Unocal's Dillon oil and gas production platform in Cook Inlet was shut down for about 12 hours Tuesday after a cracked fitting leaking crude oil was discovered.
"The worst case scenario is 55 barrels," said Unocal spokesperson Kevin Tabler in Anchorage. "That sounds like a lot, but that's the maximum that could have been lost. It was something less, but how much, I can't tell you."
He said that figure was calculated based on the estimated rate of leakage, the size of the crack, line pressure and the maximum length of time the pipe could have been leaking.
He said very little in the way of oil was recovered by Cook Inlet Spill Prevention and Response Inc., which sent the response vessels SeaBulk Montana, Monarch and a 249-barrel oil barge to the scene.
Leslie Pearson, a spokesperson for the Alaska Department of Environmental Conservation in Anchorage, said it's possible that the light Cook Inlet crude oil could have atomized and evaporated because it was sprayed out at high pressure.
"That's entirely possible," Tabler said. "Envision a garden hose with your finger over it."
The spill was reported at 2:47 a.m., and Pearson said a predawn overflight with an infrared camera spotted a 50-by 300-foot oil sheen as far as eight miles south of the platform on the outgoing tide.
"It's what we would call a 'sheen' because it was so thin," she said. "Usually those are hard to recover."
By sunup, no sheen was visible.
The lightness of the crude and the rip tides in Cook Inlet probably worked together to dissipate the spill quickly, Pearson said.
"The oil probably got in one of those rips and was just ground up," she said.
The U.S. Coast Guard reported that an analysis by the National Oceanic and Atmospheric Administration indicated the spill would break up in central Cook Inlet and would not affect the shore or any wildlife.
The leak was discovered on a routine inspection of the platform at 2:30 a.m. There is an auto-shutoff on the power oil system, but the leak was not big enough to trip it because the pressure did not drop far enough, Tabler said. The power oil system uses a high-pressure pump to re-inject crude oil back into the well.
"The longest time between inspections was 110 minutes between the time he read the gauges and came back," Tabler said. "It was discovered during the normal course of operations. That's why we do the inspections. The system works."
Unocal engineers were finishing the repairs and doing more preventative screening, Tabler said. He expected the platform to be up and running again by late Tuesday afternoon.
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