Application of Directional Long Borehole Regional Fracturing Technology in Deeply Buried Coal Seam Roof Pressure Relief
In order to effectively unload the pressure on the roof of the deep working face and avoid the enormous impact load caused by roof pressing during mining,reducing the risk of impact,it is necessary to address the issue of the limited effectiveness of hydraulic fracturing in the shallow hole due to depth and borehole angle restrictions in the overlying strata area of the entire mining face.Taking the ZF1407 working face of Yadian coal mine as the background,the directional long borehole hydraulic fracturing technology is employed to pre-fracture the roof,altering the stress state and energy accumulation degree of the surrounding rock in the deep area to achieve controlled deformation of the roadway and efficient pressure relief.Research results indicate significant changes in the distribution of internal fractures in the fractured formation before and after fracturing,with a large number of fractures generated in the fractured layers.The distribution of microseismic events is concentrated towards the working face,reducing the advance distance of the working face by 80%,and the average daily total energy of microseismic events decreased by 63.3%,while the average daily total frequency of microseismic events decreased by 72.5%.The long borehole hydraulic fracturing technology in the thick and hard rock formation provides fracture control,reduces the step distance of fracturing and the intensity of energy release in the thick and hard rock formation,which helps alleviate the impact of fracture instability in the thick and hard rock formation on the underlying mining space,resulting in a significant pressure relief effect.
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