DOI: 10.11799/ce202509008
Staged hydraulic fracturing with directional long borehole for fully mechanized mining face in a shallow coal seam under hard roof
REN Jianxi
YAN Wei
XU Baojun
MIAO Yanping
JIAO Jinzhao
SUN Chengwei
WANG Ke
Abstract：To address the challenge of timely roof collapse during the working faces mining of shallow coal seams under hard roofs,we took on the No.517 working face of a mine in northern Shaanxi as the background,and designed a staged hydraulic fracturing scheme using directional long boreholes,and the pressure relief effect was evaluated using microseismic and field measurement data.The results indicate a significant increase in microseismic events during fracturing,along with the occurrence of high-energy microseismic events.The maximum fracturing pressure reached approximately 20.6 MPa,with a water injection rate of around 45 m3/h per fracturing section.The observed pressure drop in the fracturing curve suggests that hydraulic fracturing induces borehole fractures and a significant number of roof fractures,with the roof remaining influenced by fracturing even after construction.During mining,the stress at the base point in the shallow part of the coal pillar is significantly greater than in the deeper part.Similarly,the stress on bolts in the coal pillar side is markedly higher than on the roof and solid coal side.Meanwhile,the degree of roof strata separation remains essentially unchanged.Hydraulic fracturing effectively weakens the integrity of the hard roof,reduces lateral bearing pressure on the coal pillar,disrupts stress transmission paths,optimizes the stress environment,alleviates roadway deformation,and ensures the safe mining of the fully mechanized face.The research findings provide valuable insights for managing roof disasters in similar working faces.
Keywords：shallow coal seamhard roofhydraulic fracturingmicroseismdirectional drilling
Publication Date：2025-09-20
Online Publishing Date：2025-11-03(First online date of this platform, not the publication date of the document)
Pages：9( 49-57 )