Study on antireflection technology of multi-component acid fracturing in low permeability coal seam

In order to solve the problem of poor permeability of coal seam rich in carbonate minerals, the antireflection technology of multi-component acid fracturing was proposed.Through the laboratory test of permeability changes of coal samples before and after acidizing, the acid ratio suitable for Sanyuan Coal Mine was w(HCl)=9%+w(CH₃COOH)=3%+ρ(KCl)=20 g/L. The field industrial test results show that:after the multi-component acid fracturing is adopted in Sanyuan Coal Mine, the mixed flow and concentration of the gas drainage are increased by 1.34 times and 1.70 times respectively on average compared with that of the ordinary drilling. Compared with the traditional antireflection technology of hydraulic fracturing, through the combination of physical and chemical antireflection, multi-component acid fracturing is more conducive to the development of pore fracture network structure of coal mass, and the carbon dioxide produced by reaction has a displacement effect on gas, which is conducive to gas drainage; at the same time, expanding the drilling diameter can effectively improve the area of high-pressure fracture contact surface and drainage free surface, and further improve the effect of antireflection drainage.