Abstract: The invention relates to an internal olefin sulfonate composition, which comprises an internal olefin sulfonate and a second surfactant which is selected from the group consisting of: (1) a compound of the formula (I) R—O—[R?—O]x—X wherein R is a hydrocarbyl group, R?—O is an alkylene oxide group, x is the number of alkylene oxide groups R?—O, and X is selected from the group consisting of: (i) a hydrogen atom; (ii) a group comprising a carboxylate moiety; and (iii) a group comprising a sulfonate moiety; (2) an alpha olefin sulfonate; and (3) an alkyl aromatic sulfonate; and wherein the weight ratio of the second surfactant to the internal olefin sulfonate is below 1:1. Further, the invention relates to a method of treating a hydrocarbon containing formation wherein said internal olefin sulfonate composition is used.

Abstract: The invention relates to a method of treating a hydrocarbon containing formation wherein an internal olefin sulfonate composition is used, which comprises an internal olefin sulfonate and a second surfactant which is selected from the group consisting of: (1) a compound of the formula (I) R—O—[R?—O]x—X wherein R is a hydrocarbyl group, R?—O is an alkylene oxide group, x is the number of alkylene oxide groups R?—O, and X is selected from the group consisting of: (i) a hydrogen atom; (ii) a group comprising a carboxylate moiety; and (iii) a group comprising a sulfonate moiety; (2) an alpha olefin sulfonate; and (3) an alkyl aromatic sulfonate.