injecting into {HEAD ~ the formation} through {TAIL ~ an injection} well about 0.05 to about 1.0 pore volumes of an aqueous surfactant slug comprising about 0.1% to about 10% by weight surfactant system 
through
injecting into { HEAD ~ the formation } through { TAIL ~ an injection } well about 0.05 to about 1.0 pore volumes of an aqueous surfactant slug comprising about 0.1 % to about 10 % by weight surfactant system
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH