Variations in coalbed gas content, initial gas desorption property and coal strength after drilling-slotting integration technique and gas drainage: insight into pore characteristics

摘要

In this paper, the variations in coalbed gas content, initial gas desorption property and coal strength after drilling-slotting integration technique and gas drainage were investigated by testing seven coal samples obtained from the coal seam #10 of Yangliu Coal Mine. The MICP and N2GA were combined to characterise the pore-size distribution. It is revealed that the residual coalbed gas content decreases substantially with the decrease in boreholes distances. Nevertheless, the variations in initial gas desorption velocity and coal hardiness coefficient represent an opposite tendency. In the microscopic aspect, the variation in pore-size distribution is notable. With the decrease in the boreholes distances, the adsorption pore proportion decreases and the seepage pore proportion increases. The drilling-slotting integration technique and gas drainage affect the aforementioned three macroscopic indices by changing the pore characteristics and moisture content. Besides, the guiding significance for field application of this technique is elaborated.