Statoil has concluded an internal investigation into a gas leak on one of its North Sea rigs.

During maintenance work on a pipeline, around 730 kg gas escaped from the Gullfaks B platform in one hour. The well was shutdown and the platform evacuated, with no injuries reported.

Now Statoil says that the December incident happened because a main hydraulic valve was inadvertently opened, allowing gas to leak out through the main manual valve into the well area.

The company has sent its report to Norway’s Petroleum Safety Authority.

Statoil executive Gunnar Nakken said today: “We took this incident most seriously. Our internal investigation report will be used actively in our improvement efforts. We have identified improvement areas within management, our competence and within technical areas. A dedicated project headed by the operative line has been set up to implement the necessary measures.”