Alaska Journal of Commerce
Alyeska Pipeline Service Co.’s president has warned that more frequent Trans-Alaska Pipeline System interruptions are likely as the pipeline company grapples with problems related to low throughput and increased maintenance needs.
Last January, TAPS was shut down for four days when a leak developed in a pump station pipe. Alyeska was able to restart the pipeline safely in winter conditions but had the restart been delayed two more days there could have been a prolonged shutdown that would have created a fuel emergency in Interior Alaska communities that depend on local refineries supplied by TAPS, Tom Barrett, Alyeska’s president, told a group of Anchorage business leaders.
“We will probably average 600,000 barrels per day this year, but as the decline in throughput continues we are at increasing risk of encountering operating problems,” Barrett said at meeting of the Resource Development Council, an Alaska-based resource advocacy group.
The pipeline has been in operation for 34 years now and has moved about 16 billion barrels since operations began in 1977. However, it now is operating at volumes below its original design parameters, Barrett said.
“This means we’re in unknown territory,” he said.
Those who designed TAPS in the 1970s did a good job, however. The pipeline withstood a magnitude 7.9 earthquake in 2002 with only minor damage and no spilled oil. The earthquake design parameter was 8.0, however, Barrett said.
Alyeska recently completed a two-year, $10 million study of low-flow issues that predicted water settlement problems will develop as throughput approaches 500,000 barrels per day; wax problems will develop as throughput nears 400,000 barrels per day and possible damage to the mainline pipe from frost heaves due to and lack of warm oil in the pipe and freezing soils, could occur at 300,000 barrels per day.
There is now ice flowing in the line in winter under present conditions, Barrett said. There are also problems with increasing vibrations that occur at low flow rates in certain topography, such as the down slopes from mountain passes.
As the decline continues the restart problems could be more serious with another midwinter interruption.
“If we have another winter shutdown there could be serious consequences for the state and our owner companies,” Barrett said.
More frequent scheduled maintenance shutdowns are likely also as Alyeska undertakes modifications on TAPS to deal with the issues. One example of a substantial modification that might be required is a new leak detection system to replace the existing system that may be less reliable with low volumes of oil flowing at slower speeds.
Alyeska is taking steps now to add more heat to the line, Barrett said. An expanded program of recirculating crude oil to warm it at two pump stations is planned for this year. The procedure warms the oil through friction as the crude recirculates through pipes at the pump stations. Tests are also planned with additional insulation added to the pipeline.
The problems develop through a combination of lower volume and lower velocity of the oil and the falling temperature of the moving crude oil, he said. Oil enters the pipeline at 105 degrees to 108 degrees F. on the North Slope but has typically cooled to about 40 degrees by the time it reaches Valdez.
It now takes 15 days for oil to move from the North Slope to Valdez, at the southern terminus of TAPS. At a 300,000 barrels per day throughput it will take 30 days.
North Slope fields are declining in production at rates of 5 percent to 6 percent a year.
“The decline has exceeded our projections and those of the state of Alaska,” Barrett said.
The solution, Barrett said, is increased production on the North Slope. If the TAPS throughput could be restored to 1 million barrels per day, all of the operating problems would vanish, he said.
Republished with the permission of the Alaska Journal of Commerce. Tim Bradner can be reached at firstname.lastname@example.org.