ABSTRACT

A pipe viscometer was used to study the rheology of dispersions of various fluid systems. The first group of model fluid systems consisted of the light mineral oil Exxsol D60 and blends of water and glycerol. The second system consisted of real condensate and monoethylene glycol (MEG). Dispersion viscosities derived from pressure drop measurements increased with higher dispersed phase fraction. However, the relative increase in viscosity was considerably less for the condensate – MEG system when compared with the model system. For all systems, a peak value of the viscosity was reached at an intermediate phase fraction, which was defined as the phase inversion point. For all of the systems tested, the phase fraction at phase inversion was clearly influenced by the viscosity ratio between the lower and the higher viscosity phase (μlow / μhigh).

1 INTRODUCTION

The viscosity of dispersions can significantly exceed the single phase viscosities. In real pipeline flows, the distribution of the phases in the pipe cross-section is seldom, if ever, fully homogeneous. Nevertheless, it is very useful to consider homogeneously mixed systems as an idealisation, and to apply the results locally in more complex flow situations, according to local phase fractions. For this reason, predictive multiphase flow models are dependent on either input data or reliable correlations for the dispersion viscosity. If an increased viscosity in oil-water dispersions is not considered, this will in many cases lead to considerably underpredicted pipe flow pressure gradients.

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