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