Alyeska considering dry flow in TAPS

Alyeska Pipeline Service Co., operator of the trans-Alaska oil pipeline, is investigating the possibility of drying oil entering the line on the North Slope, to help resolve some of the emerging problems associated with low oil flow, as North Slope oil production declines, Tom Barrett, president of Alyeska, told the Alaska Senate Special Committee on TAPS Throughput on Feb. 5. With the temperature in the line now dropping below 32 degrees F at some points along the pipeline route during the winter, as the oil flow slows, the potential for water mixed with the oil freezing presents a growing threat to reliable line operation.

Alyeska has started to add heat to the oil by recirculating the oil at pipeline pump stations. But, eventually, adding heat will not be sufficient, Barrett told the committee.

“The operational challenges are complex, and just adding more heat will not solve the problems in this line,” Barrett said. “Right now we’re devoting significant resources to study and test what we call ‘cold dry flow’ … figuring out if we can remove water from the oil before it enters the pipeline … and run the line in a cold condition.”

As well as the possibility of ice formation, low oil flow also raises the specter of the increased deposition of wax from the oil, potentially clogging the line or obstructing “scraper pigs,” the devices sent down the inside of the line to clean the pipeline walls. Barrett said that on New Year’s Day a dense wax cloud had caused one of these pigs to become trapped at pump station 9, but that the pump station crew had succeeded in freeing the pig without any interruption to oil throughput.

—Alan Bailey