Anchorage Daily News

Cleanup of a spill of oil, natural gas and water from a Prudhoe Bay pipeline continued Friday, state environmental officials said. They still didn't have an estimate of the spill size.

On Thursday they said the incident appears to have mostly involved release of natural gas. Among the liquids spilled, more of it was water than oil, they said.

The spill occurred Wednesday at Flow Station 2, a plant that separates oil from the natural gas and water that also come up a well at Prudhoe, the state's largest oil field. The 24-inch-diameter pipeline that leaked runs from Drill Site 9 -- a location of multiple oil wells -- to the flow station.

The accident has disrupted the flow of oil from Drill Site 9.

Initially 11 wells were shut down by BP Exploration (Alaska) Inc., which runs the field. BP later rerouted the flow from two wells to other pipelines. The nine wells still shut down as of Friday produced 922 barrels of oil a day. Prudhoe Bay-area fields normally produce about 370,000 barrels a day.

The state environmental officials say they think all of the spilled oil stayed on the flow station's gravel pad, with none escaping onto surrounding tundra.

Staying on the gravel makes the spill easier to clean up and less harmful to the environment.

BP has been troubled by oil spills at Prudhoe in recent years.

In March 2006 it discovered the largest spill ever at North Slope fields, some 201,000 gallons, due to a corroded pipeline.

Five months later another spill from a similar pipe caused the temporary closure of half of Prudhoe. In late 2007 BP pleaded guilty to a federal misdemeanor and paid $20 million in criminal penalties in the spills, which prosecutors said were the result of the company's knowing neglect of corroding pipelines.

BP runs Prudhoe on behalf of itself, Exxon Mobil, Conoco Phillips and Chevron.

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