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Investigation of the incident on Maersk Invincible

The Petroleum Safety Authority Norway (PSA) has completed its investigation of the incident on mobile drilling facility Maersk Invincible on 11 November 2018, when two 38-metre tubular stands fell across the drill floor.


During a completion operation on the Valhall field on 11 November 2018, two lengths of made-up tubing became detached from the fingerboard on Maersk Invincible and fell out across the drill floor.

The upper part of these tubular stands fell across to the opposite side of the derrick. Their lower section slid and hit the windshield and parts of the structure by the gangway on the drill floor.

Each stand was 38 metres long and weighed about 1 300 kilograms.

Cause
The PSA’s investigation shows that the direct cause of the incident was the failure of the locking mechanism in the latches on the fingerboard to operate as intended. A strong wind was also blowing in the area at the time, which caused the two stands to detach from the fingerboard and fall out across the drill floor.

Both stands which became detached incorporated a swell packer, a rubber seal used to isolate zones in the reservoir.

The relevant section of the fingerboard with latches is intended for casing, while the stands which became detached were production tubing with a narrower diameter.

Consequences
The incident caused no injury to personnel.

People were present in the area around the drill floor. When the drilling crew understood that the stands were in motion, however, it was decided to erect cordons to prevent access to the drill floor.

The incident caused minor material damage.

Nonconformities
The PSA’s investigation identified three breaches of the regulations. These were:

  • inadequate risk assessment and decision basis
  • inadequate experience transfer within the company
  • inadequate locking mechanism on the fingerboard.

Next steps
The cause of the incident was communicated and discussed with the relevant players early in the investigation, and the PSA has received feedback that measures have been initiated.

Several incidents involving different types of tubulars falling out of fingerboards have occurred. The Maersk Invincible accident and earlier incidents demonstrate a need for learning and experience transfer both within and across the companies.

The PSA investigation has now been completed.

Maersk Drilling Norge, which operates Maersk Invincible, has been given until 8 April 2019 to explain to the PSA how it intends to deal with the nonconformities

Øyvind Midttun, press contact
Email: oyvind.midttun@ptil.no | +47 51 87 34 77