DEWATERING OF CRUDE-OIL EMULSIONS .4. EMULSION RESOLUTION BY THE APPLICATION OF AN ELECTRIC-FIELD

The effect of the application of an a.c. electric field on the structure of a water-in-crude oil emulsion has been investigated both experimentally and using a molecular dynamics simulation. In both cases, long chains of droplets are seen to grow between the electrodes as a function of time. This results from an induced dipole on the water droplets in the presence of an external electric field, similar to that seen in electrorheological fluids. In the presence of a rigid interfacial film, resulting from adsorbed crude oil components such as asphaltenes, no coalescence of the drops was apparent. Simulations were also carried out to study the coalescence of water droplets in our emulsion, typical of those in which the asphaltene film was disrupted by the presence of added demulsifier. Coalescence was observed in the microscopic analysis. The results show that the solid interfacial film is a key factor for the prevention of coalescence between droplets in the electric field.