Between 60 and 70 cubic metres of crude leaked into the sea from a flash tank for produced water on the Åsgard B platform in the Norwegian Sea in the early hours of 30 September.
The leak was discovered in the morning of 30 September and production from the platform was consequently stopped until the same afternoon.
Svein F Fredriksen, technical operations manager on Åsgard B, reports that the platform has now resumed normal production and is exporting roughly 26 million cubic metres of gas per day.
According to Mr Fredriksen, the leak originated in closed valves on the water outlet from the Smørbukk oil separator. The crude got into the flash tank for produced water and then leaked into the sea along with the water The crude will gradually be broken down and will not reach the shore, but the film of oil on the sea is being monitored.
The Norwegian Pollution Control Authority (SFT) has been notified in accordance with normal procedure.
Statoil is setting up an internal commission of inquiry to investigate the cause of the incident.
The processing plant on the Åsgard B platform handles the wellstreams from the Midgard gas deposit and the Smørbukk deposit, which contains oil, gas and condensate.
Mr Fredriksen says that preparations to start Smørbukk up are already underway, but the oil separator has not yet been restarted.