The use of coal cuttings from underground boreholes to determine gas content of coal with direct desorption method

In underground coal mining operations, gas content in a coal seam is used to assess the risk of coal and gas outbursts. A broadly standard procedure has been adopted to estimate the gas content with coal core in the coal mining industry. In soft or friable or geologically complex sections of coal seams, it has proven to be extremely troublesome in taking coal cores as cores can be severely fragmented or sometimes it is simply impossible to core with conventional coring methods due to poor borehole stability, leaving coal cuttings from boreholes as the only practical alternative for sampling. When coal core is replaced with coal cuttings, concerns have been raised about the validity and accuracy of the procedure used for gas content determination with coal core, in particular with respect to the sampling method of coal cuttings and gas content calculation due to faster initial gas desorption rates of coal cuttings. The standard procedure for gas content determination with coal core has been modified to determine gas content of coal with coal cuttings from underground boreholes. This paper describes the modified method and presents and discusses the results when it was trialed in a soft coal seam at Huainan, China.