Geotermal resources of Ukraine

Abstract

Geothermal resources ( W ) are quite a novel type of extractable resources. Their consumption, however, is among the world’s fastest growing power industries. Our evaluations of W were largely focused on 1) resources that can be used for heat supply, 2) on the extraction, with the help of a geo-circulation system (GCS), of water at a temperature ( T ) of at least 60 °C, and 3) on its (water) release back into the Earth at T = 20 °C. Economic appraisals point to a plausible achievement of commercial viability (provided that the most efficient technologies are employed) starting from the geothermal gradient equaling 0.02—0.025 °C/m ( W = 2.5 tons of standard fuel per m2 (t s.f./m 2 ) with the drilling to a depth of 6 km). Calculations were performed not just for the depth of 6 km, but also for the drilling depths of 3 and 4.5 km. It has to be mentioned that the estimated W magnitude is not exhaustive as regards heat reserves within the Earth. After the energy has been extracted from the depths of 5.5 to 6 km, it can be further recovered from shallower depths. In the Dnieper-Donets basin (DDB), for example, he-at reserves estimated with the help of the formula for 6 km can be increased by a factor of 4.5 if other depth intervals are also exploited. To calculate W the mean rock thermal conductivity values (1.7—2.65 W/m × °C) were used. W was calculated for all the 5,500 sites with known values of deep-seated heat flow. The contour interval was approximately matched with the double error in the W determination. The maps show that cost-effective fossil fuel energy resources abound in three large basins: western, eastern, and southern. In central Ukraine, they only occur within small areas. Yet, the said territory, largely the Ukrainian Shield and its flanks, is least covered by studies in terms of the deep-seated heat flow. Marketable resources have been found within the only well-explored portion of the area (at the center of the shield and its northeastern margin). The richest W resources amounting to 10 t s.f./ m 2 have been located in Transcarpathia’s (TC) western basin. This estimate exceeds reserves of major deposits of oil or gas. But the average W (hereinafter referring to the drilling depth of 6 km) is about 3.5—4 t s.f./m 2 . The total amount of energy in the basin is about 0.2 trillion t s.f./ m 2 . High W in the eastern basin has only been recorded in isolated areas of the Donbas (5—7 t s.f./ m 2 ). In the main part of the DDB, W equals about 3 t s.f./ m 2 . Therefore, the average W value for the basin is 3—3.5 t s.f./ m 2 . The total estimated resources come up to about 0.3 trillion tons of standard fuel. In the southern basin of the central Crimea W reaches 7—8 trillion tons of standard fuel per m2, but on the considerable part of the territory W is about 3—4 t s.f./ m 2 . The composite amount of energy in the basin is about 0.3 trillion tons of standard fuel. Ukraine’s total fossil fuel resources (as discovered to date) within the depth range of 5.5—6 km are 20 times higher than all fossil fuel reserves on its territory. Minimal amounts of fossil fuel resources suitable for the production of steam electricity without additional heating can be found with the drilling depth of 4.5 km only in some parts of TC. With the drilling depth of 6 km, the re-sources might reach commercial level in TC and in isolated areas of the Crimea and the Donbas.