An annular groove is formed in {HEAD ~ the bore} of {TAIL ~ the wellhead housing} above the casing hanger 
An annular groove is formed in { HEAD ~ the bore } of { TAIL ~ the wellhead housing } above the casing hanger
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH