Chevron Research & Technology Company

Rawls H Frazier, Jr

William Loh

Jeremy Cantor

Donald L Kuehne

Willie Horn, Jr

A foam-forming composition comprising a mixture of at least one anionic surfactant and at least one cationic surfactant can effectively form a foam in a variety of formations including an oil-wet environment. In particular, this composition can be employed in a method which comprises at least periodically injecting a gas and this foam-forming composition into an oil-bearing formation to drive oil to a production well. In this composition, the ratio of the at least one anionic surfactant to the at least one cationic surfactant is selected so that the surfactants do not form substantial amounts of precipitate when mixed together. In certain environments, e.g., when the formation contains upwards of 20% total dissolved solids and/or a divalent metal ion concentration up to about 20,000 ppm, the composition can further contain at least one salt-tolerance additive, e.g., a nonionic surfactant.

Method for enhancing the recovery of petroleum from an oil-bearing

A method for recovering hydrocarbons from a reservoir during gas injection into the reservoir comprises at least periodically injecting a gas comprising steam and a foam-forming composition which includes at least one steam foam diversion surfactant into a reservoir which contains at least one multivalent cation. The foam forming composition comprises water, an effective foam-forming amount of the surfactant which preferably comprises an alkyl aromatic sulfonate and a precipitation control additive. This precipitation-control additive preferably comprises an alpha-olefin sulfonate dimer (AOSD). The method further comprises contacting the hydrocarbons in the resevoir with the foam and the gas so as to assist in the recovery of hydrocarbons from the reservoir.

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Richmond, CA, United States of America

Rawls H Frazier, Jr