Statoil launched its own investigation following a condensate leak on the Gudrun platform in February 2015 and found it to be of the highest degree of seriousness that could have been fatal.
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Gudrun. From Statoil. |
The platform in located in the high-pressure, high-temperature Gudrun field in the Norwegian sector of the North Sea, about 55km north of Sleipner, in production license 025. The pressure in the reservoir is about 860 bar, with 150°C temperatures.
According to the investigation conducted by Statoil’s corporate investigation team, at 6:40 a.m. of 18 February, noise and vibrations were reported on Gudrun in which hydrocarbons were confirmed in the process module shortly after.
A 2mm wide crack extending approximately 90% across the circumference of a 2in pipeline was discovered and condensate had leaked from the pipeline and resulted in gas distribution. The actual leak rate is calculated to be around 8 kilogram/second. The volume of condensate from the leak is estimated to 4 cu m, Statoil said.
Although no personnel were injured, the investigation revealed that a gas leak of this size represents the potential of major incident if ignited and the outcome could have been fatal if anyone had been exposed to the leak.
“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,” Øystein Arvid Håland, senior vice president of safety and sustainability of development and production Norway said.
Level valve failure
In Statoil’s findings, the company discovered that based on material technical investigations, the crack was 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. The loss of valve control caused repeating powerful vibrations and strokes in the piping system, which exceeded the design capacity, Statoil said.
No material defects, metallurgical irregularities or welding defects have been proven. The investigation team believes that pure chance prevented a full pipeline break.
Gudrun’s 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, the company said.
“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 (PSAN) 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,” Bente Aleksandersen, senior vice president of the operations south cluster of development and production Norway said.
Just one day after the incident, the PSA launched an investigation into the early morning leak. Production was shut-in on the Gudrun platform and the facilities were depressurized.
At the time of the incident, 26 people were on board the facility and an additional 97 people were on board the nearby West Epsilon jackup.
Statoil is the operator of Gudrun field with a 51% interest. Partners include GDF Suez E&P Norge (25%) and OMV Norge (24%).
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