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通过数值分析和现场试验的手段分析了井下低透气性煤层分段点式水力压裂的原理和过程.井下分段水力压裂意在改变传统压裂的受力方式,使煤体多点受力,相互作用,最后产生压裂的效果.经过在城山煤矿西二采区水力压裂孔的试验,在压裂半径为5～7m条件下,得出了试验地点临界注水压力为14MPa,水压在14～20MPa进行分段点式水力压裂较为适宜,试验过程简单易行,在现有条件下压裂可在5 min内完成,试验地点压裂后钻孔平均抽放瓦斯流量和体积分数明显提高.
Through numerical analysis and field test, the principle and process of sub-point hydraulic fracturing in low-permeability underground coal seam are analyzed.The hydraulic fracturing in sub-surface section intends to change the stress mode of traditional fracturing, After the test of hydraulic fracturing hole in the second mining area of Chengshan Coal Mine, under the condition of fracturing radius of 5 ~ 7m, the critical injection pressure of the test site is 14MPa, the water Pressure fracturing at 14 ~ 20MPa is more suitable for sub-point hydraulic fracturing, the test process is simple and easy, under the existing conditions fracturing can be completed within 5 min, the average drainage gas flow rate and volume Score significantly improved.