Electrochemical impedance spectroscopy of water-in-crude oil emulsions

Resumo

We conducted a study of Electrochemical Impedance Spectroscopy on water-in-crude oil emulsions based on a heavy oil sample from the Orinoco Belt. Electric impedance measures were obtained by means of an HP 4192A impedance analyzer and a stainless steel coaxial cylinder capacitor; due to impedance coupling between the analyzer and the sensor, the frequency range was taken from 75 kHz to 4 MHz. Impedance modulus and phase angle of the studied samples showed that the composed system behaves like an ideal capacitor filled with dielectric. Overall, the dielectric permittivities of samples, real and imaginary part, increase with the water contained in emulsions. The electric conductivity of all emulsions increase with frequency. The experimental data was fitted to Wagner’s theory and Hanai’s theory, finding a good correlation with the high frequencies Hanai model at water concentrations lower than 30%.