Centralized Drainage Technology and Application of Vertical Shaft in Low Permeability Thin Coal Seam Downward Drilling

Aiming at the difficult problem of centralized drainage of downward cross-layer boreholes, based on the analysis of the principle of pressure air drainage, the idea of introducing the accumulated water in boreholes into the vertical well and then centralized drainage once again is explored. The centralized drainage technology of large-borehole vertical wells is innovatively proposed, the principle and technology of centralized drainage of vertical wells are expounded, and the minimum drainage pressure of vertical wells is determined. The experimental investigation of 1161(1) roof roadway test unit shows that after 15 days of centralized drainage of large-diameter vertical shaft, the water level in downward boreholes drops below the coal seam floor, the gas extraction channel is open, the average gas extraction concentration of low permeability thin seam test unit is increased to 17.6%, the average 100 holes extraction purity is 0.13 m³/min, and the high-efficiency extraction time lasts for more than 70 days, and the unit evaluation is carried out. The time was shortened by 3.2 times.