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King Salmon platform back in operation Unocal looks elsewhere for cause of sheen after successful hydrotest of oil line Sept. 15 Kristen Nelson PNA Editor-in-Chief
The Alaska Department of Environmental Conservation said Sept. 18 that Unocal's King Salmon platform in Cook Inlet is back in operation. Unocal spokeswoman Roxanne Sinz told PNA that the platform oil pipeline was started up again Sept.15 after a hydrotest.
Unocal had responded to a sheen in the vicinity of the McArthur River field platform by shutting in the platform and hydrotesting an 8-inch subsea crude oil pipeline which carries oil from the platform to the Trading Bay production facility on the west side of Cook Inlet. There is also an 8-inch natural gas line connecting the platform to the shore.
DEC said Sept. 13 that droplets of oil had been observed adjacent to the platform for about two weeks, but the source had been believed to be equipment on the platform. The afternoon of Sept. 12, however, it was determined that the source was subsea.
The amount and type of oil are unknown. DEC said it appears to be bubbling up from a subsea source adjacent to the platform on an intermittent basis. The bubbling is underneath the flare boom, but the source appears to be beneath the water surface. The oil bubbling was observed at 10:20 Sept. 13 and appeared to stop 50 minutes later, producing a sheen approximately 20 feet by 400 yards.
Production suspended Sinz told PNA Sept. 13 that the sheen is very small and is just north of the platform. It was spotted at 10:20 a.m. Sept. 13 and Unocal began work to shut in the platform and planned to begin hydrotesting the oil line that same day.
On Sept. 14, Sinz told PNA, there was another small sheen in the vicinity of the platform. The oil line had been displaced with water and Unocal was preparing for a second displacement, which would be followed by a hydrotest. She said the source was still unknown, the quantity was still unknown and Unocal was continuing to investigate.
DEC said the crude line was hydrotested in February as a precautionary measure following the Dolly Varden platform leak from an 8-inch subsea crude oil pipeline and there were no anomalies noted in the King Salmon pipeline in the February testing.
Crude line hydrotest successful DEC said Sept. 18 that a successful hydrotest on the crude oil pipeline was completed Sept. 15, the pipeline was deemed fit for service and the Unocal returned the platform to production after consultations with DEC and the U.S. Coast Guard. The natural gas pipeline was ruled out as a source of the sheen because, DEC said, sheening could occur only if there were condensate liquids in the pipeline and that is very unlikely since the pipeline is used to bring high quality dry fuel gas to the platform for engine fuel. In addition, the agency said, at the current operating pressure of 400 psi, gas bubbles would be present with the sheen.
DEC said the sheen is an unknown oil type, although initial sample analysis indicates that the product is similar to a No. 4 diesel. Oil still appears to be bubbling up from a subsea source adjacent to the platform on an intermittent basis.
Cook Inlet Spill Prevention and Response Inc. response vessel Seabulk Montana has been activated and positioned at the platform during low slack tides, which is when the sheens have generally been visible. The CISPRI crews are recovering oil using sorbant sweep when possible and are also collecting samples.
DEC said that Unocal has provided DEC and the Coast Guard a list of 20 possible sheen sources in addition to detailed plans for investigating each potential source until the source is determined. A side-scan sonar survey of the seafloor at the platform was scheduled for Sept. 18.
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