Image courtesy of © BP p.l.c.
As any cook who’s poured grease down the drain can tell you, slow-moving oil clogs pipes. But this household fact was not foremost on the minds of the engineers and oilmen who rejoiced when the crude first started to flow on the Trans-Alaskan Pipeline in 1977. Arguably one of the greatest engineering—and political—feats of the 20th century, the pipeline was built for fast-gushing oil and the chief challenge that faced its engineers was how to deal with the massive quantity.
Now that the oil field in Prudhoe Bay, as well as others in the far northern environs, are down to the last few swigs, the problems of low flow are becoming apparent. At its peak in 1988, the pipeline delivered some two million barrels a day, a good 25% of the nation’s oil. With that kind of current, it took a mere four days for oil to make the 800-mile journey from pumps in the north to the Port of Valdez in the south. The speed meant that the oil traveled at a comfortably fluid 100 degrees. But with barrels per day now down to 600,000, the trip takes a full two weeks, and if production goes down to 500,000 barrels, it will take 18 days; at 300,000 barrels, it’s a month-long trip. Slower oil means colder oil and it now flows at a dangerous 40 degrees. Colder temperatures means potential clogging, and it gives water a chance to separate from the oil and form ice.
Colder temperatures allow water to separate from the oil, forming ice which leads to clogging.
One solution would be to fill the pipeline with more oil, an act which would require more drilling. This is deemed the only long-term viable solution by the pipeline’s owner, Alyeska Pipeline Service Company, Anchorage, AK. Alyeska is owned by global energy firms BP, ConocoPhillips, ExxonMobil, Unocal, and Koch. As it is, the pipeline’s output is no dribble. It continues to satisfy 12% of U.S. oil consumption, earning plenty for its owners and lubricating the Alaskan economy. With a little ingenuity, the short-term may not be so dire—or so short.
“We do believe that there are things we can do immediately, and in the next year, and in 20 years, so that it can operate as input levels continue to decline,” says Katie Pesznecker, Alyeska’s community and public relations manager.
In January of this year, Alyeska got a taste of the dangers of cold oil. A leak forced the pipeline to shut down for six days and temperatures dropped to near-congealing levels. To keep things liquid, they pumped oil that had been warmed at refineries back in to the pipeline. The technique was so effective that it is soon to become a part of regular operations.
Subsequently, the company produced a “Low Flow Study.” In addition to recycling warmed oil, the paper recommends adding external insulation to pipe segments in the coldest regions. A third, and more costly, solution would be to install heaters along the pipeline. The company is about to test a “heat trace installation,” with wires applied to the exterior of pipes and heated with generators. This would only be used at critical low flow points. “The requirement of high voltage power line-wide does not currently exist and is cost prohibitive to construct,” says Alyeska Project Manager, Amy Stoodt. “There is not a single technology that can be implemented—it will take a comprehensive set of projects to provide the solutions to TAPS' viability.”
The machines known as pigs, similar to the one shown here, are used to clean debris within the pipeline. Image courtesy of Alyeska Pipeline.
To keep the arteries free of clogs and ice, Alyeska increased the frequency of its pigging program in which machines, known as pigs, travel through the pipeline and inspect and scrape the interior walls.
Exactly how long such techniques can keep the pipeline up and running—and profitable—and what happens afterward, is anyone’s guess. Says Pesznecker: “I haven’t heard of that discussion ever being had.”
Michael Abrams is an independent writer.