In crude oil extraction, the multiphase fluid formed by oil, natural gas and a large amount of brine is subjected to strong shear at the perforation layer, downhole pump and wellhead, resulting in aggravated emulsification. Natural emulsifiers and solid impurities in crude oil further stabilize the emulsification interface, making it difficult to separate the emulsion. Most of the crude oil initially extracted is oil-in-water emulsion, which needs to be converted into a water continuous phase to achieve effective oil-water separation. However, gravity separation efficiency is low, especially when the relative density difference between hydrocarbons and water is small. In order to improve the demulsification effect, natural gas in the fluid is often removed first, which can be achieved by heating oil or emulsion, which can not only promote static coagulation of emulsion, but also melt wax, reduce crude oil viscosity, and make water droplets easy to settle. The most commonly used method is to add chemical demulsifiers, which are injected from the wellhead and mixed with the fluid to reach the emulsification interface, and adsorbed to the emulsifier through polarity differences, neutralizing the emulsification, making the water droplets merge and increase, and achieving separation. In addition, demulsifiers are also used for desalting in refineries. Imported crude oil contains 1% water, which dissolves a large amount of salt and damages the catalyst. Fresh water is added and demulsifier is used to condense salt. Under the action of electrostatic grid and desalting demulsifier, condensation and dehydration are achieved to produce crude oil suitable for refining.
