August 11, 2006
Pipeline May Have Been Corroded by Bacteria
Link: Bacteria Likely Cause of Pipeline Snafu. AP reports that BP suspects its pipelines leaked crude onto the tundra because oil-eatting bacteria produce an acid that corrodes the pipeline.
"That's our primary suspect at this moment. We'll know when we remove the pipe and have a good look at it," Craig Wiggs, a North Slope oil field manager, said on Friday as he led visitors on a tour of the Prudhoe Bay operations, a 333-square mile puzzle of pipelines and oil processing stations several miles from the bleak shores of the Arctic Ocean.
Early tests show that oil-eating bacteria may have caused the corrosion that caused the shutdown of much of the operation that supplies 8 percent of the nation's daily dose of oil.
Excrement from the microbe colonies inside the pipes produces an acid that eats through carbon steel designed to withstand temperatures that dip to 60 degrees below zero and oil that exits the ground at 160 degrees.
Telltale holes detected during ultrasound tests were most likely made by bacteria, rather than water, Wiggs said.
Sludge buildup on the inner walls of the pipe shelters the bacteria from anti-microbial fluids that oil companies are supposed to pour into the North Slope's zig-zagging network of pipeline 250 miles inside the rim of the Arctic Circle.
"That's what happens when you don't send cleaning pigs through," said Lois Epstein, who sits on a federal advisory committee for the Office of Pipeline Safety. Cleaning pigs are bullet-shaped scrapers released into the pipeline to slough off sludge and other solids.
A 210-gallon spill in one of the pipelines leading directly to the trans-Alaska pipeline led BP to announce earlier this week that it was shutting down its 400,000 barrel-a-day operation at Prudhoe Bay. The company was still deciding on Friday whether it could manage to keep half the field open.
Since then, the oil giant has been peppered with questions over why it hadn't detected the corrosion leading to this spill and another one in March. The spring spill ranks as the North Slope's largest, with up to 267,000 gallons leaked.
"None of this should have been a surprise to anyone related to the oil industry. It's made up of a lot of sophisticated people and the technology of internal corrosion is well-known throughout the industry," said Rick Kuprewicz, president of Accufact Inc., a pipeline energy consulting firm, based in Redmond, Wash.
BP workers with longtime history in the oil industry said they regretted the leaks that led to the shutdown.
"The fundamental objective of the oil and gas production operation is to keep the oil and gas inside the pipe and when we fail to do that it's a blow to those of us who are responsible for operating the field," said Prudhoe Bay field manager Kemp Copeland.
Bacteria can hitch a ride into the pipeline in the cold salt water that is sucked from the nearby Beaufort Sea and injected into the ground to coax the field's dwindling supply of oil up to the surface.
Oil, gas and water all exit the permafrost together and are separated out at flow stations scattered throughout the North Slope. In addition to seawater, the fresh water and natural gas are pumped back down to help maintain the underground pressure that pushes the hot oil to wellheads, which from a distance resemble red Christmas trees.
Microbes can enter any groundwater that is exposed to air before flowing back into the layer of gravel and sandstone 9,000 feet beneath the spongy tundra.
More and more water has come up from the ground as production rates have fallen from a 1989 high of 1.5 million barrels per day to 400,000 barrels before the shutdown. The water was most likely siphoned off before oil reached the rusted section of pipeline, but BP is looking into the possibility that some got by, according to Copeland.
"As the field has declined the water sitting underneath the oil has increased," Copeland said. "The ratio of water to oil coming out of the ground is higher."
The damaged transit pipelines are about 30 years old and sit above ground in wind-blown snow for most of the year, but Kuprewicz said neither factor should have been a problem.
"Just because pipe steel is old, doesn't mean that the useful life of the pipe is used up," he said. "Technically, pipeline steel doesn't age unless you're not paying attention."
The British oil giant runs and owns a 26 percent portion of Prudhoe Bay. ConocoPhillips and Exxon Mobil complete the triumverate with each owning a 36-percent share. Six smaller companies share the other 2 percent.
Of the 25 billion barrels of oil discovered in Prudhoe Bay in the late 1960s, more than 10 billion have flowed 800 miles south across three glacier-laced mountain ranges and more than 500 rivers, the Yukon included, to the port of Valdez. Three billion more barrels are thought to be recoverable.
"I find it incredible that fields of this magnitude would be shut down for this long," Kuprewicz said. "As engineers, there are various fixes to get by on without the nuclear option."
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