Susmitha Purnima Kotu and Jose Vera, DNV USA, Sven Lahme, ExxonMobil Corporation, and Sam Rosolina, Microbial Insights, Inc., discuss how biomarker technology may enable the oil and gas industry to swiftly diagnose microbial corrosion.
Activities during oilfield operations (such as hydraulic fracturing, wet parking, etc.) introduce moisture or water as well as various microorganisms to production infrastructures; under ideal conditions biofilms can develop on exposed steel surfaces.
The metabolic activities of microorganisms inhabiting the biofilms can generate localised differences in electrochemical potentials as they may secrete acidic metabolites or enzymes that can accelerate metal oxidation, thus posing the risk for microbiologically-influenced corrosion (MIC).
The microorganisms likely to cause MIC can thrive in a wide range of conditions – in terms of salinity, pH, temperature, oxygenation, nutrients availability, etc. – and survive in harsh environments. When the situation is unfavourable to biofilm growth, they may enter a dormant stage until circumstances allow them to flourish again, making MIC a potentially recurring issue.
Unfortunately, MIC is notably difficult to detect and monitor in oilfield installations – especially since the available molecular methods used to characterise microorganisms in such environments are limited to some subsets of the microbial groups linked to MIC, and do not create a comprehensive picture of system integrity.
Culture-based tests of water samples may be poorly representative of the biofilm communities that exist in oilfield situations. Moreover, the analysis of molecular data as well as that of data generated directly on oilfield samples typically fall short of establishing a direct correlation between microbial concentrations and actual corrosion (as exemplified by the failed attempt to consistently correlate numbers of sulfate-reducing bacteria to the occurrence of MIC in oilfield infrastructure). Consequently, current molecular methods do not provide reliable prediction of MIC or evaluation of biocide performance for MIC prevention.
At present, MIC is most commonly identified – generally through material testing and biofilm analysis – after damage has already occurred and abiotic origins have been excluded as root causes …
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