Wellbore WB contains a conventional drill pipe DP extending from the surface S to {HEAD ~ the lower end} of {TAIL ~ the wellbore} 
of
Wellbore WB contains a conventional drill pipe DP extending from the surface S to { HEAD ~ the lower end } of { TAIL ~ the wellbore }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL