Multitechnical approach to the SRB MIC diagnosis and characterization for the oil and gas industry

ROBLEDO, ALEJANDRO; MASSAZZA DA; BUSALMEN, JUAN P.; ESCALADA, LISANDRO

Buenos Aires, Mar del Plata

Encuentro; 5) 34th Topical Meeting of the International Society of Electrochemistry; 2023

International Society of Electrochemistry

Microorganism induced corrosion (MIC) is considered as one of the most serious issues in the petroleum industry, accounting for more than $250 million in monetary losses each year. [1]. Sulfate-reducing bacteria are thought to be the most dangerous of the microorganisms that cause this type of corrosion because they are particularly prone to grow in the conditions created by the oil and gas industry. [2]. These bacteria can be found either supernatant in solution (planktonic) or attached to the surface forming a biofilm (sessile),which complicates evaluating the corrosive process that occurs in field-used carbon steels.The goal of this work is to investigate the process of biofilm formation from SRB and correlate it withelectrochemical results in order to diagnose and characterize SRB damage in carbon steels.To accomplish this, bacterial activity will be monitored by counting planktonic cells and sulfateconsumption in solution, as well as measuring open circuit potential (OCP), polarization resistance (PR),electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM)throughout the tests. After that, macroscopic and microscopic observations (optical-OM and scanningSEM) will be performed to observe surface damage, the presence of bacteria and the types of corrosionproducts obtained. The tests will be carried out in a four-electrode cell configuration, with SAE 1018 steelas the working electrode, graphite as the auxiliary electrode, Ag/Ag2S and Ag/AgCl as the referenceelectrodes. The electrolyte used was a modified version of the seawater medium [3] with 26 gL-1 of NaCland was kept anaerobic along the test.Figure 1A shows the biological parameters along the test duration. In the sterile condition, as expected no sulfate consumption or bacterial growth was recorded. In the medium with bacteria the changes recorded in the electrochemical parameters were coincident with a decrease in sulfate concentration, a product of bacterial respiration, and an increase in the number of bacteria in the system. Figure 1B shows that the Icorr values determined by EFM and PR techniques in the presence of SRB differed from day 7 onwards. This behavior is because in the EFM, the Icorr is overestimated while for the PR technique it is underestimated [4], thus giving us a signal for the onset of localized corrosion caused by the SRB cells.In conclusion, it has been possible to use electrochemical methods to identify instantaneously andefficiently the onset of localized corrosion, which would allow to identify and evaluate the MIC on-line