Evaluation efficiency of barium sulfate scale inhibitors by electrochemical impedance spectroscopy

Abstract

The electrochemical behaviour of carbon API 5L X70 grade steel electrode towards barium sulfate scaling and scaling inhibitors is investigated in this paper. A study of the carbon steel/injection water interface, with and without inhibitor, was carried out using electrochemical impedance spectroscopy (EIS). The scanning electron microscopy (SEM) and the X-ray diffraction study, in the absence of scale inhibitors, revealed the formation of a thick layer on the surface mainly composed of barium sulfate BaSO4. The barium sulfate scale is formed naturally and evolves with the immersion time. EIS spectra, in uninhibited medium, present three capacitive loop corresponding to transfer charge resistance, deposit resistance and porous resistance. The effectiveness of scale inhibitors used in oil fields pressure maintaining systems is evaluated. The EIS spectra in the presence of the inhibitors show the decrease of the resistances reveal that the scaling inhibitors effect is a tendency to form low amounts of barite solid precipitated on the electrode surface and their inhibiting efficiency increases with concentration rise