Failure of moorings during heavy weather

Offshore winds from the northeast had increased throughout 2 February 2021 and by 1800 were between 50-55 knots. At about 1915, VALARIS DS-4’s moorings failed during storm force winds. The drill ship was blown off the jetty and drifted to the southwest until about 1923, when the anchor, which had previously been deployed as part of the VALARIS  DS-4’s mooring arrangements, held. This likely prevented the drillship from going aground on an island about 400m to the west. Another similar drill ship ENSCO DS-8 remained moored alongside the jetty with tug assistance and the use of its thrusters.

VALARIS DS-4’s crew were able to start all but one of the drill ship’s diesel generators but did have difficulties bringing the bow and stern thrusters online. VALARIS DS-4 was re-moored after the crewmembers were able to start all but one of the azimuth thrusters.

The investigation revealed the following causal factors:

• the inability of crew to bring the thrusters online in time to prevent the mooring lines from being overloaded by the storm force winds from the northeast.
• the Master did not request tug assistance when the weather forecast for storm force north easterly winds was received on the afternoon of 2 February 2021.
• Additional factors identified included:
  • inadequate coordination between vessel management and the port
  • inadequate identification and consideration of local conditions, including the weather
  • inadequate identification of the drill ships’ power requirements
  • not following the original mooring plans.

(what reduced the adverse consequences of this marine incident)

• Anchors had been pre-deployed when the drill ships were berthed.
• The arrival of tugs to hold ENSCO DS-8 alongside the berth.