Characterization of microbiologically influenced corrosion potential in nitrate injected produced waters

摘要

Microorganisms are notorious for being involved in serious metal infrastructure damage, popularly known as microbiologically influenced corrosion (MIC). Long term corrosion incubations (~2 years) with carbon steel (CS) beads were established using produced water collected from a Canadian oilfield where nitrate was routinely used for souring mitigation. Experiments were set up under methanogenic, sulfate-reducing, and nitrate-reducing conditions to stimulate electrical MIC (EMIC) with iron present as the sole electron donor. Microbial community analysis, chemical measurements, metal weight loss, and surface analyses were conducted to assess EMIC under these different conditions. After 2 years, incubations in the nitrate-reducing environment did not show surface damage to the CS beads nor substantial weight loss (2-3%). However, incubations in the sulfate-reducing environment showed 5-8% weight loss with severe pitting on the CS beads and community sequencing revealed the predominance of known acid producers (Mesotoga, Acetobacterium), methanogens (Methanosaeta), and sulfate-reducers (Desulfovibrio, Desulfobulbus). Incubations in the methanogenic environment also showed comparatively less weight loss (2%) though surface analysis revealed an abundance of pinhole-like pits; microbial communities were dominated by putative syntrophs (Petrimonas, Pseudomonas, Desulfovibrio) and known methanogens (Methanosaeta). In addition to the establishment of promising new EMIC enrichment cultures, this study demonstrated that the localized effect of MIC cannot be accurately assessed solely using weight loss corrosion assays, but additionally requires microscopic and/or surface studies along with an understanding of the microbial community composition.