INVESTIGATIONS INTO THE ELECTRICAL AND COALESCENCE BEHAVIOR OF WATER-IN-CRUDE OIL-EMULSIONS IN HIGH-VOLTAGE GRADIENTS

The stability of water-in-crude oil emulsions when subjected to high voltage electric fields depends on the nature of the crude oil and the presence of chemical additives. Optical microscopy, conductivity and coalescence measurements have revealed two distinct types of behaviour, designated type I and type II. These are shown to be related to the crude oil/water interfacial rheological properties. For incompressible crude oil/water films, droplet-droplet coalescence is hindered and chains of water droplets are established. These increase the electrical conductivity of the emulsion (type I behaviour). On the other hand, efficient droplet-droplet coalescence accompanied by minimal conduction occurs in electric fields if the interfacial film is compressible (type II).