Control of internal corrosion in multi-phase oil and gas pipelines
S.Nesic, Arne Dugstad and Liv Lunde

In many subsea projects under development the pipeline costs are a considerable part of the investment and often become prohibitively high if the corrosivity of the fluid necessitates the use of higher-quality steel than carbon steel. The selection of the steel is often based on corrosion rate calculations with models which, in many cases, are conservative and cause disregard of carbon steel under conditions where it could be adequate. Better understanding and control of the corrosion of carbon steel can increase its application range and therefore have a large economic impact. The phenomena associated with material loss in a multi-phase pipeline are very complex, involving the chemistry of the pipeline fluids, the metallurgy of the pipeline material, and the pipeline hydraulics, which all interact in a complex way.Inhibition of corrosion and inhibitor distribution along the pipeline are also fields of special concern. Some of the fields which are developed or being developed or being considered for transport of unprocesses hydrocarbons in the Norwegian sectorof the North Sea are briefly described, and new aspects of the internl corrosion management of flow, or pipelines for specific fields, are discussed.

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