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