Study on Gas Extraction Technology of Vertical Long Directional Drilling in Coal Seams Group
Aiming at the problem that a large amount of pressure-relieved gas from adjacent coal seams pours into the first mining face in the mining of high-gas close-distance coal seam group,the distribution and evolution law of mining-induced frac-tures in close-distance coal seam group were revealed by means of numerical simulation and field measurement,and the technical scheme of three-dimensional long-distance directional drilling gas extraction in coal seam group was proposed.In this paper,ac-cording to the field conditions of a mine test face,the technical parameters of the layout of three-dimensional long distance direc-tional gas extraction borehole in the upper,middle and lower strata are determined.The field application results show that during the observation period,the average concentration and purity of gas extraction in the roof long distance directional drilling are 48.9%and 0.71 m3/min,respectively.The average concentration and purity of gas extraction in the coal seam gas extraction pipe-line are 20%and 6.73 m3/min respectively.The average gas extraction concentration and purity of long directional borehole in floor are 40%and 0.43 m3/min,respectively.
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