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STAGES OF SELECTION OF THE COAL RESOURCES BASE FOR UNDERGROUND GASIFICATION - ON AN EXAMPLE OF THE LUBLIN COAL BASIN (POLAND)

E. Sermet

Abstract

The Lublin Coal Basin (LCB) is situated in the eastern part of Poland. Bituminous coals occur in Carboniferous Layers under the thin overburden built from Jurassic, Cretaceous and Neogene sediments. Most attractive seams (8 -12 to 18 balanced seams), with the mean thickness of about 1,3 ? 1,7 m (rarely under 2 ? 3 m) appear deep, most often at depth 750 ? 1000 m. They are cut by rare net of faults. Within the surface 1 200 km2 eleven deposits were documented, of which the only one is exploited. Total resources of undeveloped deposits are about 8 800 mln tonnes.Undeveloped deposits were included in the analysis of the applicability of the underground coal gasification (UCG) method using boreholes drilled from the surface. The most reasonable criteria for pre-qualification for UCG usefulness is thickness of the coal seam exceeding 1,5 meter. At lower thickness, the efficiency in the gasification process quickly decreases and the calorific value of the obtained gas decreases as well. UCG process can basically include sub-bituminous or low rank bituminous, flame or gas-flame coal. The important factor in the safe gasification is the tight isolation of the coal seam and its occurrence a minimum 100 meters below the flooding Jurassic and Cretaceous overburden. Seam parts limited by faults of supralocal significance should have at least 1,5 km2 surface area and the distance of the gasifier from faults must exceed 50 meters. Applying the criteria, in the initial qualification stage resources in undeveloped deposits of the LCB are approximately 846 mln tonnes, it means almost 10% of the inferred and indicated resources, dispersed (43 parcels) within the limits of large-seamed deposits. These coal seams are often characterized by complicated structure and the occurrence of intercalations. In the second stage, the additional criteria were considered ? e. g. requirements of the rational deposit development and mutual location of the coal seams in relation to aquifers. Among the indicated earlier 43 parcels, only 19 areas with 579 mln tonnes resources were left for further qualification. Considering in the next stage the environmental limits the potential resources useful for UCG are estimated for 260 mln tonnes. In the final qualification only three regions with resources of over 10 mln tonnes (each part) were selected, in which the process can be carried out without creating threats for the exploitation of the other deposits conducted by conventional methods. Resources intended for better exploration, e.g. by dense network of boreholes, are about 38 mln tonnes. Expected measured reserves are not more than 20 mln tonnes. Applying the UCG method in the LCB will only be possible on the limited scale. There is no possibility to use it as alternative or complementary method for traditional, underground coal exploitation.

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DOI resolver: doi.org/10.5593/sgem2019/1.1/s01.066

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