Abstract: An improved method for the recovery of tertiary oil from oil formations containing connate waters having a high brine concentration. A stable alcohol external microemulsion is formed from specific brine-soluble surfactants and alcohols for employment as a chemical slug. Such a microemulsion may be used to efficiently and effectively recover tertiary oil from formations in high brine concentrations. Specific examples of surfactants which may be employed to form the microemulsions of the present invention include amphoteric surfactants such as bis-2-hydroxyethylcocoamine propane sulfonate and bis-2-hydroxyethyloctadecyl amine propane sulfonate.

Abstract: Waterflood oil recovery process involving the use of an amphoteric polyelectrolyte as a thickening agent for mobility control. The amphoteric polyelectrolyte is a copolymer of a quaternary vinyl pyridinium sulfonate and a water-insoluble alpha olefin or hydrogenated diene. Specifically disclosed are vinyl pyridinium sulfonate-styrene block copolymers. The amphoteric polyelectrolytes are stable in high temperature and high brine environments.