Application of permecbility improvment technology with liquid Co_2 phase transition fracturing to high gassy and low permeability seam

According to the high gasy low permeablity status of the seam in No.13 M.ine of Pingdingshan Tian an Coal Company and in orer to improve the gas drainage volume of the mine,the liquid Co _2 phase ransitin fracturing techinology was apled to the enmhanced gas drainage.The experimen stcdy was conduced on he permeabilityimproved mechanism and the outburst elinination and pemeability improved efiect of the licuid co 2 phase rnstion fracturing echmogy in the highgassy and low permeability sean. Wirth the liquid co _2 phasetrnstin fracturing technology appid to the foor drainagegateway of th Ji15.17-1111 tansportationroadwaythe special licuid cO_2 phase ransition fracturing device appied could make a frcturing explosion during the bed crossing borehole,could make the cracks around the coal mass could make the permeability coicient increased of the seam.The experinent resut howed thathe average drainage concentration fom a singlegas borehole was 1.42 times igherthan betore the experiment. A daly average drainage pure volume from a single gas borehole was 2.17 times higher than before the experinent.The attenuation period of the gas drainage was expanded over two times at least and the pre-drainage effect of the seam gas could be effectiv ly improed.