The large temperature gradients experienced by crude oil emulsions in pipelines found in colder environments can lead to the precipitation, deposition and build-up of wax-like species from the crude oil onto the pipe wall that result in flow assurance problems. The objective of this thesis was to understand the rheological behaviour of model water-in-oil emulsions stabilized by wax crystals. The microstructure, phase transitions and rheology of model emulsions constisting of water, mineral oil, parrafin wax and the emulsifier polyglycerol polyricinoleate (PgPr) were investigated. Changes in emulsion flow begaviour (steady state and dynamic) as a function of composition, termperature and passage through a laboratory-scale flowloop were investigated, with these parameters significantly affecting shear flow, yield stress and viscoelasticity. The gelation temperature of wax-containing ('waxy') oil was slightly lower than that of its equivalent emulsion due to differences in the structure of the gelled emulsion network. Overall, this study successfully showed that there exist significant differences in the microstructure and flow behaviour of model crude oil emulsions when wax and a dispersed aqueous phase are present.
The Formation of the Structure of Water-Oil Emulsions
