Silent Threats: Tackling Microbially Influenced Corrosion (MIC) in Oil and Gas Export Pipelines

21 Jul 2026

Uncovering hidden microbial corrosion risks and the solutions that protect pipeline performance.

Export pipelines represent the final stage of the offshore process on many offshore installations They are used to send processed hydrocarbons, such as crude oil, natural gas, condensate, and produced water, to other platforms for further processing or to onshore terminals to be refined into their usable products.

These pipelines form the final transportation link in offshore production systems, engineered to operate safely under high pressures, corrosive environments, extreme temperatures, and deepwater conditions. Often located in remote and hard-to-access areas—whether subsea or across long-distance onshore routes—export pipelines can be difficult and costly to inspect, maintain, and repair if failures occur.

Therefore, it is important to continue implementing risk mitigation measures for these pipelines, especially around Microbiologically Influenced Corrosion (MIC), even after upstream processing has reduced many of the conditions that support microbial growth.   

Why could Export Pipelines become Microbial Hotspots

Water content plays a key role in microbial proliferation, as even the smallest volumes can support microbial activity. Although every effort is made to remove as much water as possible via the process, such as through separation processes discussed in our previous blog 'More than Just Oil and Water: The Microbial Challenge in Production Separators', the process is never completely effective.

Over time, this residual water may accumulate and separate from the hydrocarbon stream due to factors such as pressure fluctuations, temperature variations, and changes in flow rate. It tends to settle in low points of the pipeline, creating stagnant zones where microorganisms can thrive and form biofilms.

Biofilms are well established as a major contributing factor to MIC due to the anaerobic environment they can create, which are perfect for sulphate-reducing bacteria (SRB) and other anaerobic microorganisms’ proliferation.  The metabolic by-products produced by these microorganisms can lead to aggressive localised corrosion in steel pipelines.

Although SRB are among the most recognised microorganisms associated with MIC due to their production of hydrogen sulphide (H₂S), other microbial groups can also contribute to pipeline degradation. These include acid-producing bacteria (APB), which generate corrosive organic acids, methanogens that may contribute to metal loss, and sulphur-oxidising bacteria (SOB), which can produce corrosive sulphuric acid under certain conditions.

Together, these microorganisms can form complex biofilm communities that accelerate corrosion and make mitigation more challenging. 

Plan for success: Strategies for Mitigation

Typically, Export pipelines are in areas that are not easily accessible due to the long distances they are required to transport hydrocarbons. In the case of the North Sea these pipelines are commonly installed on the seabed as subsea infrastructure. As a result, identifying pipeline failures is far more challenging than on topside systems, where equipment is visible and regularly inspected by personnel.  If a failure were to occur it would also increase the potential financial impact of any outage, particularly if production must be shut down for repair.  This makes effective monitoring, inspection, and corrosion mitigation strategies especially critical for maintaining pipeline integrity and minimising operational downtime.

As highlighted mitigation can be challenging within export pipelines compared to the topside process systems however, there are still options available. 

Pigging is perhaps the most well-known and effective way of mitigating MIC risk within export pipelines. A pipeline “pig” is launched into the system and driven by product flow to remove deposits such as debris, wax, and biofilm from internal surfaces. The collected debris and wax often termed "Pigwax" is then deposited at the pig receiver by the pig and disposed of. Samples of this "pigwax" can be analysed for microbial activity, sulphide levels, or compositional analysis. This provides valuable insight into MIC risk and supports targeted treatment strategies.

Pigging tools range from simple foam pigs to advanced intelligent pigs capable of measuring wall thickness and detecting defects, providing critical data for integrity management. Regular pigging helps prevent biofilm accumulation, a key driver of MIC as discussed in our Case Study 'Microbes vs Pipelines: Using molecular methods to Track Corrosion Culprits'.

Biocide application is commonly used alongside pigging operations. Pigs are often pushed through the pipeline using an extra surge of treated seawater to reach the high pressures needed to launch the pig into the pipeline. Treating this seawater with biocide provides two key benefits. One, preventing the introduction of additional microbial contamination. Two, delivering biocide to areas that have been cleaned by the pig, and aiding in the reducing recolonisation and targeting planktonic microbes in the system.

Operational performance and design can also play a role in mitigation of risk. Selecting the right construction materials such as corrosion resistant alloys or the addition of internal coatings and linings to pipes helps prevent corrosion. Maintaining sufficient flow velocity helps with dissuading sessile populations from being able to colonise the internal surfaces. Designing systems to minimise low points where water and microbes could accumulate.

Hidden but not Forgotten: MIC risk a final word

With aging platforms comes increased risk of MIC through many avenues and while the focus may be on the topside processes which are visible, the often-hidden subsea infrastructure should not be forgotten. MIC is a gradual beast and often the threat is not realised until it is too late! Export pipelines form one of the crucial points in the production chain and as such should be protected proactively rather than reactively when significant problems may have already occurred.

Routine sampling, monitoring, and integrity assessments provide early warning indicators of MIC risk and enable timely intervention. Ultimately, effective MIC management is not just about corrosion control—it is about ensuring long-term operational reliability and safeguarding production continuity. 

Our team can support the development of tailored monitoring programmes and assist with the collection and testing of oilfield sample to enable more informed, data-drive decision.

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