The formation of water in crude oil emulsions in oil production systems can cause a significant reduction of the production rates. The effective viscosity of the emulsions increases with the amount of the dispersed water. The accurate prediction of the effective viscosity is of importance for the appropriate design of the production systems. Current practices to measure and predict the effective viscosities involve the use of rheometers and small scale loops. However, some questions remain about the applicability of this small scale results for large scale real systems. The objective of this work is to study the influence of the pipe diameter on the flow of water-in-oil emulsions. Pipe flow experiments were carried out with water-in-oil surfactant stabilized emulsions. 0.25% in volume of a lipophilic surfactant (Span 80) in oil Marcol 52 (μ=10 mPa.s) and salt water (3.5% in weight) were used. Pressure drop measurements at different water cuts in acrylic pipes with 60 and 90 mm of internal diameter (ID) were performed. Results show that at the tested water cuts significantly higher effective viscosities result in the larger pipe diameter for similar shear rate conditions. This difference was observed to increase with water cut. In addition, a non-Newtonian behaviour of the emulsion was observed at high water cuts. This was verified by measuring the velocity profile using a Pitot tube. In-situ droplet sizes were measured using the focused beam reflectance technique. Neither the droplet size distribution nor the velocity profiles seem to be the reason for such a difference in the effective viscosity. The distribution of the dispersed water phase across the pipe section was measured using a traversing gamma densitometer.
The formation of water-in-oil dispersions is commonly found in different stages of oil production systems.