Properties of geothermal fluids in Switzerland: A new interactive database

doi:10.1016/j.geothermics.2008.07.001

Geothermics

Volume 37, Issue 5, October 2008, Pages 496-509

https://doi.org/10.1016/j.geothermics.2008.07.001 Get rights and content

Abstract

A database on geothermal fluids in Switzerland, called BDFGeotherm, has been compiled. It consists of nine related tables with fields describing the geographical, geological, hydrogeological and geothermal conditions of each sampling location. In all, 203 springs and boreholes from 82 geothermal sites in Switzerland and neighboring regions are listed in this new interactive Microsoft Access database. BDFGeotherm is a functional tool for various phases of a geothermal project such as exploration, production or fluid re-injection. Many types of queries can be run, using any fields from the database, and the results can be put into tables and printed or exported and saved in other files. In addition to describing the database structure, this paper also gives a summary of the reservoir formations, the geographical distribution of hydraulic parameters, the geochemical types of thermal waters and the potential geothermal resources associated with the sites.

Introduction

Many data are available on geothermal fluids in Switzerland. They were obtained from deep boreholes drilled for geological evaluations, oil exploration, geothermal prospecting, thermal spas, thermal springs and fluid outflows from tunnel-drainage systems. These data are contained in a variety of reports and papers, often not published and not easily accessible to potential users of the information (Sonney and Vuataz, 2007).

The objective of this work was to gather the maximum amount of data on deep fluids and to integrate them in a relational database. This database can be useful to all geothermal projects dealing with the exploration, production, and injection of geothermal fluids. The projects may involve permeable geological reservoirs or may be based on the technology of enhanced geothermal systems (EGS). The tool may also be used to estimate and forecast the chemical composition of geothermal fluids. The database is also of interest for studies related to the risks of mineral deposition or corrosion in boreholes and in surface installations, and also for studies on interactions between rocks and thermal waters.

Geographically, all Switzerland is covered, although the distribution of data is quite heterogeneous (Fig. 1). Additional sites outside the country were selected because they are located near the border, have hot springs, deep boreholes or geological features similar to those in Switzerland and are of geothermal interest. Geologically, each formation presenting groundwater aquifers, from the crystalline basement to Tertiary sediments, was taken into account. Moreover, all thermal and sub-thermal springs with a temperature greater than or equal to 15 °C, or between 10 and 15 °C if the mass production is high, were included in this database.

The selected parameters concern the following fields: geography, geology, hydrogeology, hydraulics, hydrochemistry and geothermal parameters. The interactive and multiparameter BDFGeotherm database was built using Microsoft Access.

Section snippets

Geographical description of sites

In Switzerland, geothermal direct use in 2006 is estimated to have reached an installed capacity of about 650 MW_th, with 5500 TJ/year of heat production, mostly in installations coupled to geothermal heat pumps (GHP). This corresponds to an annual saving of 130,000 tons of fossil fuel, and reduces the emission of CO₂ by about 400,000 tons per year (Rybach and Minder, 2007). There is also some use of deep aquifers and hot spring resources, respectively in small district heating networks and for the

Geological description of potential geothermal reservoirs

This section, based on the publication by Trümpy (1980), summarizes the geological description of potential geothermal reservoirs. Geologically, Switzerland can be divided into three parts: 12.5% of its surface lies in the Jura, 30.5% in the Molasse Basin and 57% in the External and Pennine Alps (Fig. 1). The term ‘External Alps’ refers to a pre-Triassic basement complex, affected by the Variscan (Hercynian) and older orogenies, with Triassic to Lower Oligocene sediments that were deformed only

Structure of the BDFGeotherm database

The database on geothermal fluids in Switzerland consists of 9 tables numbered from 1 to 6 and from 7.1 to 7.3, with 77 fields and 203 records corresponding to all groundwater points indexed in BDFGeotherm (see Table 1). The first two tables in the structure of the database are used to describe the geographic and geologic conditions of the sites where fluid samples have been acquired. The third to sixth tables in BDFGeotherm include quantitative data on thermal fluids, whereas Table 1

Hydraulic parameters of thermal waters

The 203 sample points recorded in BDFGeotherm have temperatures ranging from 10 °C in the Malm limestone of the Jura (Tavannes borehole; Ziegler, 1992) to 112 °C in the deep crystalline basement below the Molasse Basin (Weiach borehole; Pearson et al., 1989). Measured temperatures in thermal springs, boreholes and thermal outflows in tunnels are illustrated on the simplified Swiss tectonic map in Fig. 3 and show that the warmer waters (>60 °C) are found in deeper boreholes (>1 km), the exception

Water chemistry

Many reports and publications concern the chemistry of thermal waters in Switzerland. Regional studies can be found in Carlé (1975), Högl (1980) and Vuataz (1982), while more local or specialized works are available in Pearson et al. (1989), Hartmann (1998), Kullin and Schmassmann (1991) and Pastorelli (1999). Chemical data of selected sites that are potentially interesting from a geothermal point of view, either because of temperature or production rate, and have been included in BDFGeotherm

Potential geothermal resources

The geothermal resources in Switzerland are found in most parts of the country (Fig. 5). Well-known resources are located in the northern part of Switzerland and the upper Rhone valley. Deep fluids are used in small district heating networks and for the heating of spas. Some areas are not endowed with obvious geothermal resources, for example the southern part of the Folded Jura and the high Alpine relief, but Alpine valleys drain large amounts of water coming from the mountain slopes and may

Information about the use of BDFGeotherm

A CD-ROM containing BDFGeotherm database is available on request at the Centre for Geothermal Research (CREGE, [email protected]). Due to its size, the database cannot be transmitted by e-mail (BDFGeotherm.mdb; 408 MB) but it is possible to download it from a ftp address. This CD-ROM also contains the users’ manual (BDFGeotherm-Notice-explicative.pdf, for the time being in French only) allowing the users to introduce new information into the database. This users’ manual describes all steps to be

Conclusions

The geothermal map of Switzerland shows an important concentration of geothermal sites in the northern part of the Jura range, where they are related to a heat flow anomaly, and in the upper Rhone Valley, where they originate in deep upflow systems. In Switzerland there exist many thermal fluid occurrences with temperatures between 20 and 65 °C. Their various geochemical water types are linked to the geological formations, and the length and mode of fluid circulations.

The BDFGeotherm database

Acknowledgments

The development of the BDFGeotherm database was financed through a contract from the Federal Office of Energy (OFEN No. 101’842). The authors warmly thank the four hydrogeologists A. Baillieux, G. Bianchetti, F. Gainon and S. Wilhelm who tested the database and provided constructive comments.

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Analyzing the genesis and resource potential of orogenic geothermal systems poses significant challenges due to their complex geological backgrounds and evolutionary histories. This paper presents a novel synthesis of hydrogeochemical and isotope geochemical data, coupled with geological and geophysical results, to comprehensively understand the origins of deep, high-temperature orogenic geothermal systems. This understanding is achieved through the utilization of advanced geochemical modeling techniques to analyze the geochemical attributes of initial geothermal fluids. The hydrochemical and H/O/S isotopic composition of a total of 67 geothermal and non-geothermal water samples from the Dabie orogenic belt (DOB) were analyzed. Integrated multicomponent geothermometry (IMG) was employed to reconstruct the characteristics of the initial geothermal fluids, and PHREEQC inverse simulations creatively determined the most likely pathways of their genesis and evolution. The findings indicate that all geothermal waters from the three major geothermal fields of Luotian, Yingshan, and Yuexi are alkali-sulfate type waters. The initial geothermal fluids are acidic sulfate type with reservoir temperatures of 156–222 °C, 115–179 °C, and 100–189 °C, respectively. The primary processes responsible for the formation of these initial geothermal fluids are the dissolution of anhydrite from sulfide oxidation and, to a lesser extent, direct sulfide oxidation. Generally, the formation of geothermal systems in the investigated geothermal fields is associated with the extensional collapse and lithospheric thinning of the Dabie orogen since the Early Cretaceous Period. The spatial distribution of the three geothermal fields in this study corresponds to the tectonic-magmatic framework of magmatic intrusion-induced domes (Luotian and Yuexi) in the DOB. The reactivation of the Tan-Lu Fault during the Cenozoic Era suggests the presence of a deep heat source comprising magmatic and metamorphic components. This heat source, combined with the infiltration of paleo-atmospheric and modern atmospheric precipitation water along regional fault systems, results in the formation and gradual dilution of initial geothermal fluids. Neutralization occurs through interactions with calcite and fine-grained sodium aluminosilicates, ultimately leading to the formation of the collected geothermal water. The conceptual model established in this study elucidates the distinctive genesis and formation mechanism of the orogenic geothermal system exemplified by the DOB.
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The reliable estimation of these temperatures is a crucial task used to evaluate the energy potential available in geothermal systems (Garcia-Estrada et al., 2001; Prol-Ledesma and Morán-Zenteno, 2019; Ciriaco et al., 2020; Haklidir and Haklidir, 2020). All these investigations rely on the use of historical and latest data dealing with the chemical composition of geothermal fluids discharged either from wells or surface manifestations, which require to be recorded in global geochemical databases (Sonney and Vuataz, 2008; Kaasalainen et al., 2015; Hörbrand et al., 2018). These datasets are created to provide precise information about the geographical location, geological settings, host rocks, sampling dates, and other supplementary metadata that are commonly used for the identification of samples, and their literature sources (Diehl and Bach, 2020).
Chemical, isotopic and thermal signatures, space-temporal concentration patterns, and geochemical conceptual models are used to gather insights of the internal structure of geothermal reservoirs. These investigations rely on historical and latest data dealing with the composition of the geothermal fluids discharged from either producer wells or surface manifestations. The creation of a compositional database is based on information compiled from the sample collection and handling, and the quantification results of chemical analyses. Sometimes, this integrated task may result incomplete due to some technical issues that might generate information gaps or missing data which are struggle to control in the field and lab works. To solve the low-quality data, the missing concentration values or the significant information gaps of geochemical databases, the use of machine learning techniques has been explored in the present study. Equivalent imputation models were proposed, for the first time, to rebuild a world solute-based geochemical database which exhibited some gaps and missing data in the records of the chemical composition of fluids from geothermal production wells. The application of these models enabled that missing records to be successfully recovered by using single and multiple imputation algorithms. The imputation models were efficiently evaluated by applying statistical equivalence metrics carried out between imputed and observed (measured) data. To avoid an arbitrary use of these models, and to keep the original geochemical signatures of the fluid composition patterns, the imputed results were assessed by conventional geochemistry tools (e.g., charge unbalances, fluid classification, and some water–rock interaction footprints). Results show that single imputation algorithms that model locally provide equivalent imputation values with acceptable confidence, not only in terms of statistical metrics but also improving charge unbalances in chemical analyses of anomalous samples without altering the original water–rock interaction signatures of the geothermal systems under evaluation. In contrast, multiple imputation algorithms only tend to obtain better charge unbalances by altering the original water–rock interaction signatures. The novel use of the imputation techniques for filling geochemical databases and recovering missing data will allow a better interpretation of hydrogeochemistry modeling in future geothermal exploration and exploitation studies.
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In the USA, the U.S. department of Energy funded the implementation of a National Geothermal Data System (NGDS), which harvests data from many nodes and acts as gateway for geothermal information (Anderson et al., 2013). Research centres in Switzerland (Sonney and Vuataz, 2008), Mexico (Torres et al., 2005), Java (Setijadji et al., 2005), Nevada (Hanson et al., 2014), Germany (Agemar et al., 2014) make wide use of geothermal databases to collect and maintain information, analyse data and perform models. Geothermal databases have been developed not only at a national, but also at international levels.
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This paper describes the contents of the database and its software and data update, as well as the webGIS tool including the new tools for data lithology and temperature visualization. The geoinformation organized in the database and accessible through Geothopica is of use not only for geothermal purposes, but also for any kind of georesource and CO₂ storage project requiring the organization of, and access to, deep underground data. Geothopica also supports project developers, researchers, and decision makers in the assessment, management and sustainable deployment of georesources.

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Properties of geothermal fluids in Switzerland: A new interactive database

Abstract

Introduction

Section snippets

Geographical description of sites

Geological description of potential geothermal reservoirs

Structure of the BDFGeotherm database

Hydraulic parameters of thermal waters

Water chemistry

Potential geothermal resources

Information about the use of BDFGeotherm

Conclusions

Acknowledgments

Geothermics

Applied Geochemistry

Applied Geochemistry

Geothermie-Bohrung Pro San Gian Sankt Moritz

Bulletin der Vereinigung Schweizerischer Petroleum-Geologen und -Ingenieure

Hydrogeologische Charakterisierung der Grundwasservorkommen innerhalb der Molasse der Nordostschweiz aufgrund von hydrochemischen und Isotopenuntersuchungen

Steirische Beiträge zur Hydrogeologie

Hydrogéologie et géothermie de la région de Lavey-les-Bains (Vallée du Rhône, Suisse)

Bulletin du Centre d’Hydrogéologie de Neuchâtel

Deep groundwater circulation in the Alps: relations between water infiltration, induced seismicity and thermal springs. The case of Val d’Illiez, Wallis

Eclogae Geologicae Helvetiae

Programm GEOTHERMOVAL. Hydrogeologische und Geothermische Untersuchungen im Simplontunnel

Matériaux pour la géologie de la Suisse, Série Géotechnique

Carbogaseous spring water, coldwater geysers and dry CO2 exhalations in the tectonic window of the Lower Engadine Valley, Switzerland

Eclogae Geologicae Helvetiae

Geothermische Prospektion im Raume Schinznach Bad - Baden

Matériaux pour la géologie de la Suisse, Série Géotechnique

Die Mineral- und Heilquellen der Schweiz

Carbogaseous spring water, coldwater geysers and dry CO₂ exhalations in the tectonic window of the Lower Engadine Valley, Switzerland