METHOD FOR ENHANCING THE RECOVERY OF PETROLEUM FROM AN OIL-BEARING FORMATION USING A MIXTURE INCLUDING ANIONIC AND CATIONIC SURFACTANTS

摘要

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.