Research and application of directional long-borehole staged hydraulicfracturing technology for strong rock pressure in mine

In order to solve the problem that the roof of No.4-2 coal seam in Bu er tai Coal Mine of Shendong Mining Area could not collapse along with mining, resulting in large area hanging arch and strong mine pressure, the long-borehole staged hydraulic fracturing technology was introduced. It was based on directional drilling and hydraulic dual-anchor retrievable packer technology. Through industrial test of No.42107 fully-mechanized working face, the 468 m uncased hole with 9 staged fracturing for weakening roof was carried out. More than 70 times significant drop (above 3 MPa) appeared, with the max fracturing pressure up to 25.9 MPa,the lowest was 9.3 MPa. The results showed that multi-point three-dimensional fracture network was formed by directional drilling, high pressure water injection and staged fracturing on designed layer. The overhang area reduced to one seventh, with periodic weighting interval decreasing from 45 m to 25 m, realizing effective degradation of mine pressure. It provided the effective technical and equipment support for mine safety production and high efficiency.