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TAPS already hitting low flow issues Alyeska president warns that without increased North Slope oil production the pipeline to Valdez runs the risk of a major outage Alan Bailey & Kristen Nelson Petroleum News
In February Alyeska Pipeline Service Co. President Tom Barrett told the Alaska House Resources Committee that the trans-Alaska oil pipeline system, known as TAPS, had come close to the brink of a major outage when forced into a winter shutdown following an oil leak in January at pump station one, at the northern terminus of the line.
And on March 18 Barrett was back in Juneau talking to the House Finance Committee, reiterating his concerns about declining oil flow through the line and saying that the pipeline is already at a point where cooling of the slowly flowing oil as it travels from Prudhoe Bay to Valdez could lead to a major disruption in pipeline operations.
“A lot of people have asked me, at what point will the declining flow of crude oil become a problem for TAPS, for Alyeska,” Barrett said. “And the response is simple — the problem exists out there now. This is not something facing us down the road; it’s not theoretical; it’s an issue we confront at TAPS daily, today. And without increased throughput in the line, our challenges of operating the line safely will increase over time.”
Designed for more oil The problem is that the 48-inch pipeline was originally designed to carry much more oil than the 630,000 barrels per day that currently flows into the line from Pump Station 1. As a consequence, the length of time that it takes each barrel of oil to travel from the North Slope to Valdez has increased from four-and-a-half days during peak throughput in the late 1980s to about 15 days now. The increasing travel time causes the oil to cool more and more as it flows south during the cold of the winter, thus raising the risk of water that is carried with the oil freezing, and increasing the potential for wax and sediments to drop out of the oil and clog the line.
The coldest point of the line is the section near where the line crosses the Yukon River. Then, at a point just east of Fairbanks, to the south of the Yukon, the North Pole oil refinery takes some oil from the line and then returns unneeded refinery products into the line, thus warming up the oil for the second half of the 800-mile trip to Valdez.
During the response to the January oil spill, with the oil temperature hovering around 36 F in the Yukon section of the line, Alyeska had to temporarily restart the line while oil was still leaking, to prevent a freeze up in the line during the time taken to assemble the resources required to fix the leak. The restart also enabled the recovery from the line of two devices called pigs that might otherwise have become frozen in place.
The longer the pipeline is shut in during the winter, the more difficult the subsequent startup becomes, Barrett told the legislators. And one of the biggest risks is ice or wax damage to one of the mainline pumps, a catastrophe that could result in a pipeline outage lasting several months, he said.
Major impact An extended pipeline shutdown would obviously lead to a shut in of North Slope oil fields. And, apart from the consequent economic impacts of this happening, the shutting in of oil wells over an extended period of time could lead to irreversible well damage. And then there is the question of impacts on the North Pole refinery of an extended loss of crude oil feedstock — the refinery supplies heating fuel for Interior Alaska as well as jet fuel for Anchorage International Airport.
Were the refinery itself to go out of business, regardless of any shutdown of pipeline operations, that would cause a major operational problem for Alyeska because of the continuing need to warm up the oil at North Pole, Barrett added.
“We would have to find a way to add heat in some other manner,” he said.
In 2007 Alyeska launched a study into the consequences of low oil flow and how to deal with those consequences, but the company has discovered, both through the study and through the lessons learned from the January oil spill incident, that the low-flow issue is more complex than originally envisaged, Barrett said. One problem, for example, is that the instrumented pigs — the devices that Alyeska periodically sends down the line to monitor pipeline wall corrosion — are not designed to operate at the low travel speeds that oil flow in the line is heading for. And, at the same time, Alyeska’s sophisticated pipeline leak detection system was also not designed to operate at very low flow rates. At some point Alyeska will need to upgrade its leak detection system, at great expense, if oil flow continues to drop, Barrett said.
Increasing risk Barrett emphasized that there is no specific threshold throughput volume below which the pipeline will cease to operate. Rather, the declining throughput volumes progressively increase the risk of pipeline throughput disruption.
“Depending on which engineering group you’re talking to, anywhere from 500,000 barrels a day to 300,000 barrels a day becomes increasingly problematic,” Barrett said. “I am uncomfortable at 640,000 barrels because of the (January) scenario we just went through.”
As a consequence of its low-flow study, Alyeska has developed some techniques to address the problem of the cooling oil. For example, during the January incident Alyeska warmed the oil close to the halfway point of the pipeline route by recirculating oil in Pump Station 7, a pump station that is no longer in active use for pumping oil through the line, Barrett said.
Other future possibilities include the use of oil heaters or the installation of heating tape on the pipeline, or the use of heat recovered from turbine exhaust gases at pump stations.
Ultimately, the solution to the low flow problems is to produce more oil for pumping down the pipeline, with throughput really needing to be above 800,000 barrels per day and preferably as high as 1 million barrels per day, Barrett said. But while oil production in the United States as a whole went up in 2010, Alaska production declined in that same time, he said.
“At the end, our bottom line is pretty simple and straightforward: We need more oil in the pipeline,” Barrett said. “TAPS viability, in all honesty, depends on the political will for oil development; it depends on it in Washington and it depends on it in Alaska. And so we need help to get safe and responsible production in Alaska; it’s urgent and it’s critical.”
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