Corrosive differentation of SRB isolated from injection waters used in secondary crude oil recovery

Abstract

The purpose of this study is to differentiate the corrosive aggressiveness on iron of two predominant types of Sulphate Reducing Bacteria: SRB, Desulfovibrio (D) desulfuricans and D. termitidis, found in the injection waters frequently, using measurement of open circuit potential, ohmic drop, weight loss, Tafel polarization, polarization resistance and electrochemical impedance. The attack morphology was also studied over time through optical and scaning electron microscopes, every 3 hours during 24 hours. Additionally, a comparison was made among the different electrochemical techniques applied to establish which of these is the most appropriate and reliable for evaluating MIC processes. Results obtained showed values of weight loss and corrosion rate increasing up to 9 hours, at which time they began to decrease, reaching a minimum close to 15 hours of exposure, and then increasing up to the end of the experiment at 24 hours, with D. termitidis always demonstrating greater aggressiveness, a fact corroborated by observed the attack morphology. Of the techniques used for measuring corrosion rate, it was established that weight loss and Tafel polarization reflect most appropriately the best behavior of iron exposed to a medium inoculated with sulfate-reducing bacteria (SRB) and ferrous ions.

Keywords

• microbiologically induced corrosion
• SRB
• corrosion rate
• electrochemical techniques
• injection waters
• crude oil recovery