The ever increasing oil and gas exploration and production cost requires highly efficient and safe operation of the existing offshore and subsea equipment and facilities. At the same time, a large number of facilities and parts of the existing infrastructure are quickly approaching or have exceeded their originally designed service life. Many fields, however, still have large amount of remaining recoverable oil and gas reserve which can be profitable if current production equipment's service life can be extended beyond their nominal design, otherwise economic penalty of stopping production or installing new equipment will be too high.

On the other hand, once existing equipment have been operating beyond their design life, unforeseen failure and integrity problems can occur that site personnel may have not previously encountered. In many cases this can cause production to cease unexpectedly, and result in costly emergency repairs to get the asset back online.

To extend asset life and push the design envelop, operators must prove to themselves and often their regulators that the assets are safe to operate with limited and controlled risks. In a scenario like this, the subsea integrity management of ageing assets has become a key issue for the oil and gas industry.

This paper provides an actual case study for asset integrity assessment of subsea facilities life extension, performed by DNV GL and the O&G asset operator team. The study includes the asset integrity condition assessment based on equipment design documentation, operations data, maintenance and inspection analysis data, risk assessment and recommended mitigation of identified threats, engineering critical analysis of high risk equipment, and proposed destructive lab testing of parts retrieved from subsea.

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