Pipeline at 40: 'Cold War' against lower flow
More than 2-million barrels of oil used to flow through the Trans Alaska Pipeline, daily. As the pipeline reaches its 40th anniversary, that rate has dropped to about one-fourth of its peak in 1988.
This decrease in pipeline oil is causing major problems for engineers and pipeline operators.
“It's a big deal for us,” said Betsy Haines, the senior engineering director for Alyeska Pipeline. “The slower it goes, the more difficult and complex the problem is. And so that's what we're working on right now.”
North Slope crude oil has a temperature of about 100 degrees, when it comes out of the ground. And in years past, the oil stayed close to that temperature all the way down to the end of the line, in Valdez.
Now, with less oil flow, the oil cools down much faster, especially during winter, and its temperature can dip below 40 degrees.
When that happens, wax and water, which are in the oil when it’s pumped out of the ground, can collect within the pipeline. Moreover, the wax, which used to remain melted, can now collect along the pipeline walls.
Company officials say the problem has grown worse, through the years.
Water, which also naturally occurs in the oil, can settle and cause corrosion, or turn to ice. This hampers the operation of critically important safety values.
Alyeska Pipeline says it has taken steps to combat the problems caused by lower oil flow, and the company is studying potential improvements for the future.
Since the pipeline began operating, devices called “pigs” have been inserted into the line to clear wax, but the operation has become far more complicated in recent years. Pigging is done more frequently, because of the wax problem.
“It's a very dirty job to begin with,” said Wes Willson, operations and maintenance supervisor at Pump Station 9, near Delta Junction. “Our last pig that we had we recovered had nine barrels of wax. That's about 16-hundred pounds, and that's fairly typical.”
To try to keep the oil warmer, a portion of the oil is now removed and recirculated at four pump stations to boost the temperature. Two portable heating units are also put into service, during winter.
A special team of engineers is now studying the low-flow problem, and they are using a newly developed camera system to see the oil flowing in the pipeline and study microscopic particles of wax and water mixed with the oil.
“This is critical. This is the first time we've ever had a chance to see what's going on inside the pipeline,” said engineer Jacques Thibeault. “Up until this point, all of our studies and analysis have been through modeling in flow loops, which have been conducted in a very controlled, laboratory environment.”
Pipeline managers are confident that they can overcome the technical challenges caused by lower oil flow.
“I think some of the technical challenges right now that we face are as challenging as some of the technical challenges that engineers faced in the very beginning,” said Rod Hanson, senior vice president for operations and maintenance.