Corrosion Inhibition Challenges in a Mature Subsea Production Facility

A mature field located in UK sector of the North Sea, comprises one central platform with several subsea satellite tie-backs fabricated from carbon steel. Internal corrosion mitigation of these flowlines was based on the application of a combined scale/corrosion inhibitor. Following corrosion failures at the inlet sections (towhead) of the flowlines, the requirement for an effective inhibitor increased. Subsequent inspection of the towhead pipework revealed significant preferential weld corrosion. There had been improvements in inhibitor injection compliance. However, the selection of the incumbent inhibitor was based on limited performance test work.   An appraisal of the chemical injection system and a corrosion risk assessment of the flowlines highlighted short falls in the required corrosion management process. Rectifying the integrity issues involved significant economic, operational and technological challenges that had to be overcome to achieve continued integrity of the flowlines. Hardware upgrade