While Sjoborg was loading/discharging alongside Statfjord A, power was lost to two of three bow thrusters. The vessel thereby drifted off its position and collided with the facility.
Equinor Energy (Equinor) is the operator for Statfjord. Sjoborg is owned and operated by Skansi Offshore.
Actual and potential consequences
A member of Sjoborg’s crew was hit in the face by a diesel hose. Under slightly different circumstances, this incident could have had a fatal outcome.
Sjoborg suffered extensive damage to mast and equipment above the bridge, and denting to its starboard side aft.
One of Statfjord A’s lifeboat stations was damaged.
There were 276 people on the facility when the collision occurred. Damage to the lifeboat station, with consequent reduced lifeboat capacity, meant that 218 people were evacuated by helicopter to other facilities in the area. Fifty-eight people remained on Statfjord A.
Material damage could have been even greater had it taken longer to restore sufficient control to move Sjoborg away from Statfjord A.
Other weather conditions, for example, could have made such a move more demanding.
Direct and underlying causes
The direct causes of the incident were drifting as a result of inadequate thruster power and the location of the loading/discharge operation on the windward (weather) side.
Several underlying causes resulted in insufficient thruster power. This can be related to failure of or incorrectly installed equipment components, disruption from defective components which led to network failure in the blackout safety system (“network storm”), loss of network frequency measurement on the main switchboard, activation of the load-reduction mode and restriction of all thrusters to 10-15 per cent of maximum output, nonconformity between DP commands and rpm feedback from all thrusters, and automatic shutdown of thrusters 1 and 3.
Nonconformities and improvement points
The investigation has not identified breaches to the regulations, but the PSA team observed improvement points in two areas – compliance with activity-specific operational guidelines and the handling of bulk hoses.
What happens now
The PSA has completed its investigation. Equinor has been asked to provide its assessment of the improvement points observed.
On the basis of its own investigation, Equinor has recommended three improvement packages for learning lessons which will help to concentrate greater attention on the role of DP system integration and to improve the quality of such integration, and will communicate experience from evacuation and transfer.
The PSA has asked Equinor to submit a plan which establishes a timetable for implementing recommended measures, and which describes how the measures will be implemented in relevant parts of the company’s units.
Equinor has been given until 13 December 2019 to respond to the PSA on these points.
Statfjord is a field in the Tampen area in the northern part of the North Sea, on the border between the Norwegian and UK sectors. The Norwegian share of the field is 85.47 per cent. The water depth in the area is 150 metres. Statfjord was discovered in 1974, and the plan for development and operation (PDO) was approved in 1976.
The field has been developed with three fully integrated concrete facilities: Statfjord A, Statfjord B and Statfjord C. Statfjord A, centrally located on the field, came on stream in 1979. Statfjord B, in the southern part of the field, in 1982, and Statfjord C, in the northern part, in 1985.