Permeability improvements of an outburst‐prone coal seam by means of presplitting and blasting with multiple deep boreholes

Abstract

Abstract Coalbed methane, which is a significant potential unconventional source of energy, exhibits considerable challenges in the implementation of the exploration and production process, especially the degasification in low permeability of coal seams with high gas concentrations. Due to the difficulties in gas extraction, long mining period and low extraction concentration in soft and outburst coal seams, the permeability improvement method using presplitting and blasting technology with multiple boreholes has been proposed and applied to improve the permeability of soft coal seam, which is achieved by optimizing the inseam distribution of generated fractures through multiple control boreholes. Research results showed that the permeability improved by presplitting and blasting with deep boreholes is 2.5 times higher than that of the original coal seam. Within 6 days of extraction, the average extraction concentration and pure volume of the extraction borehole were 40.13% and 0.113 m3/min, respectively, which are 2.9 times and 4.1 times higher than the original data, respectively. Likewise, the average extraction concentration and purity of the extraction hole were 21.75% and 0.063 m3/min after being extracted within 14 days, which is twice and three times higher than that of the original average extraction concentration and purity volume, respectively. Besides, proposed technology has a little influence on the methane concentration of the coal seam 70 m ahead of the heading face. The research results promote the prevention and control of coal‐gas outburst in low permeability and high gas concentration coal seams.

Keywords

• methane extraction
• multiple deep boreholes
• outburst coal seam
• permeability improvement
• presplitting and blasting