Dominant Permeability Direction and Its Influence on Gas Drainage of Ⅱ1 Coal Seam in Guhanshan Coal Mine

Through the observation statistics of Guhanshan Coal Mine coal seam fractures, the coal fracture opening and closing control features is analyzed, eastern gas geological unit N50°E to fracture group affected by in situ stress relative tension, the western gas geological unit N30°E to fracture affected by the relative stress and tension in and prediction of mine gas geology units of the eastern, the western gas geological unit of coal seam permeability advantage range is N50°E, N30°E, respectively. Field test results show that the coal seam permeability presents anisotropic distribution, along the N55°W direction, the measurement of borehole permeability value is far greater than in the other direction, the advantage distribution range of coal seam permeability is N35°E, the results of field tests and coal seam permeability advantage range prediction is consistent. In view of the permeability distribution characteristics of Ⅱ₁ coal seam, the influence of hydraulic fracturing, acidizing coal seam and other measures on the permeability of coal seam is discussed. The optimal gas mine gas extraction solution is proposed, namely, eastern gas drainage by drilling design should be vertical to N50°E, and western gas drainage by drilling design should be vertical to the N35°E.