After a three-month internal investigation, Norwegian oil and gas group Statoil said that a condensate leak on the Gudrun platform in the North Sea on 18 February 2015 had been classified to be of the highest degree of seriousness.
According to the investigation report, on the morning of 18 February 2015 noise and vibrations were reported on Gudrun. Shortly afterwards, hydrocarbons were confirmed in the process module.
There was a 2 mm wide crack extending approximately 90% across the circumference of a two-inch pipeline. Condensate had leaked from the pipeline and resulted in gas distribution. The actual leak rate was calculated to be around 8 kilogram/second. The volume of condensate from the leak was estimated to be 4 cubic metres.
No one was physically injured as no personnel were present in the area. The investigation concluded that the outcome could have been fatal if anybody had been exposed to the leak. A gas leak of this size represents a major incident potential if ignited, the report said.
“The condensate leak on Gudrun was serious with major incident potential,” says Øystein Arvid Håland, senior vice president of safety and sustainability of Statoil business unit Development and Production Norway (DPN).
“Statoil is working systematically on gas leak prevention, and the learnings from this incident shall be translated into specific actions. We must ensure that these efforts help prevent future incidents.”
Based on technical investigations, the crack was found to be the result of fatigue and overload. An under-dimensioned level valve led to vibrations in the valve itself and in the surrounding piping system during regular plant operation.
The vibrations resulted in loss of level valve control which caused repeated powerful vibrations and strokes in the piping system which exceeded the design capacity.
No material defects, metallurgical irregularities or welding defects were proven. The investigation team said they believed that pure chance prevented a full pipeline break.
Gas detectors recorded the leak, ignition sources were disconnected and the deluge system started automatically, as did the pressure relief system and the emergency shutdown system.
“I am glad that no one was physically injured,” says Bente Aleksandersen, senior vice president of the operations south cluster of DPN.
“The investigation gives us valuable information to learn from and it is our responsibility to use this information both in Statoil and towards the Petroleum Safety Authority Norway and other players in the industry to prevent a recurrence of this type of incident. When the leak occurred, the emergency response system functioned as intended.”