Corrosion Management of Aging Assets from the New Operator's Perspective

摘要

"Ageing is not about how old your equipment is. It is about what you know about its condition, and how that's changing over time - UK HSE RR509 Plant Ageing." Many assets in the UK sector of the North Sea are approaching or have passed their intended design life. The general decline of many mature assets has been reversed as new operators invest significantly to increase asset life when compared to the former owners. This poses a number of challenges for continued corrosion control. Operational conditions are likely to have changed radically since original design and assets may be subject to increased water cuts and requirements for gas lift and water injection. The new duty holder of a mature asset must take these factors into account when formulating their own corrosion management system. In 2008, the Company acquired the Cormorant Alpha, North Cormorant, Eider and Tern platforms and the associated pipelines and subsea tie backs. The oldest of these platforms came on line in 1978 and has passed its original design life of 30 years. The purchase also included a share of the Brent main oil line (now operated by the Company) and a share of the Sullom Voe oil terminal. The previous operator had defined these assets as "end of life". The Company needed an extended life to 2025. This required a substantial re-alignment of corrosion management priorities. Extensive rework of documentation was performed to create a corrosion management system for both pipelines and assets in accordance with recent United Kingdom government and industry recommendations. Government requirements for life extension (KP4) were assessed and the implemented. KPIs, corrosion control matrices, corrosion mitigation measures and corrosion monitoring were redefined and re-engineered to take into account both extended life requirements and future as well as present operating conditions. Materials of construction were re-assessed for compliance with ISO 15156/NACE MR01752, given the increasingly sour production conditions due to field souring. This publication discusses the issues described above, and the changes in corrosion and integrity management that were required to ensure compliance with the required life extension.