Proceedings of the
European Safety and Reliability Conference (ESREL2026)
14 – 19 June 2026, Braga, Portugal
Subsea tree valve inspection and maintenance optimization using varying inspection intervals
Department of Geoscience, Norwegian University of Science and Technology, Norway.
Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, Norway.
Department of Geoscience, Norwegian University of Science and Technology, Norway.
ABSTRACT
Condition-based maintenance (CBM) allows us to identify and rectify potential well integrity issues on a well for safe operations and prolonged well barrier health. The Christmas tree (XT) valves provide the final well barrier on a well and are key in preventing hydrocarbon release to the environment. Choosing the right maintenance and inspection policy is essential in reducing both the failure risk and maintenance costs, albeit with increased availability of the XT system. This paper proposes a varying inspection XT valve maintenance policy that achieves these objectives. Results show that after a failure, the 90 -day inspection interval achieves approximately a similar probability of failure on demand and lower cost than the 30 and 90-day inspection intervals recommended by NORSOK-D010. The varying inspections model can find application in late-life well integrity management by matching the inspection intervals with the failure rate of the well barriers.
Keywords: well integrity, xmas tree valves, maintenance.
