Novel Microbiological Influenced Corrosion Mitigation Strategies and Improved Microbiological Monitoring Techniques
Microbiologically influenced corrosion (MIC) is estimated to result in billions of dollars of damage annually to world-wide oil and gas facilities. Although much work has been conducted identifying the principal bacteria involved in MIC, the importance of the role of Archaea, i.e. sulphate-reducing Archaea and methanogens in MIC, has only recently been understood. Little work has been carried out investigating the efficacy of traditional MIC mitigation strategies such as biocide application on Archaea; however there is some evidence that Archaea will be more resistant to biocidal action due to the very different biochemical composition of the cell wall and membrane. A well managed biocide regime can greatly reduce the risk of MIC and maintain facilities’ integrity; however conventional biocides have drawbacks in that they are both highly toxic to humans and harmful to the environment. With many governments introducing tougher legislation for discharge of waste water to the environment, there is increasing interest amongst oil and gas companies for more environmentally-friendly biocides. One example of a ‘green’ biocide is modified chitosan. Chitosan, a deacetylated derivative of chitin, itself a constituent of crustacean shells, is a low-toxicity, biodegradable, antimicrobial polymer. Chemical modifications can produce a range of modified chitosan molecules with enhanced antimicrobial and surfactant properties. The potential use of modified chitosan for MIC control and other applications will be discussed, but noting that such techniques need further development and field trials. Finally the drawbacks of conventional microbiological monitoring using culture-based techniques are well known. Molecular microbiological based techniques are now ubiquitous in other industries but have yet to be fully integrated into the oil and gas industry. A case study will be presented whereby molecular microbiological techniques were used to solve a production problem which could not easily have been achieved using conventional culture-based techniques. Current research into state-of-the-art molecular microbiological monitoring techniques will be discussed such as 454 pyrosequencing to conduct metagenomic analysis on oilfield samples, and PMA-qPCR, a technique that allows the selective quantification of viable and non-viable oilfield micro-organisms by qPCR.