Effects of crude oil characteristics on foaming and defoaming behavior at separator during CO2 flooding

Abstract

CO2 flooding effectively enhances the recovery of crude oil. However, a large amount of foam is generated in the separator when the produced oil releases gas due to depressurization, which reduces the separator capacity. To address the foaming problem, this paper provides some qualitative and quantitative insights by studying the effects of depressurization, resin, asphaltene, wax crystal and other factors on the foaming and defoaming characteristics of four crude oils. A set of experimental devices is developed to assess foaming during depressurization. The experimental results indicate that a larger pressure drop increases the amount of foam generated and the defoaming rate. The ratio of resin to asphaltene is closely related to the foaming and defoaming characteristics of crude oil, and the effect of asphaltene on foam stabilization is greater than that of resin. There is a threshold wax crystal content for affecting the foaming and defoaming characteristics of crude oil. A small amount of wax crystals accelerates foam bursting, but further increasing the wax crystal content stabilizes the foam. These results provide guidance and a reference for CO2 flooding technology, the improvement of separators and research on the foaming and defoaming mechanisms of crude oil.