Experiment research on strengthening gas drainage effect with fracturing technique by liquid CO_2 phase transition

For the condition of high gas content and unsatisfactory gas pre-drainage effect in a single low permeability coal seam,the fracturing technique by liquid CO2 phase transition was adopted,and the instantaneous high pressure CO2 jet to impact the coal in the boring to produce a large number of promoted and expanded fracture was utilized in a coal seam,so as to make the permeability developed eventually.Through the experiment in 16051 floor roadway of Jiulishan Mine,it showed that the effect of gas drainage was improved obviously by the fracturing technique with liquid CO2 phase transition.The average gas flow turned to be 0.057 m3/min after experiment,which was 4.3 times of the flow before fracturing measures,and was 2.3 times of the flow by using the hydraulic flushing.The gas concentration also had been enhanced.During the test,the flow attenuation coefficient decreased to 0.046 d-1.The research results indicated that anti-reflection effect is remarkable.