Coal Massifs Gas Permeability


Conditions and special features of methane release from the gas-bearing coal massifs into preparatory workings or preliminary degassing wells are given in the paper.

The results are presented related to studying gas permeability of the coal seams and indicators of their gas recovery into the seam workings and wells at the depths of 270–560 m from the earth surface at the gas pressures of 1.39–4.60 MPa, and the coal methane content of 14.0–21.4 m3/t. Studies were conducted on the workings extended from 60 to 1200 m during their sinking in the conditions of 17 shallow mines on 28 coal seams, 15 of which were worked out with the use of preliminary degassing.

It is established that the gas permeability of the Kuzbass coal seams varies within 0.005–0.045 milli Darcy. The intensity of methane release from the wells ranges from 2.7 to 20.1 m3/day with a coal bed capacity of 1.5–3.7 m, initial methane release into pre-degassing wells of 0.24–0.48 m3/(m2 per day), the rate of methane release reduction in time of 0.008–0.012 days–1. The relationship is noted between the quantitative indicators of gas recovery of the coal massifs in degassing wells and in reservoir workings in the dredging field.

Linear dependence in time of the inverse magnitude of the intensity of methane release into the wells of preliminary degassing of the coal seam and reservoir workings at the excavation site (K-factor) is revealed. Its numerical values for 7 Kuzbass coal seams were: 0.014–0.062 m2/m3 when methane was released into preparatory workings and 0.021–0.042 m2/m3 — into pre-degassing wells. Close numerical values of the K-factors allow to use them together in predicting the parameters of methane extraction in the projects of preliminary degassing of coal-bearing formations by the wells drilled in the plane of the coal-gas massif.

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DOI: 10.24000/0409-2961-2021-12-13-17
Year: 2021
Issue num: December
Keywords : coal seam methane release degassing methane well gas permeability intensity K-factor