Last November two 38-m (125-ft) tubular stands on thejackupMaersk Invincible became detached from the fingerboard and fell out across the drill floor.
The upper part of the stands tumbled to the opposite side of the derrick, while the lower sections slid and struck the windshield and parts of the structure next to the gangway on the drill floor. Each tubular stand weighed around 1,300 kg.
The direct cause of the incident was the failure of the locking mechanism in the latches on the fingerboard to operate as intended.
At the time, a strong wind was also blowing in the area, and this led to the detachment.
Both stands incorporated a swell packer, a rubber seal used to isolate zones in the reservoir.
When the drilling crew realized the stands were in motion, they erected cordons to prevent access to the drill floor.
The PSA has concluded there were three breaches of regulations, namely inadequate risk assessment and decision basis; inadequate experience transfer within the company; and inadequate locking mechanism on the fingerboard.
This is not the first incident of different types of tubulars falling out of fingerboards on the Norwegian shelf, so there is a need for lessons learnt to be disseminated, the PSA said.
It has given the rig operator Maersk Drilling until April 8 to explain how it intends to address the nonconformities.