Coal Engineering ›› 2025, Vol. 57 ›› Issue (9): 109-116.doi: 10. 11799/ ce202509015

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Comprehensive technology of roof cutting roadway protection and gas extraction based on directional drilling and staged fracturing

  

  • Received:2025-07-01 Revised:2025-08-17 Online:2025-09-10 Published:2025-10-13

Abstract:

Aiming at the serious deformation of the wall of the gob-retaining lane along the roof of the composite key layer of the protruding coal seam, the difficulty in support, and the large amount of gas leakage in the gob, the theoretical modeling and mechanical analysis were used to study the effective pressure relief and stress transfer when the segmented fracturing fracture line was located outside the wall of the gob in the 20107 working face of the Qincheng Coal Mine in Shanxi Province. The analytical solution of the horizontal distance of the starting point of the segmented fracturing was given, and the positions of the middle and low bearing key layers were determined by combining the key layer theoretical analysis. The horizontal distance of the starting point of the segmented fracturing was determined to be 8.6m, and the vertical fracturing interval was determined to be 6.1-21.8m (low position) and 24.1-42m (middle position) from the roof. At the same time, it was pointed out that the triangular area between the fault line and the natural collapse line of the overburden is the gas enrichment area of the gob, and then the drilling layer of the gas extraction in the fracture zone was optimized to be 32-50m. The non-permeability fracturing theory and field tests of geostress were used to obtain the initiation and expansion pressures of staged fracturing of 26 and 20 MPa, respectively. The fracturing time was then determined to be 20 minutes and the flow rate was 22 m3/h, which ultimately formed an integrated technology of staged fracturing, cutting and protecting the roadway and gas extraction in the composite key layer of the high-burst mine. The field engineering test verified that the horizontal and vertical deformations of the optimized roadway wall were reduced by 1.41 and 1.82 times respectively compared with the original ones, and the gas extraction volume of a single hole in the directional drilling site increased by 0.72 times, and the total volume of each group was increased to 7.46 m3/min, achieving the coordinated governance of the deformation and instability of the roadway wall and the gas in the goaf.

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