol/kg steam for all samples except the few that had lost steam to condensation before sampling. All samples have CO2 as the most abundant gas followed H2S and H2. Gas geothermometry suggests temperatures ranging from about 250°C to more than 320°C. The stable water isotope values of the most powerful fumaroles are in good agreement with those obtained for well fluids, but the isotope values for steam from weaker fumaroles show signs of subsurface condensation. Carbon isotopes suggest that CO2 has a magmatic origin, as is most common for Icelandic high-temperature geothermal areas. Helium isotopes show clear mantle signatures with 3He/4He as high as 16 Ra but mixing with atmosphere is also observed.

How to cite: Óskarsson, F. and Jolie, E.: Chemical and isotopic composition of steam from fumaroles in Hengill, SW Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8140, https://doi.org/10.5194/egusphere-egu24-8140, 2024.

X4.172
|
EGU24-11626
Xavier Bolós, Nicole Lautze, Mario Boijseauneau, and Mattox Telwar

The Hawaiian Islands, characterized by volcanic activity and complex hydrogeological systems, encounter energy challenges due to reliance on imported fossil fuels. Therefore, exploring geothermal sources is crucial for sustainable development, given the islands' isolation. Simultaneously, understanding freshwater reservoirs is vital for sustainable water resource management. This multidisciplinary study on Lāna’i Island integrates geophysical, groundwater, and mineralogical data, unveiling insights into concealed deep hydrothermal activity and its heat source. Correlations observed in newly acquired self-potential (SP) data combined with earlier gravity and magnetotellurics (MT) data reveal the presence of a hydrothermal upflow, perhaps originating from deep magma reservoirs beneath the Pālāwai caldera. The concealed hydrothermal system emerges as a potential geothermal resource at >2 km depth, requiring further deep drilling research to confirm its presence. In addition, XRD analysis reveals varying degrees of hydrothermal alteration, indicating high temperatures during fluid-rock interactions. The alignment of surface alteration with current upflow zones suggests an active hydrothermal system persists in the caldera faults since the shield-building stage, which causes warm brackish water within the Pālāwai basin. This prompts a discussion about the possible presence of a geothermal resource. This subject has been under investigation for the past seven years as part of the Hawaii Play Fairway project. The impact of hydrothermal activity appears limited to the Pālāwai caldera and the Canyon zone, contrasting with the Munro Trail ridge area, which serves as an independent freshwater source with impounded aquifers. Understanding this convergence of geothermal investigation and freshwater reservoir analysis holds significant importance for fostering sustainability in the Hawaiian archipelago.

How to cite: Bolós, X., Lautze, N., Boijseauneau, M., and Telwar, M.: Uncovering Lāna’i's hidden heat: geophysical insights on the subsurface hydrothermal activity of this Hawaiian island , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11626, https://doi.org/10.5194/egusphere-egu24-11626, 2024.

X4.173
|
EGU24-12047
Gladys V. Melián, Matteo Furlan, Malte Seefeld, Alba Martin-Lorenzo, Ana Gironés, Nemesio M. Pérez, Fátima Rodríguez, María Asensio-Ramos, Eleazar Padrón, Pedro A. Hernández, Germán D. Padilla, Sttefany Cartaya, and Mónica Arencibia

During geothermal exploration, the geochemical methods are extensively used and play a major role in both exploration and exploitation phases. Discovery of new geothermal systems at those areas where the resources are either hidden or lie at great depths, the geochemical methods for geothermal exploration must include soil gas surveys, based on the detection of anomalously high concentrations of some hydrothermal gases in the soil atmosphere. We report herein the results of an intensive soil gas study, focused on non-reactive and/or highly mobile gases such as helium (He) and hydrogen (H2), in Cumbre Vieja volcano, the volcanically ac tive part of La Palma island (Canary Islands, Spain). He has unique characteristics as a geochemical tracer: it is chemically inert and radioactively stable, non-biogenic, highly mobile and relatively insoluble in water. H2 is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas.

A detailed geochemical survey was carried out in an area of 25 km2 at the western side of La Palma. A total of 766 sites were sampled at 40 cm depth using a metallic probe with 60 cc hypodermic syringes and stored in 10 cc glass vials for later laboratory analyses. Spatial distribution maps of diffuse He and H2 emission were constructed to study the presence of enhanced vertical permeability areas related to high temperature hydrothermal activity at depth. As a result, the main He emission anomalies show different size well-defined concentric-shape structures, distributed along a west to east main direction. On the other hand, H2 highest fluxes are slightly more dispersed in different areas, although some of the main ones are coincident with the distribution of the well-known anomalous volcanic CO2 active diffuse degassing in Puerto Naos and La Bombilla villages. Soil He and H2 surveys have demonstrated to provide meaningful insights of areas that could be acting as preferential zones of vertical permeability that allow deep source gases migration to surface and, therefore, of potential geothermal system structures.

How to cite: Melián, G. V., Furlan, M., Seefeld, M., Martin-Lorenzo, A., Gironés, A., Pérez, N. M., Rodríguez, F., Asensio-Ramos, M., Padrón, E., Hernández, P. A., Padilla, G. D., Cartaya, S., and Arencibia, M.: Diffuse He and H2 degassing survey for geothermal exploration at La Palma, Canary Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12047, https://doi.org/10.5194/egusphere-egu24-12047, 2024.

X4.174
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EGU24-12217
Mehrdad Sardar Abadi, Michael Erb, and Inga S. Moeck

The increasing demand for renewable energy highlights a compelling necessity to exploit and use of geothermal energy in Germany. A notable research initiative in this regard is the WärmeGut project, funded by the Federal Ministry of energy and climate protection (BMWK) and aims on reconnaissance and re-evaluation of subsurface data to extend the geothermal information system of Germany, GeotIS. Specifically, Tertiary successions are hitherto underexplored because the focus of past geothermal exploration went to deeper levels below the Tertiary. One of the research goals places therefore significant emphasis on evaluating the potential of shallow to medium-depth geothermal resources of the Tertiary sandstones in the North German Basin (NGB).

In this study, we conducted a high-resolution sequence stratigraphy applied to reservoir characterization of the Tertiary sandstones in the NGB. Sequence stratigraphy holds considerable importance in geological reconstruction, significantly enhancing the precision of predictions within the domain of underground geological exploration. This aspect has received comparatively less attention, especially in the context of the Tertiary interval in the NGB. We conducted analysis of well logs from 15 sites, which included gamma ray, density, sonic, resistivity and photoelectric factor data. We investigate the temporal and spatial distribution of sandstone facies within the sequence stratigraphic framework of the Tertiary sequence in the NGB Basin. Primarily, the focus of the study revolves around the examination of four sandstone units located in the uppermost portion of the Lower Eocene, the Middle Eocene (Brüsselsand), the lower Oligocene (Neuegammer Sand), and the Upper Miocene.

The primary findings suggest that sedimentary sequences in the NGB during the Tertiary period display repetitive episodes of progradation, interspersed with periods of flooding on the depositional platform. These dynamics are notably marked by a significant increase in gamma-ray signals, which record maximum marine flooding over the basin margin. This observation underlines the cyclical nature of sedimentary processes during the Tertiary in the NGB. Each sequence is characterized by progradational and retrogradational facies, with shale predominating during the transgression phase, followed by an alternation of sand and shale. Sand and silt content gradually increases during the regression phase, with four major sandstone layers occurring at the maximum regression phases. On a spatial scale, the increasing shale content within alternating sand and shale intervals indicates the accommodation depth of the depositional system.

Additionally, we have conducted a petrophysical analysis to evaluate the quality of sandstones as a geothermal reservoir. Obtained results suggest that the porosity exceeds 5%, with variations influenced by the thickness, shale content, and depth of the respective sandstone units. However, both the thickness and petrophysical characteristics of the sandstone units demonstrate variations across different spatial scales within the NGB. The results indicate a general applicability of Tertiary sandstones for hydrothermal direct use in medium –depth level, but more detailed well log analysis is required to delineate shale successions. The study helps assess the geothermal potential of Tertiary sandstones in the NGB.

How to cite: Sardar Abadi, M., Erb, M., and Moeck, I. S.: WärmeGut: Stratigraphic Significance of Tertiary Sandstones as Potential Shallow to Medium-Depth Geothermal Reservoirs in the North German Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12217, https://doi.org/10.5194/egusphere-egu24-12217, 2024.

X4.175
|
EGU24-12849
Ortensia Amoroso, Valeria Giampaolo, Marianna Balasco, Massimo Blasone, Davide Bubbico, Paolo Capuano, Gregory De Martino, Maria Vittoria Gargiulo, Ferdinando Napolitano, Angela Perrone, Serena Panebianco, Raffaella Russo, Vincenzo Serlenga, and Tony Alfredo Stabile

This work shows the first results of activities carried out in the framework of project TOGETHER - Sustainable geothermal energy for two Southern Italy regions: geophysical resource evaluation and public awareness financed by European Union – Next Generation EU (PRIN-PNRR 2022, CUP D53D23022850001).

The deployment and sustainable use of Italy's geothermal resources could represent a key asset to increase renewable energy production and reduce greenhouse gas emissions in the years ahead. Within this context, there is an obvious need for programs to improve subsurface geothermal resource extraction while maintaining environmental sustainability.

Assessing the potential exploitation requires knowing the type of geothermal system, the likely temperature and characteristics of the reservoir rocks and fluids. We propose a novel geophysical multi-messenger approach, which provides unique and useful insights into the features and activities of examined geothermal reservoirs. These findings stem from the complementary information carried by subsoil geophysical parameters such as electrical resistivity and elastic/anelastic characteristics related to fluid presence. The proposed method will be tested in two test regions in Southern Italy that are appropriate for low to medium-enthalpy geothermal extraction: Contursi Terme and Tramutola. Contursi Terme is one of the most appreciated thermal sites in the whole Campania region. Here, 77 springs with temperatures ranging from 21°C to 30°C are present; furthermore, 72 shallower and deeper wells for the pumping of hot waters with temperatures ranging from 38°C to 43°C are used for balneotherapy. The Tramutola test site is located on the western side of the Agri Valley (Basilicata region) which hosts the largest onshore hydrocarbon reservoir of Western Europe. During the drilling of the "Tramutola2" well (404.4 m) in 1936, a significant volume of sulphureous hypothermal water (28 °C with a flow rate of 10 l/s) with accompanying gases (mostly CH4 and CO2) was discovered.

At the same time, TOGETHER project aims to develop and apply communication methodologies devoted to increasing the acceptance of the exploitation of geothermal energy. This objective will be accomplished by actively engaging local communities and younger generations, who will serve as the foundation for scientific education, social interaction, and constructive debate.

How to cite: Amoroso, O., Giampaolo, V., Balasco, M., Blasone, M., Bubbico, D., Capuano, P., De Martino, G., Gargiulo, M. V., Napolitano, F., Perrone, A., Panebianco, S., Russo, R., Serlenga, V., and Stabile, T. A.: Sustainable geothermal energy for two Southern Italy regions: geophysical resource evaluation and public awareness , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12849, https://doi.org/10.5194/egusphere-egu24-12849, 2024.

X4.176
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EGU24-13959
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ECS
Gi-Yi Huang, Bieng-Zih Hsieh, Kenn-Ming Yang, Tien-Kai Tang, Mu-Hsun He, Cheng-Yueh Wu, Guo-Teng Hong, and Wan-Chung Lu

Renewable energy is a sustainable and clean with no (or very few) carbon dioxide emissions. Geothermal energy is a renewable energy, it uses the geo-heat from the Earth and can generate a base-load electricity. Taiwan aims to achieve zero-emission by 2050. For this target, geothermal energy plays a crucial role to help Taiwan make the goal of zero-emission electricity possible.

Taiwan, located at the Pacific Ring of Fire, has abundant geothermal resources. The estimated conventional geothermal potential in Taiwan is about 989 MW. In which, The Tatun Volcano Group (TVG) in northern Taiwan has the most conventional geothermal potential of over 500 MW. The investigation and development of geothermal resources in the Tatun Volcano Group is important for the development of Taiwan's geothermal energy.

The purpose of this study is to conduct a geothermal resource investigation in the Mt. Shamao area a located in the Tatun Volcano Group in order to apply the information for the next-step exploration well drilling. This research establishes a three-dimensional geothermal conceptual model by geothermal geological surveys and estimate the geothermal resources based on the developed conceptual model.

 

This study primarily involves initiating field geological investigations to explore the lithology of the geothermal reservoir and potential structures and fractures in the Mt. Shamao area. Based on the rock types recorded during field geological investigations and subsurface geological interpretations, we aim to establish a geothermal conceptual model for the region. Additionally, a three-dimensional geothermal geological model will be developed for heat storage assessment.

Field investigation is used in this study to explore the lithology of the targeted geothermal reservoir as well as the potential structures and fractures in the Mt. Shamao area. By combining the findings from the field investigation and the subsurface geological interpretations from the neighboring existed deep wells, the geothermal conceptual model is established. All information is integrated in a 3-D model built in the GOCAD simulator. Based on this 3-D model, the geothermal resources is estimated by a numerical simulator, CMG STARS.

 

The geological model of Mt. Shamao area is built  based on  previously and newly reconstructed geological profiles, lithological well logs, DEM data, regional fracture and structural lineament data, and lithofacies descriptions in the field. This area is characterized by numerous high-angle faults, which may serve as effective geothermal conduits. The geological model shows andesite of about 750 meters overlying sandstone-rich formations in the Mt. Shamao area. From the temperature records of nearby deep wells, the highest temperature is in the andesite reaching 174°C, and the maximum temperature is 240°C found in the sandstone formation.

Based on the constructed geological model and the temperature log of existed wells, the natural state model for the Mt. Shamao area is established from the numerical simulation method. The storage heat capacity is estimated for the area of about 12 square kilometers with the thickness of 5 km. By considering the development period of 20 years, the estimated power potential of Mt. Shamao area is over 200 MW from the volumetric method.

How to cite: Huang, G.-Y., Hsieh, B.-Z., Yang, K.-M., Tang, T.-K., He, M.-H., Wu, C.-Y., Hong, G.-T., and Lu, W.-C.: The Geothermal Conceptual Model and Resource Assessment of the Shamao Mountain Geothermal Potential Area in the Tatun Volcano Group (TVG), Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13959, https://doi.org/10.5194/egusphere-egu24-13959, 2024.

X4.177
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EGU24-19473
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ECS
Majdi Al-Howidy, Hartwig von Hartmann, Mehrdad Soleimani Monfared, and Inga Moeck

The North German basin characterizes challenges and unique opportunities of the geothermal reservoir because of the geological structure and geothermal potential. One of these challenges is the marine environments of Eocene deposits. This contains shallow marine environments where can changing sea levels lead to a variety of sediments from coastal sands to deep marine clays. Moreover, the uncertainty of reservoir features due to diagenetic processes over geological time can considerably change the original depositional characteristics of sediments. This study outlines a comprehensive investigation focused on classifying and analyzing shallow to medium-deep geothermal plays, mainly within the Brussels sand formation from the Tertiary sediments in the middle Eocene. We have selected this formation due to its appropriate thickness for geothermal reservoir studies and its lithological characteristics, previous studies have shown that the sediment sequence contains shale and sandy formation in Wilhelmshaven with a thickness of around 5 -130m. The approach that we are going to present in this study, leverages a combination of Geothermal, well, petrophysical well logs, and seismic data to build a rock model and perform a geothermal reservoir characterization in the area. A comprehensive investigation of the North German Basin's geothermal potential has been conducted, with a focus on the classification of play types. This classification is essential for understanding the range of geothermal systems present and their particular characteristics. The first stage contains the selection of areas with a geothermal potential based on the thickness of the formation, depth of the target formation, availability of 3D seismic data, the density of drilled wells, and the thermal gradient. Through a primary analysis and literature review, based on the aforementioned parameters, the sand bodies of the Brussels Formation were shown to be a suitable target for further exploration. Then it follows by a detailed analysis of underground temperatures of reservoirs in medium-deep depth. The dominant temperature of the geothermal reservoir in this depth and the selected target formation is expected to be classified as low, which can be suitable for heating purposes. These lower-temperature reservoirs are suited for district heating systems, especially when combined with heat pump technology. Heat pumps can raise the temperature of the geothermal heat to stages suitable for domestic and industrial heating. Then the integrated workflow of the temperature analysis and rock model investigation in this study can assist as a foundational framework for further detailed reservoir engineering studies and further economic assessment.

How to cite: Al-Howidy, M., von Hartmann, H., Soleimani Monfared, M., and Moeck, I.: Integrated geothermal reservoir characterization in the North German Basin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19473, https://doi.org/10.5194/egusphere-egu24-19473, 2024.

X4.178
|
EGU24-19773
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ECS
Malte Ziebarth, Michael Drews, Florian Duschl, Indira Shatyrbayeva, Oliver Heidbach, and Birgit Müller

Advance information about local pore pressure distribution is crucial for the drilling of deep geothermal wells. Incorrect adjustment of the drilling mud density leads to drastic differences between wellbore pressure and the ambient pore pressure. Large pressure differences may result in severe drilling problems such as kicks, wellbore instabilities and subsequent partial or full loss of the previous borehole progress. In particular for small geothermal ventures on a communal level, this loss may pose a significant financial risk.

We present current work on EFECT, a tool that helps to organize existing pore pressure measurement data and to generate geologically informed pore pressure estimates based on these existing data. EFECT integrates geographic information system (GIS) components that allow the user to explore pore pressure data sets and select offset wells for a planned well location. As a first step, the regional aggregate pore pressure model shows general features of the regional pore pressure with depth. The core feature of EFECT is the projection of the offset wells’ pore pressure to the target well based on matching stratigraphic units. Two projection algorithms are provided that assume either (1) overpressure or (2) vertical effective stress is constant between target and offset wells.

EFECT is part of a larger effort to develop a global pore pressure database with a standardized quality ranking. The data from this database, consisting of pore pressure measurements and indicators such as well tests, kicks and mud weight data, provide a standard that users may augment with their own data. This standard data set can be particularly useful for small geothermal ventures. We illustrate EFECT using data from a precursor of the global pore pressure database covering the SE German part of the North Alpine Foreland Basin (Bavarian Molasse Basin).

How to cite: Ziebarth, M., Drews, M., Duschl, F., Shatyrbayeva, I., Heidbach, O., and Müller, B.: EFECT: A tool for pore pressure projection and data management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19773, https://doi.org/10.5194/egusphere-egu24-19773, 2024.

X4.179
|
EGU24-21715
Yifei Xing

Xiongan New Area is located in the middle of North China Plain, with high background heat flow values and abundant geothermal resources. However, the degree of development of geothermal resources in Xiongan New Area is different, and the understanding of the hydrochemical formation and evolution is not comprehensive. Geothermal water and cold groundwater in Rongcheng uplift, Niutuozhen uplift, Baxian depression, Baoding depression and Gaoyang low uplift were sampled for hydrochemical analyses. There are two types of thermal reservoir in the study area: sandstone and karst thermal reservoir. Minghuazhen formation and Guantao formation had relatively shallow buried depth, and the hydrochemical types were mainly Cl·HCO3-Na and Cl-Na type. The main hydrochemical type of Wumishan formation was Cl·HCO3-Na. Due to the high degree of homogenization of karst reservoir, the spatial difference of hydrochemical characteristics was relatively small. From shallow to deep, the TDS value of geothermal water increased. Due to the influence of the water conduction in the fault zone, the mixing phenomenon of geothermal water in some deep Wumishan and Guantao formation occurred. The metamorphic coefficient and desulfurization coefficient of geothermal water in Wumishan formation were lower than that of Guantao formation, and the thermal storage was relatively closed and in relatively reduced state, while the sealing of geothermal water in Guantao formation and Minghuazhen formation was relatively poor. Our result is of great significance to understand the geothermal resources in Xiongan New Area and to promote the clean heating in winter in northern China.

How to cite: Xing, Y.: Analysis on the Chemical Field Characteristics and Influencing Factors of Geothermal Water in Typical Area of North China Plain , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21715, https://doi.org/10.5194/egusphere-egu24-21715, 2024.