Mining Publication: Degasification Study From an Air Shaft in the Beckley Coalbed

The Bureau of Mines conducted research to degasify a virgin block of coal in the Beckley coalbed using long horizontal holes drilled in an array from the bottom of a ventilation air shaft. Eight horizontal holes and an in situ pressure hole were drilled in a radial pattern to depths ranging from 418 to 910 ft (127 to 277 m) and 205 ft (62 m), respectively. The investigation showed the shaft was in a basin saturated with water, which resulted in low gas flows from holes. The in situ pressure at 200 ft (61 m) into the coalbed was 79 psig (544.6 Kn/m2). The average gas and water flows for the eight holes were 94,100 ft3/day (2,665 m3/day) and 13 gal/min (49.3 L/min). After 514 days of degasification, 18.7 million ft3 (0.53 million m3) of gas had been drained. Methane face emissions, which were measured as a section advanced toward the shaft, were reduced about 77 pct, emphasizing the value of drainage by this technique. All holes were grouted before the area around the shaft was mined.