Dewatering of petroleum crude oil emulsions using modified Schiff base polymeric surfactants

The new discoveries of increasingly heavy oil represent a major challenge for the oil industry because of its undesirable properties, such as its tendency to form stable emulsions and high viscosity and acidity. Dependent upon the production scheme, very stable water-in-oil emulsions can be formed from these oils, for which the complete separation of oil and water phases using conventional processes requires excessive heating, chemical addition, and high residence time. In the present work, the improvement of existing technologies and the development of new additives to decrease the temperature of the treatment processes of these emulsions are very important to ensure the processing of these oils in view of productivity gains. In this respect, the rate of demulsification of different types of crude oil emulsions using series of Schiff base polyethoxylates as demulsifiers was evaluated. The chemical structure of the prepared surfactants was determined by FTIR and 1H NMR analyses. Characterization of the surface activity of the prepared surfactants is performed to investigate the relation between the structure of surfactants and their performances. The interfacial properties of the prepared demulsifiers at the oil-water interfaces were investigated by means of the interfacial tension relaxation method. The results showed that the slow relaxation processes at low concentration because of stronger adsorption ability of the prepared demulsifiers. This was attributed mainly to rearrangement in the conformation of the molecules appeared with increasing demulsifier concentration. The demulsification efficiency of the prepared demulsifiers for the synthetic crude oil emulsions was determined at different temperatures using bottle test. The demulsification rate increased with surfactant concentration up to the onset of surfactant aggregation in the oil, water phase and a third, surfactant-rich phase.