The Norwegian Petroleum Safety Authority issued Statoil with the order for the May 26, 2012, incident. The PSA said a leak, "among the most serious gas discharges on the Norwegian shelf," was likely caused by a problem with emergency shutoff valves at an offshore platform.
The PSA said it decided to issue the order to Statoil after conducting an investigation into the incident.
"According to operator Statoil's own calculations, the leak on Heimdal caused the emission of 3,500 kilograms of gas over a period of 252 seconds with an initial rate of 16.9 kg/s. The total gas volume in the piping segment was 7,000 kg," the PSA stated.
Statoil has until March 1 to identify the causes of the accident, present a plan to ensure improvement measures have been implemented and confirm there are no similar conditions at the facility.
Statoil in May said it began its investigation after testing of emergency valves caused the incident. No injuries were reported among the 98 people on the platform at the time. The company said workers were able to return to the platform the same day.