Abstract: Drop volume method was used to measure the dynamic interfacial tension at the crude oil/brine interface. Experiments were performed with the existence of a nonionic demulsifier in water or crude oil under different concentrations and at three operation temperatures.
The result shows that (1) natural surfactants in crude oil were adsorbed slowly to the interface; (2) the fast build -up of demulsifiers present in crude oil at the interface was observed and they had advantage in the competition; (3) the concentration and operation temperature of demulsifier played an important role in affecting the dynamic interfacial tension data. Our investigation shows the ways to optimize the demulsification conditions and understand the demulsification mechanism.

Key words: demulsifier, dynamic interfacial tension