GEOLOGICZNI BARIERY I OGRANICZENIA DLA PODZIEMNEGO ZGAZOWANIA WĘGLA

Abstract

BARRIERS AND LIMITATIONS FOR UNDERGROUND COAL GASIFICATIONAbstract. The possibilities of underground gasification of coal in the Polish deposits were previously overestimated. Geological conditions of coal occurrence may restrain or preclude possibility for safe UCG. According to the experimental data the minimum thickness of coal should be at least 1,5m and it is the only one criterion justified enough. The underground gasification of the Polish lignite deposits will be very difficult or impossible due to the presence of aquifers in their close vicinity, to hard coal deposits, underground gasification is restrained by: (1) friable, porous, water-bearing sandstones within coal-bearing series, (2) tectonic disturbances (faults), (3) barren partings in coal seams, (4) numerous coexisting coal seams whose simultaneous gasification may be difficult. The most important factor for safe UCG is isolation of the coal seams by a sufficiently thick seal of impermeable rocks preventing toxic gases and substances (CO, phenols) escape to the environment The minimum necessary thickness of such rocks should be close to 100 m. There should be no faults. According to the recent knowledge, there is no possibility to replace conventional underground coal mining by UCG in the Polish coal deposits. Underground coal gasification could be applied only exceptionally. Further investigations of unsolved problems of UCG application are necessary on the minimum safe thickness of undisturbed impermeable rocks surrounding coal seams, and the impact of the seam structure and coal quality on the gasification process and results.