Oil major Shell has been handed an improvement notice by the HSE (Health and Safety Executive) after a gas leak earlier this year.
Shell has now been ordered to make improvements by the HSE following the incident.
The operator had planned to evacuate more than 50 members of staff at the time but bad weather had prevented the safety measure.
Last year, Shell decided it was necessary to connect the Station Keeping Assist Vessel (SKAV), the Pacific Dolphin, to the Curlew FPSO because of concerns about its mooring lines.
In January this year, the towline between to two vessels snagged the gas export pipeline’s subsea isolation valve skid.
According to the notice from the HSE, the SKAV crew applied tension to the towline until the pipeline ruptured and released gas to the sea surface.
The notice said the incident could have exposed “employees and others to a risk of fire and/or explosion”.
Shell is now addressing recommendations made by the HSE.
A Shell spokesman said: “Shell received an improvement notice in relation to our management of change process for marine operations at our Curlew vessel.
“The notice refers to a gas release incident which occurred from infrastructure in the vicinity of the Curlew.
“Action is being taken to address the issues raised in the notice. The relevant authorities were informed of the incident and the matter remains under HSE investigation.”
The Curlew FPSO produces oil and gas in the central North Sea. It exports gas via the Fulmar Gas Line to St Fergus and exports oil via a tanker.
Its first production was in November 1997 and it can reach water depths of 90 metres (295ft).