Abstract: The recovery of oil by surfactant waterflooding involving the injection of a hydrocarbon slug followed by a thickened aqueous surfactant slug. The hydrocarbon slug is injected into the reservoir in an amount of at least 0.02 pore volume and has a viscosity less than that of the reservoir oil. The thickened surfactant slug comprises an aqueous solution of a surfactant system which includes an organic sulfonate surfactant and which functions to increase the viscosity of the aqueous liquid to a value at least as great as the viscosity of the reservoir oil while decreasing the oil-water interfacial tension. The surfactant slug may include one or more organic sulfonates, either alone or in mixture with a water-soluble aliphatic alcohol.

Abstract: Surfactant waterflooding process involving the injection of a hydrocarbon slug followed by a surfactant slug and a mobility control slug. The hydrocarbon slug has a viscosity less than that of the reservoir oil and is injected within the range of 0.01-0.04 pore volume. The surfactant slug is injected in an amount within the range of 0.05-0.3 pore volume and exhibits a surfactant concentration within the range of 0.5-4.0 weight percent. At least a portion of the mobility control slug has a viscosity at least as great as the viscosity of the hydrocarbon slug.

Abstract: Waterflooding process for the recovery of oil in which at least a portion of the injected water is thickened by the addition of a sulfonate surfactant and a C.sub.4 -C.sub.6 aliphatic alcohol having a hydrocarbon chain link of at least 3 carbon atoms. The action of the surfactant-alcohol system in increasing the viscosity of the water varies with the monovalent salt salinity of the water and the ratio of the amount of the sulfonate surfactant to the sum of the amounts of the sulfonate surfactant and alcohol in the water. A relatively viscous aqueous mobility control slug containing a sulfonate-alcohol system as previously described may be preceded by an aqueous surfactant slug. The aqueous solution of sulfonate surfactant and alcohol may be formulated and then aged for a time to allow the development of viscosity prior to injection into the oil reservoir. This viscosity development may be accelerated by heating.

Abstract: Recovery of oil from subterranean oil reservoirs by waterflooding employing an alkaline agent and a sulfonate surfactant. An aqueous initiation slug containing an alkaline agent selected from the group consisting of alkali metal and ammonium hydroxides is injected into the reservoir via a suitable injection system. Thereafter an aqueous surfactant slug is injected into the reservoir behind the initiation slug. The surfactant slug contains a sulfonate surfactant and an alkaline agent. Subsequent to injection of the surfactant slug, an aqueous flooding medium is injected in order to displace the oil within the reservoir to a production system from which it is recovered. A portion of the flooding medium may contain a thickening agent for mobility control purposes.