Microscopic mechanism for enhanced coal bed methane recovery and outburst elimination by hydraulic slotting: A case study in Yangliu mine, China

Coal bed methane (CBM) is a clean, efficient, and environmentally friendly energy, and its efficient exploitation can meet the growing demand for energy worldwide. Besides, methane (CH4) is a greenhouse gas (GHG) and is 25-72 times more powerful than carbon dioxide (CO2) in inducing global warming. With regard to the mining industry, CBM is regarded as a major hazard resource, as its inadequate management or control may lead to serious coalmine accidents. In China, gas drainage is the main measure adopted to resolve this problem. However, because the coal seams in China are characterized by low permeability, it is difficult to drain the gas contained in coal mass. Therefore, measures must be taken to reconstruct the coal reservoir to enhance coal seam permeability. In China, hydraulic slotting has been widely accepted and applied in coal mine engineering owing to its permeability-enhancement effect. In this work, based on our previous research, we systematically elaborate the mechanisms of permeability enhancement and elimination of coal and gas outburst by hydraulic slotting from microscopic perspectives. To examine the rationality and practicability of the research results and the permeability-enhancement effect of hydraulic slotting, a field experiment was conducted and the monitoring results were analyzed. Our results show that the gas flow rate and concentration in the slotted boreholes are significantly higher than those in the conventional boreholes. In addition, the time required by the slotted borehole to eliminate the outburst is 72.41% less than that needed by the conventional borehole. The practice in Yangliu coalmine could be extended to other coal mines with similar reservoir conditions. (c) 2016 Society of Chemical Industry and John Wiley & Sons, Ltd