关键词: 煤矿瓦斯, 定向长钻孔, 分段压裂, 区域增渗

Abstract: In response to the problems of small impact range, low extraction purity, and long treatment time for drilling in thick and hard coal seams, the targeted coal body is physically modified and the fracture network is transformed using the directional long drilling segmented fracturing and permeability enhancement technology along the coal seam. In response to the problems of packer damage and fracturing fluid leakage during the hard coal setting process, based on the understanding of the fracturing characteristics of hard coal and the mechanical parameter characteristics of the packer, an active pressure bearing "pressure ring internal wedge" structure improvement was carried out on its end. The thick and hard coal seam open hole setting combination tool string was selected, and after laboratory pressure testing, the sealing effect was good, meeting the requirements of multiple pressure relief and expansion. We have developed a complete set of equipment for segmented fracturing of thick and hard coal seams, as well as a reverse segmented fracturing process for directional long boreholes. Two directional long boreholes and eight fracturing tests were conducted in the No.3 coal seam of the Daning Mine in Yamei, Shanxi, with a cumulative drilling depth of 975m and a cumulative water injection of 596m3. The results showed that the gas extraction concentration in the experimental area was all above 75%. The actual impact radius of fracturing was determined by ground microseismic monitoring, transient electromagnetic in the hole, and comprehensive determination of regional seepage volume, which was 22.5-32m. The average gas extraction pure volume in DY-1 and DY-2 boreholes was 1.36m3/min and 1.22m3/min, respectively. After fracturing, the maximum and minimum gas extraction pure volume in a single borehole increased by 49% and 16%, with an average increase of about 30%. This technology has a good effect on increasing permeability in thick and hard coal seam areas, laying a foundation for the construction of advanced gas treatment systems in large regions in the future.