After water and a significant amount of methane is recovered from the coal bed, an inert gas such as {HEAD ~ nitrogen} is injected into {TAIL ~ the coal bed formation} 
After water and a significant amount of methane is recovered from the coal bed , an inert gas such as { HEAD ~ nitrogen } is injected into { TAIL ~ the coal bed formation }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL