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 structu re of a water-in-crude oil emulsion has been investigated both experim entally and using a molecular dynamics simulation. In both cases, long chains of droplets are seen to grow between the electrodes as a funct ion of time. This results from an induced dipole on the water droplets in the presence of an external electric field, similar to that seen i n electrorheological fluids. In the presence of a rigid interfacial fi lm, resulting from adsorbed crude oil components such as asphaltenes, no coalescence of the drops was apparent. Simulations were also carrie d out to study the coalescence of water droplets in our emulsion, typi cal of those in which the asphaltene film was disrupted by the presenc e of added demulsifier. Coalescence was observed in the microscopic an alysis. The results show that the solid interfacial film is a key fact or for the prevention of coalescence between droplets in the electric field.