Layer-penetrating staged fracturing law of horizontal wells within roof of coal seams under stress interference

Layer-penetrating fracturing is the key link to improve production in horizontal well within roof, and stress interference has important influence on layer-penetrating segmental fracturing effect in the horizontal well within roof. Therefore, the layer-penetrating segmental fracturing numerical model of horizontal well within roof is set up, the influence law of fracture propagation on stress interference to layer-penetrating segmental fracturing is studied. The results show that:the rock mechanics parameters, the interval distance and the fracturing construction method are the three important factors affecting the intersegment disturbance of the horizontal well within roof. As the Poisson's ratio of the coal seam goes down, the superposition horizontal stress increases gradually and the intersegment disturbance degree increases. With the increase of the interval distance, the superimposed horizontal stress gradually decreases and the stress interference gradually weakens. The superposition stress in roof strata is obviously greater than that in coal seam, and the interference degree of stress in roof strata is stronger than that in coal seam. The superposition horizontal stress produced by seepage diffusion pressure relief fracturing is obviously lower than that of continuous fracturing, and the interference degree between sections is obviously reduced. The results show that it is reasonable to keep the interval about 90 m in the medium hard coal seam under continuous construction, the interval of soft coal seam is reasonable about 70~80 m. The interval by seepage diffusion pressure relief fracturing is reduced correspondingly, and the interval between the medium hard coal seams is reasonable at about 70 m. The interval of soft coal seam is reasonable about 60 m. The engineering practice shows that the fractures of fracturing penetrate the coal seam and form relatively longer fractures in horizontal well within roof, thus achieving better gas production effect and achieving the goal of efficient layer-penetrating segmental fracturing for horizontal well within roof. The research results provide theoretical basis for the research on segmental interval optimization of horizontal well within roof.