The presence of methane gas has plagued the coal mining industry for years. Many men have lost their lives in methane-air explosions. Consequently, mining companies spend a great deal of money keeping the methane concentration at an acceptable level within the mine by diluting it with large quantities of air. Frequently, in deep, gassy mines, even the tremendous volume of air sweeping through the mine is not enough to keep machinery at the face from shutting down due to excessive methane levels. As the mine continues to advance, so do the problems as the methane content of the coal generally increases with depth. Also, with the increased number of faces, an increasing amount of gas bleeds into the mine.
One solution is to degasify the coal before it is mined. Doing so would increase safety, lower ventilation costs and, given gas ownership, can bring in additional revenue for the company. There are several methods of degasifying a coalbed prior to mining. They all consist of drilling holes into the coalbed to let the methane escape. The difference between them is the manner in which the holes are drilled and completed. Some holes are drilled from the surface and others are drilled from within the mine into virgin coal. In the case where coals are at considerable depth and under rough terrain in many western areas, horizontal boreholes from the mine workings appear to be the best method of degasification. In addition, they produce more gas per feet of hole than any other method. Horizontal holes are drilled into the coalbed, parallel to the bedding planes and away from the mine workings into virgin coal.
This report presents drilling, completion, pipe size, spacing, and recovery of methane at the Hawk’s Nest East Mine, Paonia. 19 pages. 5 figures. Digital PDF download. OF-80-07D