A North Sea drilling firm failed to react quickly enough in a storm which saw one of its rigs lose half its anchors, a probe has found.
The Health and Safety Executive (HSE) blamed poor procedures for the Stena Spey incident, placing the safety of the crew at risk during the furious Storm Babet in October.
Operator Stena Drilling said it viewed the findings with the “utmost seriousness” and had implemented measures in the wake of an internal investigation since the event.
Forty-five non-essential staff working on Stena Spey were airlifted to safety after four of the unit’s eight anchors became detached in the early hours of October 21.
Two Coastguard helicopters and a search and rescue helicopter were involved in the evacuation operation, which made national headlines.
A further 44 crew members stayed on board.
Stena Spey was working for Ithaca on central North Sea prospect
The severe storm hit while Stena Drilling was spudding an appraisal well on Ithaca Energy’s K2 prospect in the central North Sea, around 145 miles off the Aberdeenshire coast.
An investigation in the wake of the incident has found poor guidance procedures were to blame, resulting in Stena Drilling failing to respond quickly enough to weather warnings.
An improvement notice issued to the rig operator by HSE said it failed to provide “comprehensible instructions” on the safety actions required during weather conditions that would likely exceed safe operating limits.
Vital details missing from Stena Spey safety procedure documents
HSE said various documents covering safety processes for severe weather and environmental conditions did not include vital information, such as environmental limits for safe operation of the rig’s anchor winches.
They also contained “contradictory information” on when to prepare to shut down operations in response to weather forecasts.
It found these procedures were also written in a manner which would increase the likelihood of errors, with multiple actions detailed in single steps and “ambiguous language”. Phrases such as “timely decision” and “if the situation requires” were highlighted.
Weather forecasts from as early as October 15 indicated limits for the well riser and mooring lines were likely to be exceeded on October 19. But the installation did not unlatch from the well in sufficient time to prevent the riser being exposed to a sea state beyond its identified limits.
Nor did the rig move to “survival mode” in sufficient time to maintain its mooring systems – all of which put the safety of the rig and those onboard at risk.
Stena Drilling confirmed it was aware of the HSE notice and said it had taken the precaution of unlatching the vessel from the well in advance of the storm.
It added: “The company takes any such incident with the utmost seriousness and following its own internal investigation has initiated a number of measures to ensure both the safety of all those onboard a Stena vessel but also those who might be affected ashore.
“Stena Drilling welcomes the findings of the HSE and confirms that the safety and security of all those involved in Stena operations is its first and foremost priority.”
Rig now moored off Invergordon
Built in 1983, the semi-submersible Stena Spey has accommodation on board for up to 120 people and can drill to a maximum depth of 25,000ft in around 1,500ft of water.
According to recent satellite data, the rig is now moored off Invergordon in the Cromarty Firth.
Stena Drilling has until the end of February to improve its processes.
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