RemSik

GEOTHERMAL COUNTRY UPDATE FOR

Anton RemSik Fendek

Institute of Geology, Bratislava

Keywords: geothermal energy, prospective areas. geothermal ones "C) while medium-temperature sources (T = wells 100 "C) are rarer and high-temperatures (T 150 "C) are least frequent. Abstract. The distribution of aquifers with geothermal waters and the thermal manifestation of geothermal fields in Slovakia RESEARCHAND EXPLORATION has enabled the definition of 26 prospective areas and structures with potentially exploitable geothermal energy Research, prospecting and exploration of geothermal sources. In 1971 1994 a total of 61 geothermal wells were waters has far been carried out in 13 prospective areas in drilled. They verified of waters with temperature 20 Slovakia (Fig. 1 1 , 2, 6, 9, 1 1 , 12. 13, 19, 20, 21, 92 "C. The total thermal energy potential of geothermal 26) and in one unprospective area (southern part of the Eastern waters in all prospective areas amounts to Slovakian basin - a unsuccessful well). In 1971 1994 (Table 2) a total of 61 geothermal wells were drilled (only 4 of them were unsuccessful) which verified of waters whose temperature varies from 20 to 92 Thermal capacity of these geothermal waters amounts 1 . HYDROGEOTHERMAL CONDITIONS to (water temperature will be reduced to 15 during exploitation). Geothermal waters were captured by wells The geological structure of the West Carpathiansin 210 to 2605 m deep, and their free outflow mostly ranged from Slovak territory and favourable geothermic conditions create 5 to 40 (RemSik, 1993). Chemically, the waters are repre- a suitable setting for the occurrence of geothermal energy sented by and types. their sources. The distribution of aquifers with geothermal waters T.D.S. is 0.7 20.0 and the thermal manifestation of geothermal fields in Slovakia The evaluation of the thermalenergy potential have made it possible to define 26 prospective areas and of geothermal waters in Slovakia's individual prospective areas structures with potentially exploitable geothermal energy is given in Fig. 1 . The total TEP of geothermal waters in all sources (Fig. 1 ) . These include mainly Tertiary and prospective areas amounts to Reserves of geother- intramontane depressions situated in the Inner West mal waters account for and their resources for the Carpathians (south of the Klippen Belt). remaining (renewable TEP). It is worth mentioning The temperature and heat flow density of geother- that. because of the distribution of the prospective areas, these mal fields are highly variable. At a depth of m, tempera- energy sources should be regarded as disseminated. tures range from 20 high block) to more than 70 (Eastern Slovakian basin. in which the most important 3. STATE AND PROSPECTS parts are the KoSice basin, the and the structure). The geothermal gradient in the In the other prospective areas, geothermal waters Inner West Carpathians averages 37 so have not been verified by wells (Fig. 1 4, 5, 7, 10, the (Eastern Slovakian basin 60 while heat flow 15, 16, 17, 22, 23, 24, 25). but seven of them (Fig, 1 4, density 1991) varies from 50 basin) to 5, 10, 16, 17, 21, 23) have been geologically assessed for the 120 (Eastern Slovakian basin). The highest tempera- purpose of prospecting and exploration for geothermal waters. tures, geothermal gradient and heat flow density indicate that, The evaluation of these areas, based on earlier geological with regard to geothermal properties, the Eastern Slovakian information, results of oil wells and geophysical measurements basin is the most active region in Slovakia, allowed us to propose wells for geothermal waters in the Geothermal energy is related to geothermal waters individual areas. which largely occur in Triassic dolomites and limestones of From 1991 1994 the Institute of Geology Inner Carpathian nappes and, to a lesser extent, in Neogene in Bratislava compiled a geothermal energy atlas of Slovakia, sands, sandstones and conglomerates (Central depression, The atlas consists of maps. cross-sections, graphs and dia- Horn6 . graben, Dubnik depression) or in grams which, along with a text provide a good review of the Neogene andesites and related pyroclastics spatial distribution of the earth's heat (hot dry rock), geothermal ce). These aquifers lie at depths of 5000 m (except in waters and TEP in Slovakia. A geothermal map of Slovakia spring areas) and the temperatures of their geothermal waters at scale is ready for printing. range from 20 240 "C. Two wells for geothermal waters are currently being As far as temperature is concerned, geothermal drilled and a third one is being prepared in the Poprad basin waters in Slovakia (Tab. 1 ) are dominated by low-temperature (Fig. 1 13). Another geothermal well is being drilled

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RemHik Tab. 1 Distribution of low- to high-temperature geothermal (RemSik and Fendek 1994)

Type and temperature of geothermal Defined geothermal water structure of area Number of waters geothermal water lures and areas

high block, Central depression of basin, basin, Trnava bay, bay, Central Siovakian neovolcanics (NW part), Central Slovakian neovolcanics (SE part), Upper Nitra basin, basin, basin, Low-temperature Liplov basin, LevoEa basin 26 T 100 pari), Horn6 graben, Rimava basin, basin, basin, Levice block, marginal black, basin, lice depression, LevoEa basin part), KoSice basin, BeSa Structure. Dubnik deoression

structure, Central depression of the Danube basin, KoSice basin, Mts., LevoEa basin (Npart), Liptov basin, Turiec basin, Central Slovakian neovolcanics (NW 16 part), basin, basin, llava basin, basin, bay, Trnava bay, Vienna basin. Komhrno block

structure, basin (part of High-temperature Central Slovakian neovolcanics NW part), 5 basin, Vienna basin, Central depression of the Danube basin

in basin (Fig. 1 area 10). Two geothermal stations REFERENCES based on earlier wells are under construction: in the Danube basin central depression (2) at and in Levice block Fendek, M. and Franko, 0. (1989).TEP a (18) (reinjection). in 0. Franko et 1989: Geotermhlna A good chance to capture geolhermal-energy may Geofond, Bratislava. also be found in those areas where geothermal waters have yet been verified by wells. Particularly promising are M. (1991). Karpat seven areas 17, 21, 23) where geological ny model Geofond Bratislava. evaluation realistically suggests new sources of geothermal energy. The most promising of them is the KoSice basin (23) RemSik, A. (1993). geotermalnej energie Slovenska a where medium- and high-temperature Sources of geothermal ich Ekologia a 2, energy suitable for electricity generation 30 can be captured a depth m there are A. energia walers at 165 "C. The Institute of Geology 98, Geol. D, Bratislava. is actively anempting verify geothermal waters KoSice basin and has compiled a geological project including A. and Fendek, M. (1992). Geological Project of a m deep pilot well (RemHik and Fendek, 1992). The Geothermal Well RGK-1 Basin. well is currently being planned. Institute of Geology. There exist further possible sources of geothermal energy in Slovakiaas geothermal waters are widely distributed and Fendek, M. (1994). energia here. In addition to above facts, it is worth mentioning Slovenska so na Procee- that 26 defined prospective areas cover more than a dings of conference Jan Geologic Days. In press. quarter (27 of Slovakia's territory.

317 Tab. 2 Results of geothermal u e l l s d r i l l e d i n 1971 1994 i n Slovakia and Fendek,

s t r u c t u r e of l i n g Aquifers Oepth of Discharge Uater neat Chemical type of geother- period perforated temperature waters mal wells intervals (over 20 of 100 i o n sun t o t a l )

1972- 1990 Triassic dolomites, 0.7-90.0 block limestones, Neogene Na- Cl sands. conglomerates type

Central 1971-1990 Neogene sands. sand- 276-2487 stones, Na-Cl

1989- 1 Badenian sandstones, 745-1905 1.5-15.0 * 52.0-75.0 0.25-2.40 10.0-30.0 I

Levice 1973- 1986 Badenian 995- 69.0-80.0 6.30-14.42 Na-Cl block Triassic dolomites I

'1 1989 Pannonian sands, 1509- 1700 12.0 2.50 20.1 sandstones I

1985 Triassic 1512-2025 40.0-55.0 0.33- 1.78 basin I

Triassic dolomites, 73 .O- 78.0 limestones

0.93 Upper N i t r a Triassic limestones, 26.0 66.0 4.85 3 dolomites

L i p t o v 1976- 1991 Triassic dolomites, 6.0-31.0 basin l Structure of D r i l l i n g Aquifers Depth of Discharge Uater Heat pover T.D.S. Chemical type of area geother- period perforated waters mal wells intervals (over 20 of 100 ion sun t o t a l )

3 Triassic dolomites 835-1983 20.0-33.0 basin I I I

1 Triassic dolomites 950-1565 100.0 54.0 16.3 1.2

Turiec 1 1989-1990 basin

basin 1

Eastern 1 1973 basin