Example of thermal water utilization in the Czech Republic

Fig. 1: Site location.

Utilization of thermal water in the Czech Republic is a very nice example of geomanifestation. Exploration work for oil in southern Moravia (Fig. 1) in 1990 led to a discovery of a natural thermal mineral water, in depth of 1,450 m. The yield of this source is 74 l/s; the water temperature is 46 °C, and it is of the Na-Cl type, containing about 10 mg of hydrogen sulfide per liter, thus achieving unique quality in the Czech Republic.

Chemical composition of the geothermal water from the well MU3G (13. 11. 1990)
Chemical composition of the geothermal water from the well Pa2G (30. 1. 1995)

By the decree of the Ministry of Health of the Czech Republic No. 290/1998 Coll. dated 26 November 1998, the Ministry of Health of the Czech Republic declared the Mušov-3G spring as a natural curative source. It is evaluated as a naturally mineralized sulfuric mineral water of sodium chloride type, with increased fluoride content, thermal, hypotonic. This water contains dissolved methane-nitrogen gas.

The water is used by the hotel Termal and by the aquatic center Aqualand Moravia for their swimming pools and wellness center. Thanks to its unique composition, it has positive effects on blood circulation to the skin and sub cutis, locomotor system, immunity, bone structure, metabolism, autonomous nerve function, skin diseases, as well as chronic yeast and fungal diseases.

Borehole MU3G
This borehole (Figs. 2-4) was drilled to verify the horizons of the Mesozoic and the use of geothermal energy. The drilling of MU3G took place from November 26, 1989 to February 19, 1990. Its depth is 1455m and the altitude is 184.11 m. The perforated sections are from 1204 to 1418 m. Artesian sources with temperature 46°C were encountered at depth ranges of 1203.7-1362.2 m and 1373-1418.2 m (ca. 7 l/s).

Profile of the borehole MU3G
The surface part contains Miocene (Carpathian – Eggenburgian) represented by clay – sandy layers; the top of the complex is formed by is sandy facies, the central part is represented by clay facies, and the bottom is formed by sandy layers.

The carbonate development (Mesozoic – Jurassic) is represented by limestones, changing to detritic limestones. Further down the profile dolomitized limestones follow. In the basal part we can find frequent occurrences of cherts, and further towards the bedrock there are dolomites that conclude the entire carbonate development.

The Jurassic is present in the basal clastic formation by gray, fine-grained, mica, quartz sandstones. Fundament (Cadomian age) is formed by granites of the Brno Massif.

Borehole Pa2G
The borehole Pa2G was situated on the northern outskirts of the village Pasohlávky about 2.6 km from the borehole MU3G (see Fig. 5). This borehole was designed as a reinjection borehole, which will serve as a re-injection of already thermally used geothermal water from the MU3G borehole. Today it serves as a geothermal well. The drilling of the borehole started on 1 December 1994 and the set of related various hydrodynamic measurements was completed on 10 May 1995. The borehole depth is 1200 m and the altitude is 186.08 m. The water temperature at the borehole is 40 °C. The borehole perforations were made at depths: 712.6 – 723.2 m, 780.1 – 791.7 m, 1063.2 – 1074.7 m, and 1104.6 – 1116.3 m. Artesian overflows were encountered at depths of 713 m, 1064 m, and 1130 – 1140 m.

Profile of the borehole Pa2G
The surface rocks consist of Miocene (Carpathian – Eggenburg) sediments. Further to the basement lies the Jurassic carbonate facies (Malm – Oxfordian, Tithonian). The upper part of the carbonate facies is formed by the carbonate platform whereas the bedrock is characterized by the pelite-carbonate platform. The facies is represented by limestone to dolomitic limestone. The Jurassic Dogger sediments, which are represented by Gresten sandstones and claystones, underlie the carbonate development of the Jurassic. The fundament is formed by granites of Cadomian age.

Fig. 5: Geological map

Aleš Havlin
CGS, Czech Geological Survey
– Česká geologická služba

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