Research and application of combined antireflection technology of high pressure hydraulic fracturing and punching in low permeability coal seam

Aiming at the problems of complex structural stress, low permeability coefficient and poor extraction effect in deep mining coal seam, in order to explore the optimal gas extraction technology, taking K₁ soft coal seam of Shuixi Coal Mine as the research object, four technologies including hydraulic fracturing, hydraulic punching, conventional pumping and high pressure hydraulic fracturing and punching combined antireflection were successively used to carry out the field pumping comparative application tests.The results show that: the improvement degree of permeability coefficient of coal seam by the combined antireflection technology of high pressure hydraulic fracturing and punching is 1.85 times, 1.61 times and 6.30 times of that of hydraulic fracturing, hydraulic punching and ordinary test scheme respectively, the extraction pure gas flow increases by 1.42 times, 1.33 times and 2.32 times respectively.In addition, the total gas concentration(methane volume fraction)remains above 42.6%, and the extraction efficiency is the highest among the four.The field application results show that the combined antireflection technology of high pressure hydraulic fracturing and punching has obvious technical advantages.