Effect analysis on fracturing of coalbed methane surface well and long distance borehole gas drainage technology in underground mine

According to the problem of single surface well or a borehole in underground mine applied to drain the gas was irational in effect,the paper proposed that w hile the fracturing and permeability improvement conducted in the coalbed methane surface well,in combination with the gas pre-drainage technology with long distance bor eholes set for the pressure releasing and permeabllity improvement in a local scope,thus the seam permeability was doubly improved and a considerable drainage effect W as realized. The micro seismic,underground mine observation method and other crack manual monitoring and measuring technology were applied to evaluate the crack for m and effective radial of the surface well fracturing.The gas content of the test zone,gas flow of 100 m borehole,gas drainage quantity,gas concentration,outburst danger in dex and other related parameters were investigated.The results showed that the influence scope of the surface well fracturing was in an elliptic interval,a major semi-axis W as 70 ~ 100 m generally,minor semi-axis was 20 ~ 30 m and the crack form was vertical crack mainly. The gas drainage value and concentration from the fracturing affected zone were obviously improved.After the fracturing conducted,the percentage of the high outburst prevention index was highly reduced,but the fracturing effect would be ste adily reduced with the time passed.