Enhanced oil recovery process using a hydrophobic associative composition containing a hydrophilic/hydrophobic polymer

An enhanced oil recovery process which comprises forcing an aqueous flooding medium from an injection well through a subterranean formation toward a producing well wherein the flooding medium contains (1) a mobility control agent which is soluble in an aqueous flooding medium, said agent comprising a hydrophilic/hydrophobic polymer having hydrophobic moieties and a water-dispersible, non-ionic surfactant having hydrophobic groups that are capable of associating with the hydrophobic moieties of the polymer wherein the proportion of the polymer and the surfactant is such that, at ambient conditions, water containing 0.5 weight percent of the agent has a viscosity at least twice the viscosity of water, said agent having been prepared by carrying out the polymerization to form the polymer in the presence of the nonionic surfactant, the ratio of the surfactant to the polymer in said agent being sufficient to provide a viscosity at least twice that of an aqueous solution containing only the polymer and (2) a water-soluble, non-polymeric electrolyte which can reduce the critical micelle concentraion of the surfactant when the electrolyte is added to an aqueous solution of the surfactant, said hydrophilic/hydrophobic polymer being (a) a copolymer of from about 40 to about 99.9 mole percent of acrylamide, from 0 to about 50 mole percent of acrylic acid, and from about 0.1 to about 10 mole percent of an alkyl methacrylate or acrylate wherein alkyl has from 8 to 12 carbon atoms or an ar-alkyl styrene wherein alkyl has from 4 to 8 carbons and (b) having a weight average molecular weight in the range from about 800,000 to about 3 million and said surfactant being an alkyl polyethyleneoxy glycol monoether wherein alkyl has from 8 to 20 carbon atoms and there are from 1 to 12 ethyleneoxy groups per molecule of surfactant.