Geothermal sites distribution and
installed capacity by administrative regions (1998)
The country is rich in low enthalpy
geothermal energy. Conductive heat flow data vary
within the interval 30-80 mW/m2, while in the hydrothermal
zones it reaches 140 mW/m2 (Sofia depression) and
200 mW/m2 in the Erma reka region (Petrov and Bojadgieva,1993).
The geological structure of Northern
and Southern Bulgaria is variegated and contrasting.
The hydrothermal systems were formed mainly during
the Alpine tectonic activity in the Balkan region.
Natural thermal springs are not found in the region
of Northern Bulgaria. Two artesian basins are located
in it - the Moesian and Varna basin. Thermal water
was discovered only in deep wells.
The southern part of the country has abundant springs
which provide drainage of nonstratified mountain
systems. The springs are developed mainly in granite
and granitoid intrusions and ancient siliceous and
metamorphic complexes.
The hydrothermal data comes from prospecting
carried out in hundreds of exploratory and production
wells, springs, ore pits and tunnels. In the ex-socialist
countries, geological exploration had extensive
budgets enabling the identification of geothermal
reservoirs, proven by wells. The depth of the hydrothermal
exploratory wells ranges from 100 to 5000 m in Northern
Bulgaria and from 100 to 1500 m in Southern Bulgaria.
http://www.geothermie.de/egec_geothernet/menu/frameset.htm
>> Status of Geothermal Energy in Bulgaria
