Emulsions of Heavy Crude Oils. II. Viscous Responses and Their Influence on Emulsion Stability Measurements

Abstract

The stability of 30 heavy crude oil emulsions was studied in a parallel-plate laboratory coalescer (DC field). Particularly, viscous responses and their influence on the emulsion stability measurements were investigated. In addition to highlighting previous results from the same experimental setup and discussing these based on recent experience, new results at different temperatures and volume fractions of water were presented. A new semi-empirical model for the characteristic time of the destabilization process was presented. The electrical forces were modelled with a point-dipole approximation and the hydrodynamic resistance to droplet transport was modelled with an empirical term including the logarithmic viscosity of the oil phase. The new model clearly performed much better than the previous model, particularly for very viscous crude oils. Studies of the performance of industrial electrocoalescers have showed that simple electrostatic theory can potentially explain complex separation phenomena when the resistance to the coalescence step is reduced by an efficient demulsifier. The ultimate goal is to build a model for both the laboratory setup and the industrial coalescer so that laboratory experiments can be used to predict the behavior of the industrial process.

Keywords:

• Crude oil
• electrocoalescence
• emulsion stability
• point-dipole approximation
• temperature
• viscosity
• water cut

The authors would like to acknowledge the financial support from the participants in the Joint Industry Project, Flucha III, hosted by the Ugelstad Laboratory at the Norwegian University of Science and Technology.

Notes

^a Analytical method explained by Hannisdal et al.^{[ 22 ]}

^b Equilibrium interfacial tension and elastic modulus E'. Analytical method is explained by Hannisdal et al.^{[ 37 ]}