Method of treating a hydrocarbon containing formation

Abstract

The invention relates to a method of treating a hydrocarbon containing formation, comprising: a) providing an aqueous composition which comprises i) an internal olefin sulfonate (IOS) surfactant; ii) an acid which has a pKa between 4 and 12; and iii) the conjugate base of the acid mentioned under ii), to at least a portion of the hydrocarbon containing formation, by combining the aqueous composition with a hydrocarbon removal fluid to produce an injectable fluid, wherein the hydrocarbon removal fluid comprises 1) water and 2) divalent cations in a concentration of 50 or more parts per million by weight (ppmw), and injecting the injectable fluid into the hydrocarbon containing formation; and b) allowing the surfactant from the injectable fluid to interact with the hydrocarbons in the hydrocarbon containing formation.

Dependencies are inferred from the claim text.