A method for improving the methane extraction concentrations of in-seam boreholes

The methane extraction concentrations of in-seam boreholes are generally attenuated at a relatively fast rate in the majority of China's coal mines, which seriously restricts the efficiency of methane extractions in underground coal mines. The rapid decrease in methane extraction concentration is mainly due to air leakages of the in-seam boreholes. In the present study, the air leakages mechanism of in-seam boreholes was analyzed. Then, based on the mechanism of air leakages, a method for increasing methane extraction concentrations of the in-seam boreholes was proposed. Moreover, the key equipment related to this proposed method was successfully developed, and the specific processes of this method were described in detail. Finally, the proposed method was applied in Chinas Guozhuang Coal Mine. It was found that the field test results indicated that after using the newly introduced method, the average methane extraction concentration of the in-seam boreholes had exceeded 30%, which was higher than methane concentrations in the boreholes when the previous method was adopted. Furthermore, when compared with the previous method, the effective extraction life of the borehole using the new method introduced in this study was extended by more than 2.1 times.