Synergistic effects of mixed microorganisms on the corrosion of X65 carbon steel in actual reinjection water

Complex microbiological interactions in reinjection water can lead to severe corrosion of pipelines. In this study, X65 specimen was used for corrosion simulation experiments to explore the microbiologically influenced corrosion (MIC) and mechanism in actual oilfield reinjection water. The results of scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) showed that the X65 carbon steel was severely corroded by microorganisms, with the maximum localized corrosion pit depth of 15.04 mu m after 28 days of immersion. Electrochemical analysis and weight loss measurement further confirmed that the mixed microorganisms caused serious corrosion of X65 carbon steel, and the maximum corrosion rate was 0.249 mm/y. Furthermore, microbial community structure determination showed that mixed microorganisms in the actual reinjection water formed a corrosive biofilm on the surface of X65 steel, inducing severe pitting corrosion, which was mainly attributed to the synergistic effect of Pseudomonas, sulfur-oxidizing bacteria (SOB), sulfate-reducing bacteria (SRB) and methanogenic archaea. The results of this study have important guiding significance for the identification of MIC process for actual water samples of the oilfield and the timely adjustment of MIC control measures.