Abstract: Lithium salts are employed as sacrificial agents for use in surfactant flooding operations within subterranean petroleum reservoirs. They can be utilized within a preflush treatment and/or by incorporation within the surfactant slugs injected into the petroleum formation.

Abstract: A process for recovering hydrocarbons from a hydrocarbon-bearing formation penetrated by an injection well and a production well which comprises injecting an aqueous solution of a vinylpyrrolidone polymer into the formation to condition the reservoir, in a first step injecting an aqueous surfactant solution into the formation and recovering hydrocarbons via the said production well. The pretreatment of the formation with the vinylpyrrolidone polymer reduces the consumption or loss of surfactant and thus improves the efficiency of the process. Optionally, after the injection of the aqueous surfactant solution an aqueous drive fluid is injected into the formation.