Failure of 38 inch dry gas injection pipeline: black powder corrosion mechanism

摘要

A 38 inch gas injection pipeline failed in less than six month of operation. The 45 km line transported a mixture of richnassociated gas (RAG) from a stripping plant to injection wells. The problem was identified when a cleaning pig wasnintroduced into the pipe as a precursor to an intelligent pigging operation. The pig became lodged at the 7 km point withn7 tonnes of corrosion material in front of it. Remedial action response teams had to cut the pipe to remove the pig andncorrosion material.nInvestigation of the pipe interior revealed over 10,477 locations of pitting over the 45 km length of the pipeline, withnsome locations where the metal loss exceeded 40 per cent. The sulphide-based corrosion product was identified asnblack powder. The pipeline engineers believed such a mechanism would not have been a possibility as the gas beingntransported was dehydrated to -21 degrees Celsius. This article is a brief review of the corrosion failure study conductednby Qatar Petroleum’s corrosion engineering team.