Proceedings World Geothermal Congress 2005 Antalya, Turkey, 24-29 April 2005 1 Estimates of Geothermal Resources in Belarus and the Country Update Vladimir I. Zui and Diana A. Mikulchik Institute of Geological Sciences, Kuprievich str., 7, 220141 Minsk, Republic of Belarus. E-mail: zui@igs.ac.by; diana@igs.ac.by Keywords: Geothermal Energy, Geothermal Resources, Geothermal Potential, Belarus. ABSTRACT The energy supply industry in Belarus is based mostly on the use of different kinds of fossil fuels (gas, oil, coal). Smaller percentage of energy production is based on the use of local fuels (peat, firewood, wood chips, etc.). Installations to use wind and solar energy as well as biomass to generate electricity are still at the experimental stage. There are no nuclear electric stations in the country. Therefore, Belarus is dependent on the energy import from neighbors, first of all, of the natural gas and crude oil supply from Russia.. The country produces itself only around 20% of the annual consumption of raw oil and a few percents of requested natural gas. Therefore the problem to increase the utilization of local sources of energy, including its renewable kinds is evident. The geothermal energy belongs to them and is available in the subsurface within practically the whole territory of Belarus. But the most promising areas for the underground heat extraction are the Pripyat Trough and the Brest Depression, located in the southeastern and southwestern part of the country, respectively, Zui, Levashkevich (2000); Zui et al. (2002). Resources of the geothermal energy are dependent on a number of parameters. Depths to geothermal horizons, the ambient temperature of rocks, the composition and content of dissolved chemicals within these reservoirs are the primary factors, influencing both the estimated geothermal resources, and technical possibilities of their exoploitation. The deeper the geothermal horizon within the platform cover, the higher is its temperature and the higher is the dissolved chemicals content of warm groundwater and brines, saturated rocks. For instance, the latter parameter is the most critical one complicating the geothermal resources exploitation from deep geothermal horizons of the Pripyat Trough both from technological and economical points of view. 1. GEOLOGICAL BACKGROUND A junction of geologic units of different age and origin takes place within the territory of Belarus. Three deep sedimentary basins exist in the northeastern, southeastern and southwestern parts of the considered area. They are the Orsha Depression, Pripyat Trough and the eastern part of the Podlyaska-Brest Depression, respectively. The main part of the latter one is stretched into the territory of Poland and only its easternmost margin is traced in southwestern Belarus, Fig.1. The Pripyat Trough is the deepest sedimentary basin within the territory of Belarus. Its crystalline basement is subdivided into many blocks by deep faults, which is reflected in variable depths of them. In turn, its platform cover has a complex geological structure with two salt bodies of the Devonian age. The Intersalt deposits separate the Upper Salt and Lower Salt complexes within the trough. The total thickness of the platform cover varies in a wide range from 0.5 km at the margin with the Polessian Saddle till 5.0 – 5.5 km along the southern marginal fault, separating the trough from the Ukrainian Shield, and the northern limiting fault, separating it from the Bobruisk Buried Inlier, North-Pripyat Arm and the Zhlobin Saddle. The Bragin-Loev Saddle joins the Pripyat Trough with the Dnieper-Donets Depression, the main part of which is located in the territory of the Ukraine. Figure 1: Main geological units within the territory of Belarus; Geology (2001), modified. Legend: Borders and structures: 1 – the largest, 2 – large, 3 – medium. Platform Faults: 4 – super regional, 5 – regional, 6 – sub regional and local. Abbreviations: BBI – Bobruisk Buried Inlier, ChSB – Cherven Structural Bay, DDD – Dnieper-Donets Depression, KG – Klintsy Graben, MM – Mogilyov Mulde, NPA – North-Ptipyat Arm, SBI – Surazh Buried Inlier, VM – Vitebsk Mulde, ZhS – Zhlobin Saddle. The lower geothermal horizon of the trough is related to Devonian sediments overlying the crystalline basement and underlying the complex of the Lower Salt. Its depth reaches sometimes 4.5 –5.5 km depending on the considered basement block. Temperature values range here from about 70 till 110-120 ˚C. A stagnant regime exists here, brines filling the pores and cracks in rocks have the dissolved chemicals content up to 400-420 grams per liter (g.p.l.), Kudelsky, et al. (1985). The intersalt deposits separate the Upper Salt and Lower Salt complexes within the trough. The depth to their roof is on average 2.0 –3.0 km. High salinity brines were observed within this complex. The content of dissolved chemicals here is lower than in the sub-salt geothermal horizon, but still reaches on average up to 180-300 g.p.l. A thickness of the permeable intersalt deposits ranges from 100 meters in the western part of the area up to 1000 meter observed in a few wells of the southern and southeastern parts.