Internal corrosion of seabed ‘parked’ steel oil and gas pipelines
Robert E. Melchers
Abstract
Seabed ‘parking’ of steel pipelines is a common practice in the oil and gas industry. For ‘wet parking’ severe internal corrosion, often at the 6 o'clock position, remains an issue, despite the use of corrosion inhibitors and biocides ostensibly to control microbiologically influenced corrosion. Biocides may have undesirable environmental consequences if eventually or accidently released. Recent findings for internal corrosion inside water injection pipelines are reviewed as these have implications for managing the internal corrosion of parked pipelines. After initial oxygen controlled corrosion longer term corrosion can occur under anaerobic conditions. This has implications for corrosion during periods of stagnant conditions and for corrosion under deposits of rusts and other debris. Microbiologically influenced corrosion can increase internal corrosion but only if the nutrients necessary for bacterial metabolism are available. Acceptably low levels of corrosion can be achieved inside ‘wet’ parked pipelines with the use of seawater with low concentrations of particulate matter and low concentrations of microbiologically-critical nutrients.