NPD Completes Investigation into Draugen Platform Leak

The Norwegian Petroleum Directorate (NPD), the Norwegian Coastal Directorate and the Norwegian Pollution Control Authority (SFT) have now completed their investigation of the oil leak that took place on the Draugen field on May 19th of this year in which approximately 750 m3 of oil leaked into the sea.

The NPD has notified the operating company Shell that it will issue orders relating to quality assurance and follow-up of suppliers, as well as procedures for start-up and operation of subsea installations.

The notification of order also requires that Shell perform a review of its documentation concerning emergency preparedness on Draugen to ensure that necessary measures are implemented, as well as to ensure that responsibilities and training are clearly described. The Norwegian Coastal Directorate and SFT have not determined how they will react in relation to this incident.

The oil leak occurred during start-up of the subsea installation Garn West at 1700 hours on 19 May. The subsea installation had then been shut down for 19 days due to maintenance work. The leak was discovered at about 2230 hours when the crew on board the Draugen platform noticed an odor and observed oil on the surface of the sea around the installation. Oil production on Draugen was shut down shortly thereafter.

The cause of the oil leak was a crack in the end-fitting between the Garn West subsea installation and the pipeline which carries oil from Garn West to the Draugen platform. The crack in the end-fitting occurred because the material the pipeline is made of became brittle due to exposure to excessive stress, while hydrogen was also present at the site of the rupture (stress corrosion).

The system is exposed to considerable tension, and this was not sufficiently addressed in connection with the engineering work. Therefore, the load became greater than assumed. Moreover, the end-fitting did not have a surface treatment that protected it against hydrogen penetration.

The cracking occurred during the maintenance shutdown, and Norske Shell had indications of a pressure build-up in the pipeline prior to start-up. The increase in pressure was relatively small, and the cause was not investigated prior to start-up of production.

After the leak was discovered, Shell mobilized its emergency response organization for acute pollution. Among the efforts instituted was collection of the spilled oil and about 180 m3 of oil was recovered in the days that followed. The coastline in the relevant section of Mid-Norway was monitored, but no oil reached land. Observations have shown no harm to birds or fish.

Collection of the oil on the sea did not get underway until 12 hours after the leak was discovered. In the investigation report, the NPD, the SFT and the Norwegian Coastal Directorate point out that the collection of the oil should have gotten underway earlier. The response time for collection - stipulated in the SFT's decision in connection with establishment of area emergency preparedness on Haltenbanken - is five hours. The Draugen leak on May 19th is the third largest oil leak to occur on the Norwegian shelf. The largest leak occurred on Ekofisk Bravo in connection with the blow-out in April 1977 when about 12,700 m3 of crude oil leaked out during the course of the week the blow-out lasted. In 1992, there was an oil spill of 900 m3 on the Statfjord field as a result of a valve on a hose to a loading buoy accidentally being left in the open position.

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