Statoil ASA (STO) said May 20 that its corporate investigation team completed the investigation of the Feb. 18 condensate leak on the Gudrun platform in the North Sea.

On Feb. 18, hydrocarbons were found in the platform’s process module after reports of noise and vibrations.

Condensate had leaked through a 2 mm-wide crack that ran about 90% of the circumference of a 2-in. pipeline. Condensate leaked out at about 8kg/second, and Statoil said the volume was estimated at 4cu.m.

During the incident, no one was injured, and there were no personnel in the area. Statoil said the investigation concluded that the outcome could have been fatal if people had been exposed to the leak, because a gas leak of this size has major incident potential if ignited.

Based on material technical investigations, the crack in the pipeline resulted from 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.

No material defects, metallurgical irregularities or welding defects were proven, and investigators think it was simply chance that the pipeline did not fully break.

The 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.

Bente Aleksandersen, senior vice president of the operations south cluster of Development and Production Norway, said the investigation provided valuable information that Statoil, the Petroleum Safety Authority Norway, and others in industry could use to prevent incident recurrence.

Offshore