ON THE INFLUENCE OF FILTRATION AND MICROPORES ON THE GAS-DYNAMIC PROPERTIES OF COAL SEAMS

Purpose: to establish the closeness of the correlation between the volume of filtration pores of fossil coals for coal seams of the Donetsk and Lviv-Volyn basins with the degree of their metamorphic transformations. Methodology: the research methodology involves statistical processing by the least squares method of the values of total porosity, micropores and filtration pore volume, and establishing their empirical dependencies on the yield of volatile substances. Comparing indicators of the closeness of correlations between empirical curves and experimentally determined values of pore volumes allows us to establish the stages of formation of different types of pores. Results: Based on statistical processing, empirical dependences of the indicators of the volume of total porosity, micropores and filtration pores on the degree of metamorphic transformation of coal seams were obtained. Filtration pores, with volumes similar to or equivalent to micropores, were formed at earlier stages of coalification compared to metamorphism. As a result, there are no close correlations between the volume of filtration pores and the output of volatile substances. Approximately equal ratios were established between the average values of the volumes of filtration pores and micropores for the entire set of 776 coal seams. At the same time, the ranges of changes in micropores are significantly narrower than filtration ones, which indicates a purely individual relationship between the volumes of filtration pores and micropores, regardless of the degree of metamorphic transformations of a particular coal seam. Micropores determine the possibility of methane being in the main sorbed state, while filtration pores determine the possibility of methane being in a free state. The ratio of these forms of methane in coal, to a greater extent, in comparison with the metamorphic transformations of coal seams, is obviously characterized by their tendency to manifest gas-dynamic phenomena. Scientific novelty: for the first time, based on statistical processing of experimental data, the formation of micropores has been proven, mainly at the stage of metamorphic transformations of coal seams. This is confirmed by the close correlation between the volume of micropores and the release of volatile substances for a set of 776 coal seams. The obtained dependence is characterized by high values of the coefficient of determination and a relatively low root mean square deviation. Practical value: the research results make it possible to develop proposals for improving the regulatory framework for safe mining operations in terms of predicting the manifestation of hazardous properties of coal seams. Keywords: pores, volume, coal seams, hazardous properties, metamorphism, forecast, improvement.