Difficult to detect and monitor, microbiologically influenced corrosion (MIC) refers to bio-corrosion that occurs when microorganisms break down materials. It poses a significant problem in numerous industries, so taking early action to mitigate its effects can protect the environment and operations by reducing the risk of costly pipeline or storage/process tank failures.
Unfortunately, while molecular methods for the detection and characterisation of microorganisms in oil field waters have emerged, the data tends to correlate poorly to system integrity and is not currently suitable as a leading indicator for MIC. Instead, the diagnosis of MIC is typically through analysis of metal-associated biofilms after damage has already occurred.
A new joint industry project (JIP) aims to develop the next generation of MIC detection, monitoring and mitigation technology. The principal JIP stakeholders are DNV, an independent energy expert and assurance provider, ExxonMobil Upstream Research Company, and Microbial Insights Inc.
Dr Susmitha Purnima Kotu, DNV JIP lead, says: “Just the presence of micro-organisms inside pipelines does not necessarily mean there is corrosion. We need better detection of MIC because existing methods do not tell us the full story. Industry needs to know if micro-organisms are causing corrosion and the severity of that threat.”
In 2020, ExxonMobil discovered certain DNA-based biomarkers in laboratory tests samples taken from an oil field in West Africa. The biomarkers correlated to corrosion, with subsequent validation from testing on field samples from several other geographical locations and field service conditions.
“After ExxonMobil published a paper on their findings, we used the biomarkers in some of our failure analysis work,” explains Kotu. “We do a lot of MIC assessment and management studies, and had great success in using those biomarkers. So we decided to form a JIP with ExxonMobil. The other partner is Microbial Insights, which specialises in PCR and DNA sequencing analysis. As a JIP we want to get samples from several different service conditions that provide an understanding of the worst-case MIC scenario for oil and gas operators and identify further biomarkers.”
DNV programme manager Jose Vera takes up the story: “We know that if we find the biomarkers identified by ExxonMobil, we have corrosion. But if we don’t find them, we can’t be sure that we don’t have corrosion because there could be other, yet unidentified biomarkers out there. That is our focus; we expect to find a further 5-10 biomarkers that will provide a full picture of whether an MIC problem exists.”
1,200 DATA POINTS
The JIP aims to create 1,200 data points of corrosion-to-biomarker correlations, generated on simulated pipelines with actual field waters and participant-selected service conditions. Says Kotu: “Through laboratory testing on samples we can characterise the types of micro-organisms and the chemical factors that could be causing corrosion,” says Kotu.
Corrosive gases can often come from abiotic sources such as CO2 and H2S, both of which are common in oil field systems. The JIP test set-up can simulate concentrations of CO2 and H2S, with a control step running in parallel. Here, the DNV team can sterilise samples to remove the component of microbial corrosion and see the contribution of abiotic corrosion sources. Each test run will take several months.
The team aims to develop methods, tools and workflows (‘biomarker technology’) to improve the reliable detection of MIC in oil field operations, heavily leveraging advanced laboratory bioreactors and molecular analytical platforms that have been specifically developed for MIC biomarker discovery and KPI development.
“For the integrity management of assets we must develop KPIs to interpret what the quantity of the biomarkers present in a sample really mean in terms of corrosion,” explains Kotu. “The ability to provide a direct correlation between biomarker data and corrosion is precisely what’s missing right now.”
MAJOR IMPACT
The success of this JIP could have a major positive impact across industry, particularly with regard to safety, asset protection and sustainable operations.
Christopher Kagarise, senior engineer at DNV, says: “The new biomarkers will become a leading, rather than a lagging indicator. Right now I feel we are behind and trying to play catch up. Corrosion has to be severe enough to detect, at which point it may be too late for prevention strategies. In the near future, using the new biomarkers, maybe we can get ahead of the game and prevent corrosion before it becomes an issue.”
Adds Kotu: “We anticipate starting the project before the end of 2022 and we’re currently engaging potential project participants with a history of asset MIC. It will take around three years to complete all the testing. However, we will likely develop biomarkers in the first 6-12 months. Those participating in the JIP will be able to use those biomarkers as soon as they are developed.”
The new biomarkers could also be used to monitor and manage MIC for other applications, including underground gas storage, offshore wind turbines, cooling water plants, water storage tanks, drinking water pipelines, ship hulls and fuel tanks, although Kotu states that testing will of course be required.
Richard S Barnes, region president, energy systems North America at DNV, concludes: “By working with ExxonMobil Upstream Research and Microbial Insights we will unravel the most relevant MIC mechanisms prevalent in oil and gas operations to better understand their impact on corrosion. The focus is to develop leading indicators that allow operators to develop and implement the right approach to address MIC in its earliest stages, protecting people and the environment while ensuring continuous, safe operations.”
BOX: MIC and the aerospace industry
According to Nycote Laboratories Corporation, a surface coating manufacturer, billions of dollars have been dedicated to understanding how microorganisms affect different industrial materials. Estimates suggest that about 20% of all corrosion failures are due to MIC.
Pennie Burnham, VP of sales and market research at Nycote, reports: “MIC prevention should start with ideal material selection. For instance, integral fuel tanks are typically made from 3003 or 5052 aluminium alloy or stainless steel. As organisms grow, they become slimy biofilm mats that can cause considerable damage. To remove microbial black sludge from fuel tanks, maintenance teams must clean, treat and reseal all affected parts and systems. Unfortunately, integral fuel tanks are permanent fixtures and are not easy to inspect, maintain or repair.”
In answer to this challenge, Nycote has coatings that protect against the destructive effects of MIC. Nylon is naturally microbe-resistant: when formulated into a precise coating, it provides an effective barrier between aircraft parts and the environment. To prevent MIC, Nycote 7-11 has been applied to fuel tanks and containment system parts for decades. Today, use cases for Nycote 7-11 have evolved into applications including electrical systems, avionics, drain masts and sensors. The company reports that its latest-generation products like Nycote 99 Ecoshield and Nygone have delivered excellent results at aerospace OEMs.