Biocorrosion: Predicting and responding to new types of microbially-influenced corrosion in the oil and gas industry

Corrosion of metals affects multiple industries and poses major risks to the environment and human safety, and is estimated to cause economic losses in excess of £2.5 trillion worldwide (around 6% of global GDP). Microbiologically-influenced corrosion (MIC) is believed to play a major role in this, but precise estimates are prevented by our limited understanding of MIC-related processes.

In the oil and gas sector biocorrosion is usually linked to the problem of "souring" caused by sulfate-reducing bacteria (SRB) that produce corrosive hydrogen sulfide in subsurface reservoirs and topsides facilities. To combat souring, reservoir engineers have begun turning to nitrate injection as a green biotechnology whereby sulfide removal can be catalysed by diverse sulfide-oxidising nitrate-reducing bacteria (soNRB). However, this promising technology is threatened by reports that soNRB could enhance localized corrosion through incomplete oxidation of sulfide to corrosive sulfur intermediates. It is likely that soNRB are corrosive under certain circumstances; end products of soNRB metabolism vary depending prevailing levels of sulfide (i.e., from the SRB-catalyzed reservoir souring) and nitrate (i.e., the engineering "nitrate dose" introduced to combat souring). Furthermore soNRB corrosion will depend on the specific physiological features of the particular strains present, which vary from field to field, but usually include members of the Epsilonproteobacteria - the most frequently detected bacterial phylum in 16S rRNA genomic surveys of medium temperature oil fields.

A new era of biological knowledge is dawning with the advent of inexpensive, high throughput nucleic acid sequencing technologies that can now be applied to microbial genomics. New high throughput sequencing platforms are allowing unprecedented levels of interrogation of microbial communities at the DNA (genomic) and RNA (transcriptomic) levels. Engineering biology aims to harness the power of this biological "-omics" revolution by bringing these powerful tools to bear on industrial problems like biocorrosion.

This project will combine genomics and transcriptomics with process measurements of soNRB metabolism and real time corrosion monitoring via linear polarization resistance. By measuring all of these variables in experimental oil field microcosms, and scaling-up to pan-industry oil field screening, a predictive understanding of corrosion linked to nitrogen and sulfur biotransformations will emerge, putting new diagnostic genomics assays in the hands of petroleum engineers.

The oil industry needs green technologies like nitrate injection. This research will develop new approaches that will safeguard this promising technology by allowing nitrate-associated biocorrosion potential to be assessed in advance. This will enhance nitrate injection's ongoing successful application to be based on informed risk assessments.

Our high living standards in the UK are inextricably linked to fossil fuel energy. Currently fossil fuels account for greater than 80% of global primary energy supply. It is widely acknowledged that this must drop, and in the future new technologies for renewable energy will be required to replace fossil fuels. But when will this future arrive? Even under optimistic projections of rapid innovation and modest global population growth, fossil fuels will still supply 70% of our energy in 2030 (International Energy Agency, 2010). It is clear that our transition towards more sustainable energy sources will require several decades and that fossil fuels will continue to be essential. It is therefore critical to UK society and the UK economy that development of new energy technology includes a focus on the fossil fuels sector so that existing resources are exploited as responsibly and sustainably as possible during this slow transition.

One of the most promising and 'green' biotechnologies in the oil industry is nitrate injection for the microbiological control of reservoir souring. This is important due to the corrosion problems that have long been linked to souring, however, recently oil companies have observed that nitrate-induced biological reactions may actual worsen corrosion problems, e.g., accelerated corrosion rates and localized 'pitting' that can lead to failures in pipelines and other production equipment. The BIOCORROSION proposal aims to understand this process of nitrate-induced corrosion such that the ongoing use of nitrate-based bioengineering in the oil industry is safeguarded.

Corrosion problems affect many industries, not just the oil industry. The scale of the damage caused by metal corrosion is vast with many sectors of the economy suffering losses due to corrosion problems. On a global scale, corrosion losses exceed £2,500,000,000 per year. In the UK the main sectors that are regular victims of corrosion damage include public utilities as well as the construction, marine, transportation and oil and gas industries. Corrosion damage can lead to economic losses in a variety of ways including shutdowns, replacement costs, corrosion prevention coatings, structural failures and the release or spills of products. This list reflects that corrosion is not only an economic problem, but is also associated with significant health and safety risks.

By focusing specifically biocorrosion catalyzed by sulfide-oxidizing nitrate-reducing bacteria (soNRB) this research will be most relevant to the energy sector and engineers working in oil and gas production. As such, the main beneficiaries of the research will be oil companies. The UK hosts a major offshore oil industry that contributes significantly to national employment and economic prosperity. UK-based partners on the PI's Career Acceleration Fellowship include Shell, Chevron North Sea and Rawwater Engineering Ltd. These and other stakeholders represent beneficiaries that the PI has direct contact with.

Impact will be achieved primarily through participation at industry meetings and forums including those that publish conference proceedings that are widely read within the oil industry (see Pathways to Impact document). Furthermore, the team will strive to publish BIOCORROSION research in high impact peer review journals and present results at prominent environmental microbiology conferences (see Academic Beneficiaries section).

Additional beneficiaries will include policy makers focused on understanding the extent of economic losses due to corrosion (see above) and who may be undertaking materials standards regulations related to corrosion ratings of metal equipment.