The hydrocarbon leak occurred while stabilised oil was being transferred from Statfjord A to Statfjord C.
At the same time, preparations were being made for maintenance work on a loading pump in the shaft. An isolation valve for the pump sprang a leak, causing the pump house to fill with oil. This oil drained to the sump tank at the base of the shaft via an open drain valve. When the level in the sump tank reached 70 per cent, the pump for transferring liquid from the sump tank to the oily water tank beneath the cellar deck started up. The valve controlling the level in the oily water tank failed to open, and oil escaped via fire seals on the cellar deck.
Statoil calculated that up to 42 cubic metres of stabilised oil escaped in about 37 minutes, at a leak rate of 20.8 kilograms per second. Forty cubic metres are estimated to have spilt to the sea, while two cubic metres dispersed over the installation.
There were 270 people on the installation, and no personal injuries have been reported as a result of the incident. Production was shut down for almost four days owing to the leak.
Potential consequences in the event of ignition are assessed to be a possible spray fire or combustion of oil drops/flowing oil for the duration of the leak.
In addition, the probability for a repetition of similar leaks was high immediately after the incident.
The PSA resolved to investigate the incident. Read more: Statfjord C hydrocarbon leak to be investigated
Six nonconformities were identified by the investigation. These related to:
- the original design solution for the drainage system
- the modified design solution for the drainage system
- consequence classification of the open drainage system
- preparations for maintenance
- management of simultaneous activities
- qualification and follow-up of contractor expertise.
Four improvement points were also identified. These include critical comments from the PSA concerning parts of Statoil’s own investigation concerning classification of the leak, its potential consequences and a failure to address the underlying causes of the incident adequately.
On the basis of the findings of its investigation, the PSA has given Statoil the following order:
Pursuant to section 69 of the framework regulations on administrative decisions, see section 21 of the management regulations on follow-up, Statoil is ordered to review its system for following up and identifying the reasons why the technical, operational and organisational weaknesses, faults and deficiencies which have been identified, see chapter 6.1 of the report, have not been identified, and to implement the necessary measures.
The deadline for compliance with the order is 1 October 2014.