BP shutting down two North Slope pipelines; might need to be replaced

Two oil pipelines on Alaska’s North Slope are being shut down because of internal corrosion _ a worrisome problem that was the cause of a huge spill earlier this year in the aging Prudhoe Bay oil field.

One of the lines is a 24-inch diameter, 5-mile pipe at the Lisburne oil field. The other is a 14-inch diameter, nearly 4-mile line at Milne Point, BP PLC said Tuesday.

Together, the pipelines account for 22,000 barrels of the approximately 825,000 barrels that flows each day down the trans-Alaska pipeline to Valdez, where the crude is loaded onto tankers and taken to West Coast refineries. At Tuesday’s prices of $69.09 a barrel for Alaska crude, the shutdown means the loss of about $1.5 million a day.

The corrosion of the pipes comes as no surprise to BP, which runs the Lisburne line on behalf of itself and two other owners. BP is sole owner of the Milne line.

Both pipes had a history of corrosion and were being treated with corrosion inhibitor, said Maureen Johnson, a BP senior vice president. BP tried increasing the amount of corrosion inhibitor in the Lisburne line from 24 parts per million in 2002 to 200 parts per million in 2005.

It became increasingly apparent corrosion inhibitor was not doing the trick.

The line was not producing a continuous flow. An X-ray of the pipe showed internal corrosion in an arrow shape, indicating the damage was being aided by the velocity of fluid moving through the pipe, Johnson said.

``We started to conclude last year that corrosion inhibitor alone might not stop this problem,’’ she said.

The problem with the Milne oil field line is similar, she said. The corrosion is being caused by carbon dioxide in the lines, a problem BP and other North Slope operators have been aware of since Prudhoe Bay began production in June 1977.

BP is leaning toward replacing both pipelines, Johnson said. The earliest that work could be done would be in 2007.

—The Associated Press