OTO 2002/014

Spool tree component reliability, failure mode identification, determination of the leak frequencies and leakage rates

Evaluates a generic horizontal spool tree and wellhead system by applying a failure mode and effect critical analysis (FMECA). The credible failure modes were identified assuming normal operating conditions. Key components and seal arrangements were identified by following the primary gas paths through the model, which was then broken up into zones to help to facilitate the FMECA. Primary, secondary and tertiary barriers between the gas and atmosphere were identified. The FMECA was performed with the aid of zone specific drawings. The side pocket mandrels located in the production tubing have been included for completeness. The FMECA identified failure modes with the potential to leak injected gas directly to atmosphere. Further leak sources were identified arising from failure of component /sealing arrangements causing injection gas to leak into the B annulus. Each of the failure modes has been reviewed to a level that permits an appropriate understanding of the failure mechanisms.

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Updated 2021-04-15