said oil removal means comprises an oil outlet opening to said oil recovery zone at said {HEAD ~ intermediate level} of {TAIL ~ the latter zone} 
of
said oil removal means comprises an oil outlet opening to said oil recovery zone at said { HEAD ~ intermediate level } of { TAIL ~ the latter zone }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL