RR1094 - Microbiologically influenced corrosion of mooring systems for floating offshore installations. Mooring Integrity Joint Industry Project Phase 2

Mooring Integrity for floating offshore installations is an important safety issue for the offshore oil and gas industry. This report is one outcome from Phase 2 of the Joint Industry Project on Mooring Integrity. This work ran from 2008 to 2012 and had 35 industry participants. It followed the Phase 1 work described in HSE Research Report RR444 (2006). The Phase 2 work compiled research on good practice and an overview is given in HSE Research Report RR1090 (2017).

Microbiologically Influenced Corrosion (MIC) is corrosion stimulated or caused by the presence of bacteria, algae or fungi on the surface of components. This report describes a study into MIC on offshore mooring system components. It is based on the literature, industry field cases and discussion with MIC specialists. It describes possible MIC mechanisms and identifies that uncertainties make it difficult to unambiguously determine whether MIC has taken, or is taking, place. It is found that although none of the field cases unambiguously confirms MIC damage, there are possible indications that sulphate-reducing bacteria play a role and that the most vulnerable parts of mooring systems may be at or just above the sea bottom and close to the splash zone. The report: sets out MIC diagnostics; outlines a draft procedure for industry inspection, testing, sampling and analysis of MIC on mooring systems; and identifies some measures that could potentially reduce the likelihood of MIC, such as avoiding pollution from oil drilling and oil production activities, or other depositions of nutrients.

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Updated 2021-04-15