Alyeska pouring efforts into cold-weather ops
It has been a warm winter so far, and operators of the Trans-Alaska Pipeline System operators are thankful. But winter has just begun, and the worry of cold temperatures in Interior Alaska and a midwinter “event” that halts pipeline operations, like what happened in 2011, is never far from mind.
Since that suspenseful event when Alyeska Pipeline Service Co. engineers were concerned they couldn’t restart the pipeline, they have been aggressive about putting countermeasures in place.
It costs money, but heating the oil flowing through the pipeline has now become standard procedure.
Without the heating, oil could cool to 31 degrees Fahrenheit or lower by the time it reaches Valdez, at the pipeline’s southern terminus, a temperature at which ice formation and wax buildup would cause operational problems, Alyeska officials say.
The company operates TAPS on behalf of its owners, the large North Slope oil producers.
The problem is mainly is caused by the low volumes of oil as North Slope production has continued to decline. TAPS, completed in 1977, now operates at about 25 percent of its 2 million barrels-per-day design capacity, Admiral Thomas Barrett, Alyeska’s CEO, told an Alaska business group in a briefing.
“Our operations in winter are increasingly complex,” Barrett said.
At Prudhoe Bay, oil that once entered TAPS at its Pump Station 1 at 140 degrees Fahrenheit now comes in at 108 degrees. When the pipeline operated at full capacity of 2 million barrels per day it took four days for oil to reach Valdez, and with the pipeline full the friction of fluids moving against the pipe walls kept the oil warm.
Now it takes 15 days for oil to travel the 800 miles and because half the pipeline is built above ground there’s ample exposure to winter temperature that can reach minus-50 degrees. There isn’t enough oil flowing for the pipe wall-friction mechanism to do what it previously did.
“The real danger for us is if there is an unexpected winter shutdown. There could be significant problems,” if the oil were to congeal and ice were to form as water dropped out, Barrett said.
Exactly this happened in 2011 when a small oil leak at Pump Station 1 caused TAPS to shut down for several days during cold weather. At several points along the pipeline in Interior Alaska, the crude temperature dropped below freezing.
When regulators finally gave the OK, Alyeska was able to restart the pipeline, but with difficulty.
Pipeline operators are now adding heat at four locations by circulating the crude through loops of piping so that the friction adds heat. At Pump Stations 3, 4, 7 and 9, heat is added by running oil through recycle loop, at a rate of up to 25,000 barrels per hour at Pump Station 3.
Last January, oil left Pump Station One at a 106 degrees and an ambient sir temperature of minus-17 degrees. When the oil reached Pump Station 3, 100 miles south, its temperature had dropped 51 degrees.
Recirculating at Pump Station 3 added 15 degrees back.
The same process is repeated at Pump Stations 4 and 9, although at Pump Station 7, which has been shut down, a mainline pump has been kept active to do the recirculation.
In 2015, Alyeska added a new heat source, a diesel-fuel heating skid placed 17 miles north of Pump Station 7, at Remote Gate Valve 65, a point along the pipeline where cold winter temperatures are common and the pipeline could be vulnerable to ice formation.
Oil is extracted and circulated through a loop with about 2 degrees added by the heat skid. Alyeska is considering the addition of similar heat skids at various points.
TAPS also gets a bump in heat by the return of residual oil from a small refinery near Fairbanks owned by Petro Star Inc., an Alaskan refiner. Petro Star takes crude from TAPS and makes jet fuel and diesel, returning unused portions of the crude, at a high temperature, to the pipeline.
Michelle Egan, Alyeska’s spokeswoman, said the main strategy is to protect Pump Station 9, near Delta, southeast of Fairbanks, where the oil must be warmed enough to get the rest of the way to Valdez and over Thompson Pass in the Chugach Mountains.
“The higher winter production from the North Slope is a big help. On a lot of days now we’re moving 550,000 barrels per day, so the volume helps,” she said.
But throughput continues to decline at rates that have averages 5 percent a year and pipeline operators are concerned with wax buildup if rates reach 400,000 or 350,000 barrels per day, she said.
Meanwhile, one experiment tried by Alyeska has turned out to be unsuccessful. In a special test facility built at the University of Tulsa, the company experimented with a strategy of removing water from North Slope crude, from its ambient content of 0.2 percent water to 0.02 percent, to see of the crude could be run at temperatures below freezing without ice being formed.
Unfortunately, ice still formed even at the lower water content, Barrett said in his briefing.
“We learned we can’t flow it colder, so adding heat is now our main strategy,” Egan said.
Interestingly, the idea of circulating the crude oil through loops of pipe at pump stations to add heat was born in the crisis atmosphere of the 2011 early winter shutdown, when engineers were seriously worried that after several days the oil had cooled and gelled to the point that the system might not restart.
It wasn’t an immediate solution to the problem at hand but in a brainstorming session Alyeska’s engineers suggested it as a preventative measure for the future, and management adopted the plan.
The 2011 shutdown also brought some drama between state and federal regulators, and Alyeska’s management, over the restart. The Pump Station 1 leak was still being repaired but Alyeska asked for government permission to temporarily restart the pipeline flow to warm up the oil.
The U.S. Environmental Protection Agency, which had taken over control the federal agency management of the problem, refused, according to Dan Sullivan, now a U.S. Senator but who was state Commissioner of Natural Resources at the time. The state and Alyeska forcefully pressed the issue, warning EPA that the system could be down for weeks or even months with serious consequences to U.S. west coast oil supply and state of Alaska finances.
Sullivan said he was working back channel to the White House at the time, and EPA eventually backed down, allowing the temporary restart.
As Slope production continues its decline the point at which TAPS can no longer operate, as currently configured, is still unknown. Below 300,000 barrels per day, some form of “batch operation” could be implemented where the pipeline is operated periodically, drawing down oil stored at Prudhoe Bay.
Meanwhile, the steps Alyeska has to take is adding significant operating costs, a factor in the increasing tariffs for moving North Slope oil to Valdez.
“The real solution for us is finding more oil on the North Slope and adding new production and throughput,” Barrett said.
Although it would have been a decade away, new production from the Chukchi Sea from Shell’s exploration was being looked on by many Alaskans as a long-term savior for TAPS. Shell pulled out last fall, however, saying citing regulatory delays and costs amd disappointing results from the one exploration well completed this past summer.
Tim Bradner can be reached at [email protected].