reacting the oxidant and {HEAD ~ fuel} in {TAIL ~ the oxidizers} to produce heat to heat a portion of the formation; and 
in
reacting the oxidant and { HEAD ~ fuel } in { TAIL ~ the oxidizers } to produce heat to heat a portion of the formation ; and
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH