At least one common well is used for {TAIL ~ recovery} of methane from the formation and introduction of {HEAD ~ hydrogen} into the formation 
At least one common well is used for { TAIL ~ recovery } of methane from the formation and introduction of { HEAD ~ hydrogen } into the formation
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH