Synergistic effect of demulsifiers with different structures for crude oil emulsions

In practice, synergetic effect of the interaction between different demulsifiers is often sought for dewatering the water in oil emulsion of crude oil. Surface tension, interfacial tension, interfacial shear rheology and demulsification test was employed to study the synergistic effect of demulsifiers with different molecular structures, one is the strait-chain demulsifier SP31 and the other branch-chain demulsifier AE31. The strait-chain demulsifier SP31 has a lower IFT but a longer balance time compared with the branch-chain demulsifier AE31. The dewatering rate of AE31 is faster than that of SP31 but the separated water after demulsification for 1 h by SP31 is clearer. It is mainly because the branch-chain demulsifier has stronger penetrability at oil/water interface. When the percentage of SP31 is 40～60%, the complex demulsifier of SP31 and AE31 exhibits the synergistic effect of demulsification performance due to the instantaneous relatively low interfacial tension and the strongest capacity to decrease the strength of the oil-water interfacial film.