Abstract: A process for the recovery of oil from subterranean oil reservoirs by waterflooding employing ether-linked sulfonate surfactants in which oxidative degradation of the surfactant is retarded through the establishment of an anaerobic condition in the surfactant solution or through the use of oxidation inhibitors. The anaerobic condition may be provided by mechanical means such as scrubbing the injected water with an inert gas in order to remove oxygen or by employing produced well water which is handled under a closed system to exclude oxygen. A preferred class of oxidation inhibitors are sterically hindered phenolic compounds which function as free radical chain inhibitors.

Abstract: Waterflood process for the recovery of oil from a subterranean oil reservoir in which at least a portion of the injected water is thickened by the addition of a surface-active amphoteric quaternary ammonium sulfonate and an aliphatic alcohol containing from 5 to 8 carbon atoms. The alcohol is employed in a concentration to provide a ratio of the volume amount of alcohol in the solution to the weight amount of the amphoteric sulfonate within the range of 0.1-0.6 to produce a pronounced thickening effect. The alcohol-amphoteric sulfonate systems are useful viscosifiers in highly saline systems.