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Alyeska working to add heat to crude oil Cold winter weather in Interior Alaska compounds challenges of keeping smaller, slower moving volumes of oil moving through TAPS TIM BRADNER For Petroleum News
Interior Alaska is having one of its coldest winters in years and Alyeska Pipeline Service Co. is adding all the heat it can to crude oil flowing through the Trans Alaska Pipeline System.
Temperatures recently dropped to minus 50 and minus 60 Fahrenheit at some points in Interior Alaska, which the 800-mile pipeline crosses in moving oil from the North Slope to the TAPS marine terminal at Valdez
“We’re adding all the heat we can,” Alyeska President Admiral Thomas Barrett said.
Alyeska spokeswoman Michelle Egan said the problem is exacerbated by the low volumes of oil moving through the pipeline. TAPS was built to handle 2 million barrels per day but is now moving just over 500,000 bpd. The lower flow means oil takes much longer to travel 800 miles to Valdez, and is more exposed to cold weather in winter.
Oil recirculated Heat is being added this winter by recirculating crude oil at TAPS Pump Stations 3 and 4 on the North Slope as well as stations 7 and 9 in the Interior, Egan said, with additional heat added with mobile heating units installed at a remote gate valve, RGV 65, and at a closed pump station, Pump Station 8, which is near Fairbanks in the Interior. In recirculating, Alyeska re-pumps oil through loops so that the friction adds heat.
Alyeska’s challenge is to keep the oil warm enough as it moves through spots of the Alaska Interior where there is intense cold, such as low points in river valleys, Alyeska has said in the past.
Crude oil won’t start to jell until it is below 32 degrees Fahrenheit, the freezing point for water, but at that temperature ice can also form in the line as water drops out of the crude oil, causing problems. Also, wax accumulations cause other issues.
Alyeska’s goal is to keep the temperature well above freezing so there is a margin of safety in case an operations problem requires a temporary shutdown. This happened a few years ago in mid-winter and at the time Alyeska was very concerned about getting the pipeline restarted. It was able to do that, but the winter conditions were mild that year. This winter has been different. Temperatures were measured on day at minus 58 degrees Fahrenheit at Pump Station 5, Egan said.
Oil starts at 105-110 degrees Crude oil is now entering TAPS at Pump Station 1, at Prudhoe Bay, at about 105 to 110 degrees Fahrenheit, but the temperature drops rapidly as the oil moves south through sections of the pipeline that are built aboveground.
Egan said that on one recent cold day the temperature dropped to 57 degrees F by the time oil had travelled 100 miles to Pump Station 3, in the southern North Slope. At that point, recirculation added 13 degrees of heat back into the crude, she said.
Similar steps are taken as the crude moves south and cools, and is then reheated. “We’re using all the methods we have to maintain temperatures,” Egan said.
Barrett said a major concern for Alyeska is the potential for an operational problem with the remote heating systems that would require the pipeline company to put people into the field in very cold weather.
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