Performance evaluation and application of the surfactant combinations showing ultra-low oil-water interfacial tensions

In order to select a surfactant formulation with an ultra-low oilwater interfacial tension for application in a low permeability oil field, surfactant combinations were developed consisting of non-ionic alkanolamides, anionic alkyl benzene sulfonate and betaine in certain proportions. The results showed that the oilwater interfacial tension (oil from the Changing Jing'an field) could decease to 10 mN m∼10 mN m in the wide surfactant concentration range of 0.3%∼0.6% and a salinity of 100000 mg L at 408C∼70 8C. From 2012 to 2013, the field tests of 8 injection and 39 production wells were carried out. The water-cut escalating rate decreased from + 1.26% to-0.15 % monthly. The yield changing rate increased from-1.59% monthly to + 0.12%. The valid period of the test was more than 10 months. The improved oil recovery of the in-test well groups were predicted to increase 6.3% using type A characteristic curve of drive water. When comparing the three injection technologies, the key to the success of field application of surfactant combinations having an ultra-low oil-to-water interfacial tension is a consistent profile protocol of water injection.