Microbiologically Influenced Corrosion (MIC) is considered as one of the more notorious corrosion mechanisms as it results in the characteristic pitted-type of corrosion and is therefore often very difficult to predict. Among several environmental parameters, risk for MIC is therefore most often identified based on enumeration of MIC-related microbes (Sulfate Reducing Prokaryotes (SRP), Methanogenic Archaea (MA), etc.). Historically, the enumeration of microbes was performed through use of dilution or Most Probable Number (MPN) series. More recently, however, DNA-based methods like Fluorescent In-Situ Hybridization (FISH), quantitative PCR (qPCR) and metagenomics have been applied. Although these new DNA-based methods are promising, there are also cases where inconsistencies have been experienced. Several case studies showed that qPCR for specific microbial groups such as; SRP, MA, and Nitrate Reducing Prokaryotes (NRP), is unreliable due to the lack of adequate coverage of the target microbial community. As such the claims of DNA-based methods, to be more accurate and indicative, are not always properly met.

The current study proposes an improved biomonitoring standard (data analysis and reporting) that is based on the combination of qPCR (for Total Bacteria and Total Archaea) and single gene (16S rRNA) metagenomic data analysis for the purpose of MIC risk assessment. It also aims to generate ‘calculated numbers’ for oil field relevant microbial groups by combining qPCR counts for Total Prokaryotes and relative abundance (%) of the respectively individual bacterial and archaeal microbial families and genera from single gene (16S rRNA) metagenomic analysis.

The ‘conventional’ qPCR approach (on functional genes) and proposed method are compared through a field case study. In contrast to the ‘conventional’ qPCR approach, the proposed method resulted in reliable, internally consistent and better interpretable results, indicating MIC to be the root cause of a pipeline failure. The proposed biomonitoring standard has been communicated with several biomonitoring service providers that are used by the different oil majors. The proposed biomonitoring standard is aimed to be used as the improved cross-business standard for biomonitoring for the purpose of MIC risk assessment and as such to be implemented in existing NACE standards.

You can access this article if you purchase or spend a download.