This paper describes some simple correlations which can be used to obtain reasonable estimates of relative viscosities and viscosities of water-in-crude oil emulsions.

The apparent viscosities of water-in-crude oil emulsions based on eight different North Sea crude oils of different types have been fitted to a general empirical equation which provides estimates of relative viscosities at temperatures between 5 and 40°C, water cuts between 10 and 60% and shear rates between 30 and 500 s‒1. The estimates are in general within 15-30% of experimental values. A correlation between crude oil viscosity and average molecular weight, can be utilized to obtain estimates of emulsion viscosities above about 20 °C, when only the molecular weight of the crude is known.

The yielding (or restart) behaviour of some of the emulsions at low temperature (5 °C) is described in terms of static yield stress as a function of water volume fraction.

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