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Content archived on 2022-12-27

Utilisation of geothermal waters in small basins and marginal structures

Objective

The report deals with the evaluation of the geological, technological and economic conditions of thermal water utilisation under complicated geological conditions as to be found in Thuringia. Two objectives determined the methods and the results of the survey:
1. investigation and evaluation of the possibilities of developing and utilising geothermal waters with regard to the complicated geological conditions and the low geothermal potential in Thuringia
2. recording of areas with similar conditions in the European Union and its adjacent countries, followed by a derivation of methodological conclusions for analogous investigations.

The following steps are documented in the report:
- survey of the geological conditions in Thuringia
- recording and evaluation of the aquifers bearing thermal water
- selection of potential productive horizons
- identification of perspective areas
- recording and assessment of rich sources and artesian wells
- recording and assessment of waters arising from mines
- comments on ecological, technological, legal and economic conditions for energetical and balneological use
- design outlines for the investigated sites
- recording and documentation of small basins and marginal structures in Europe
- statements about methodology and conclusions for similar investigations
The occurrence of thermal water in Thuringia depends on the principal geological structure, thus on the distribution of basement outcrops with prae- and lower-Palaeozoic series and basins with Permian and Triassic sediments. While there are only a few separated locations in basement areas, basin areas offer a wide distribution of aquifers bearing thermal water.
The Permian and Mesozoic aquifers are related to clastic sediments of the Rotliegend and Buntsandstein and to the carbonates of the Zechstein. Porous sandstones as well as oncolithical dolomites and algedolomites proved as potential layers. The following rock formations have been examined and presented in detail:
- sandstones of the permosiles
- werradolomit with rife formations
- hauptdolomites in its Randwallfazies
- plattendolomite in its enormous dolomite wall formation
- sandstones of the lower and middle buntsandstein
They show extreme vertical and horizontal inhomogenities concerning facies and water quantity. In most cases the potential for an exonomic use of geothermal energy is insufficient.
Nevertheless, there is a satisfactory potential for balneological use. The aquifers are located in a depth < 1000 m with a temperature (mean) between 20 - 30 °C. In general the resulting geothermall potential is estimated to be low.
Water flow in the basement only occurs in fractures. Thus it is only possible to explore waters of low mineralization. Areas with better opportunities are characterised by regional faults.
Due to their location (within a safe distance to water protection areas) and their direct neighbourhood to energy users, 8 out of 54 springs tested are suitable for further investigations.
After reviewing documents of 303 mines with an estimated water flow of more than 18 m3/h, 10 cases show positive results concerning the water quantity. Due to local infrastructural conditions 4 projects have good prospects for utilisation. The legal conditions have to be clarified, yet.
The low geothermal potential, an inhomogenious and decentralised user structure, strong limitations due to an intensive management of potable water and a sensible economic use of geothermal energy influence the decision concerning the location and exploration of thermal water and require intensive consideration and evaluation of all factors. Moreover, an economic use of geothermal energy in Thuringia can only be achieved by financial support. Also, this partly concerns the balneological use of the brines. Some areas in the Thuringian Basin and the Southwest of Thuringia offer possibilities for a preferably combined utilisation (balneologic / energetic). New spas planned in these areas have good prospects for developing brines.
There are 14 areas in Europe similar in geology and size to those in Thuringia. As in Thuringia the thermal-water bearing stratas are expected to be mostly younger than the higher Rotliegend (Saxon). Depending on the structural history there are differences in the sedimentary series, which are more suitable for thermal water exploitation because of a higher thickness and better hydraulic parameters. Moreover, the temperatures in these basins are higher than in Thuringia.

Call for proposal

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Funding Scheme

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Coordinator

Thüringer Landesanstalt für Geologie (TLG)
EU contribution
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Address
8 - 10,Carl-August-Allee
99405 Weimar
Germany

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