Development of a Hydrodynamic Method for Degassing of Gas-Saturated Flat-Lying Coal Seams

Deterioration of geological and mining conditions for underground extraction of coal deposits with increasing depth leads to significant gas release into mine workings, reaching 45 m³ or more per 1 ton of coal mined at some mines. Existing standard methods for degassing of stressed coal seams often do not provide required degassing efficiency of 50 % and more for rhythmic operation of production faces. In some conditions, open-hole degassing efficiency of 30 % can be achieved, which allows to increase output per face up to 1,000 tpd with gas release from seam up to 5 m³/min. However, at depths of 1,000-1,300 m and high-performance operation of longwall sets of equipment, gas release can reach 170 m³/min that causes face stoppages due to gas hazard and slows down the pace of stope development and stoping. In addition, preliminary seam degassing requires rather long time. Modem achievements in the field of rock hydraulic fracturing are the basis for the development of low-energy safe and environmentally friendly technologies for degassing of stressed gas-saturated coal seams. The paper presents the findings of our studies on hydrodynamic action (HDA) on a gas-saturated flat-lying coal seam and the developed method for degassing and reduction of gas-dynamic activity of stressed coal seams in mine workings. Chemical interaction of some coal free radicals with water molecules and hydrolysis products has been revealed, resulting in formation of stable compounds. This leads to decreasing concentration of coal paramagnetic centers (PMC) and sorption activity. Our mine tests have for the first time found hydrodynamic effects on geotechnical and gas-dynamic processes in a coal mass during formation of a zone of intense gas release. Technology and layout for hydrodynamic action-based degassing of gas-saturated flat-lying coal seams have been developed, providing for spatial and time separation of seam degassing and coal extraction processes.

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