关键词: 低透煤层, 定向长钻孔, 水力压裂, 增透技术, 影响半径

Abstract: In response to reduce engineering quantity of gas drainage borehole in coal seam with low permeability, the hydraulic fracturing technology of low permeability coal seam was studied. It put forward overall hydraulic fracturing in mining-coal bed which is based on kilometer directional long hole, developed a high pressure and stable sealing equipment which is suitable for uncorrected drilling in medium-hard and low permeability coal. The hydraulic fracturing effect and influence scope were studied and evaluated by the variations comparison with the coal total moisture and borehole gas parameter during pre and post of hydraulic fracturing. The results showed that The test realized the length of the coal segment of the hole underground for the whole fracturing was up to 300 m，the injected water volume of single hole was 1613 m3， and the maximum injection pressure was up to 24.60MPa. The maximum impact radius of the fracture hole in left working slope is 33m and the right working slope is 38m. The Methane extraction from scalar increased average 12.70 times and the borehole gas drainage quantity of hectometre increased average 2.67 times which are Compared with the non fracturing data. The research results improve gas drainage rate and guarantee mine excavation replacement efficiency, provide a reference support for the whole hydraulic fracturing and highly efficient gas drainage in the similar geological conditions.