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