Demulsification of phet crude by block copolymer surfactants

The formation of petroleum emulsions during oil production is a costly problem. Petroleum emulsions have to be treated to meet crude specifications that water content must be less than 0.5% by volume. Chemical demulsification, which is the addition of minute amounts of a demulsifier (surfactant), was used in this study. The effects of water-to-oil ratio (0.5-71.3 vol%), demulsifier concentration (20-500 ppm), temperature (45-60C), and separation time (0.5-3 h) on the demulsification efficiency of different types of nonionic surfactants (EO-PO block copolymers with 6 and 17 ethylene oxides, oxoalcohol EO-PO block copolymers and ethylenediamine EO-PO block copolymers) in breaking the petroleum emulsions of Phet crude (Thailand) were investigated. Water remaining in the crude oil was determined by the Karl-Fischer method and water remaining in the emulsion was determined by mass balance. The results revealed that EO-PO block copolymers of ethylenediamine gave the best separation results. The optimum conditions are; 55C, 50 ppm of demulsifier concentration, 2-3 h separation time, and water content include of at least 40% could gave higher demulsification efficiency. D emulsification efficiency increased with increasing demulsifier concentration and temperaturel. Mixed demulsifiers showed no synergistic effect. Furthermore, large scale test gave water remaining in the crude at less than 0.5 vol% at 2 h separation time.