| Summary: | In recent years, most of the mature oilfields in the world have needed enhanced oil recovery (EOR) techniques to maintain their production level. Nevertheless, each EOR technique suffers from a number of limitations. Surfactant flooding, which is a conventional EOR method, can cause emulsification and displacement of the trapped oil in the reservoir. Surfactants are the most expensive components in a microemulsion. Therefore, selecting a proper surfactant formulation which can mobilize oil without considerable surfactant adsorption is very important. The application of ultrasound is one of the unconventional EOR methods. This causes emulsification of oil and water in the reservoir. Integration of surfactant flooding and ultrasound has the potential to decrease surfactant consumption. Therefore, in the case of integrated ultrasound-surfactant flooding, the phase behavior of surfactant-brine-oil, herewith referred to as the SBO system, is crucial and needs to be investigated. In this study, the effect of ultrasonic stimulation duration on the phase behavior of an SBO system was investigated, and changes in solubilization parameters and optimal salinities are discussed. By comparing the results of the phase behavior of SBO under short and long durations of ultrasonic stimulation, it was concluded that a short duration of stimulation (15. min) yields more volume of microemulsion compared to cases using no ultrasound and a longer duration of ultrasound stimulation. Therefore, by using short durations of ultrasonic stimulation in the integrated ultrasound-surfactant flooding process, the interfacial tension remains low and the surfactant consumption decreases. © 2015 Elsevier B.V.
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