Geodynamical Events (Coal-and-Gas Outbursts) in the Donets Basin, Ukraine

Abstract

Optimization of production and effective management of mining hazards are in large part dependent on knowledge of geological, particularly structural properties of the mining medium. Over the past decade in the Donbas 1550 gas-geodynamic events, including 38 sudden instantaneous coal-and-gas outbursts, were recorded during underground mining. Coals of specific rank and mining depth with high initial desorption rates are traditionally considered prone to instantaneous outbursts. However, other factors such as in-situ stress, petrographical composition and structure of the coal, location and orientation of geological discontinuities, and elastic properties of the medium were also demonstrated to be important. It has also been observed that small-scale gas-geodynamic events, which tend to occur at the mining face, are typically unrelated to geological structure, whereas larger events are structurally controlled as they are preferably located along tectonic zones. The stress discharge at such localities is dangerous already in terms of levels of energy released, but additionally it also liberates gas from adjacent collectors, like fault gouge reservoirs or gas sorbed on microporous coal surface. While considerable effort was invested in developing prediction techniques, unexpected geodynamic incidents resulting in fatalities continue to be a major concern for underground coalmining.