Six months after her capsize near the Chevron drilling rig, Transocean Rather, 85 miles west of the Shetlands on April 12 this year, a preliminary report on the AHTS Bourbon Dolphin incident and the loss of eight lives, including a 14 year old schoolboy has been released. It may raise more questions than it answers and those may have to wait until the official Norwegian report is issued next year.
Of those on the bridge when she capsized, only the second mate, Geir Syversen, survived. His testimony indicates that problems began at a very early stage and emergency systems triggered just before the capsize did not work.
Syversen and the first mate took over from the Captain and another officer at around mid-day. There was a 32 knot wind from the south-west with a significant wave heightof 2.9 metres. Some 912 metres of anchor chain had been let out, the deck crew felt it was safe to continue and attached a further 900 metres of chain, which they completed by 1300.
At 1500, as the chain was being let out, another anchor handling tug, the Highland Valour, was asked to assist by putting down a grapnel to 750 metres to lift the chain and ease the tension. The Highland Valour secured the chain but dropped it after two or three minutes and began to drift at high speed towards the Bourbon Dolphin. Collision was prevented by the first officer on the Dolphin who applied full ahead.
The movement alerted the captain of the Bourbon Dolphin, who returned to the bridge. By now some 1,500 metres of chain had been let out and the ension had reached 180 tonnes. It was agreed to let Highland Valour attempt to secure the chain again. The Highland Valour failed four times to catch the chain.
At 1545 the Bourbon Dolphin’s engineer called the bridge requesting that thruster capacity be reduced due to overheating. The First mate said it was not possible to do so because the vessel was too far out of position.
Highland Valour secured the chain on the fifth attempt. At around 1645 the Highland Valour was asked to move in a north-westerly direction towards the Bourbon Dolphin’s port quarter. Instead she moved to the south-east, pulling the Bourbon Dolphin to port. On VHF the captain asked Highland Valour whether she knew the difference between north, south east and west and the vessel changed direction.
Five minutes later the Bourbon Dolphin Chief Engineer warned that unless thruster capacity was reduced he would have to cut to avoid damage.
By now the Bourbon Dolphin was on a heading of 324 with a yaw between 324 and 330, had a slight tilt to port and had laid down 1,800 metres of chain.
Again, the Highland Valour dropped the chain. Tension on the chain reached 290 tonnes, almost a hundred tonnes more than her rated bollard pull. The First officer started pumping ballast to the starboard tanks to counter an increasing tilt to port.
At 1700 the Chevron rig realised the Bourbon Dolphin was in trouble and suggested lowering the inner starboard towing pin. The First Mate attempted to push down the lever to lower the pin but couldn’t – tension was now 330 tonnes.
The Captain turned the tug to starboard, easing the tension enough for the First Officer to push down the inner starboard towing pin. The chain moved over to the outer port towing pin, but not over the cargo rail, causing the Bourbon Dolphin to list more to port. With the vessel being pulled to port and large parts of the cargo deck now underwater, the Chief Engineer telephoned the bridge to say that both engines had stopped.
As the list to port became more extreme, the Captain ordered the second officer to push the emergency release button that would release the whole chain to the bottom but nothing happening, the chain was moving off the tug at 12 metres a second.
The Bourbon Dolphin’s fate was already sealed as, over the next few seconds, she turned turtle.
No specific cause is identified in the preliminary report but stability problems possibly due to the partial filling of the starboard ballast tank may have contributed.
There will, however, be plenty of questions.
One question will be whether it was good judgement to use the Bourbon Dolphin for the task in the first place. Bourbon offshore managing director Trond Myklebust told the inquiry that the vessel was considered ‘marginal’ and was well down the list of choices for the job.
Initially, two other vessels were intended to do the job and the Dolphin was to assist. At some stage during the operation she became, for reason still unclear, the main vessel.
Concern about the Dolphin’s suitability centered on the charterer’s specification for a vessel with a minimum bollard pull of 180 tonnes. Although the Dolphin had 194 tonnes bollard pull this was substantially reduced with the thrusters going.
A further issue was raised by a member of the Royal Commission hearing the evidence who pointed out that in the Norwegian sector operations would have been halted with six metres waves but there were no such limitations in the British sector.
Also under scrutiny will be the actions of the Highland Valour and the anchor handling competency of those aboard the Bourbon Dolphin.