The influence of asphaltene and resin on the stability of crude oil emulsion and its demulsification mechanism

Currently, the effects of natural emulsifiers such as resin and asphaltene in crude oil on the stabilities of the emulsions as well as the demulsification mechanism of oil-water separation are still not well understood. In this study, the changes in oil-water wetting angle and interfacial tension (IFT) of crude oil emulsions were compared by extracting resin and asphaltene from crude oil to expound the effects of resin and asphaltene on the stabilities of crude oil emulsions. Meanwhile, the mechanism of demulsifier was discussed based on the competitive adsorption test of demulsifier and asphaltene. It was found that asphaltene was the main emulsifier in the process of oil-water emulsification. With the increase of asphaltene contents, the oil-water wetting angle decreased from 72.9 degrees to 37 degrees, the IFT decreased from 27.13 mN/m to 11.23 mN/m, and the emulsion droplet decreased from 10.3 mm to 1 mm. Demulsifier mainly reduced the stability of crude oil emulsion and realized oil-water separation by the replacement of the interface film-forming substances, the reduction of the oil-water interface tension, and the neutralization of interface charges. The results provide useful information for the demulsification and oil removal of oil-bearing wastewater emulsion.