Conoco Inc.

Continental Oil Company

M Duane Gregory

Charles R Clark

Carl D Kennedy

Oliver C Kerfoot

Delmar D Krehbiel

In cosurfactant enhanced alkaline flooding of a formation containing anhydrite, the pH of the flooding material is maintained at a high lvel by the addition of an alkali metal sulfate or ammonium sulfate.

Cosurfactant enhanced alkaline flooding in an anhydrite formation

An improved anionic waterflood additive is prepared by partially chlorinating a normal alkane having about 10 to about 18 carbon atoms to about 2 to about 15 weight percent chlorine content, employing the chlorinated alkane to alkylate an aromatic hydrocarbon, such as benzene; sulfonating the thus formed alkylate or a fraction thereof to form a sulfonic acid; converting the sulfonic acid to a sulfonate by reacting with a base component, such as an alkali metal hydroxide, ammonium hydroxide, or an alkali metal carbonate; and overbasing the sulfonate by admixing with an excess of base component such that the ratio: 'weight of excess base component/weight of sulfonate' is about 0.03 to about 3.0. The anionic waterflood additive is injected into a petroliferous formation, the formation is waterflooded, and oil is recovered.

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Ponca City, OK, United States of America

M Duane Gregory