NOW READ OUR ARTICLES IN 40 DIFFERENT LANGUAGES.
HOME PAGE SUBSCRIPTIONS, Print Editions, Newsletter PRODUCTS READ THE PETROLEUM NEWS ARCHIVE! ADVERTISING INFORMATION EVENTS PETROLEUM NEWS BAKKEN MINING NEWS

Vol. 16, No. 9 Week of February 27, 2011
Providing coverage of Alaska and northern Canada's oil and gas industry

Jan. shutdown puts TAPS close to brink

Click here to go directly to this story within the full PDF version of this issue, with any maps, photos or other artwork that appears in some of the articles.

Email it to an associate.

Alyeska executives describe efforts to prevent freezing in pipeline after pump station oil leak in era of low oil throughput

Alan Bailey

Petroleum News

In many ways the central artery of the Alaska economy, the trans-Alaska pipeline carries about 11 percent of U.S. domestic crude oil production. But a shutdown of the pipeline in January following an oil leak at Pump Station 1 on the North Slope dramatically illustrated the growing risk of a major pipeline outage, as declining pipeline throughput allows the temperatures of the fluids flowing down the line to drop to lower and lower levels in the winter.

“I was closer to the edge of the cliff that I didn’t want to go over, and I don’t think Alaskans want to go over,” Tom Barrett, president and CEO of Alyeska Pipeline Service Co., told the Alaska House Resources Committee on Feb. 17 when recounting how an army of Alyeska employees and contractors had swung into action, preventing water from freezing in the line following the Jan. 8 oil spill incident. Alyeska operates the pipeline on behalf of the pipeline owners.

Declining throughput

The essential problem that Alyeska faces is that, with pipeline throughput declining from a peak of about 2.1 million barrels per day in 1988 to 630,000 barrels per day recently, it now takes 15 days for the oil to travel from the North Slope to the tanker terminal in Valdez. The oil cools as it travels down the line, with the potential for water in the oil to freeze out as ice, blocking the movement of pigs — the devices used to scrape clean the inside walls of the line — and potentially damaging valves and other pipeline equipment.

When the leak was discovered in a booster pump building at the northern end of the pipeline on Jan. 8, Alyeska promptly shut the entire pipeline down while personnel investigated what had happened and formulated a plan to deal with the situation.

But at the time of the shutdown the oil temperature was just 36 F in a section of the pipeline known as “the bowl,” in the area of the Yukon River, Alyeska Oil Movements Director Betsy Haines told the committee. And with one pig in the line in the bowl section and another in the line near Glennallen, there was a real risk of one of those pigs becoming frozen in place, thus causing a huge problem in restarting the line.

Immediate response

Realizing the urgency of the situation and recognizing that unpredictable and changing weather conditions could impact the response effort, Alyeska put a major response into action as quickly as possible, Barrett said.

“You move immediately as far and as fast as you can,” he said. “If you get behind on the response curve you may never be able to catch up.”

Normally Alyeska carries out pipeline shutdowns in the summer, when the oil in the line remains relatively warm. And the company plans those shutdowns in detail, months in advance, rather than at a moment’s notice.

On this occasion, with an almost immediate cessation of flow through the line and with oil continuing to flow into storage tanks at Pump Station 1, the company made an emergency request to the North Slope producers to cut total production back to 32,000 barrels per day, just 5 percent of the regular flow rate.

Need for restart

Alyeska has for several years been studying the impact of declining pipeline flow rates and devising ways of dealing with low-flow problems. Using data from these low-flow studies, a company engineer determined that, despite the unresolved oil leak, the pipeline needed to be restarted to prevent ice formation in the line and to enable recovery of the two pigs, Haines said.

The situation became one of balancing risks, the risk of damage from the oil spill versus the potentially catastrophic consequences of a pipeline freeze-up, Barrett explained, saying that he decided that a restart was essential, despite the fact that restarting a line with an oil leak “ran across the DNA” of every pipeline regulator.

“That was actually from my perspective … the most prudent course of action for us to take,” Barrett said, commenting that he was also concerned about the possible impact of weather-related delays in moving all of the necessary equipment and materials to Prudhoe Bay, were the pipeline to remain shut in.

Following the preparation and checking of safe restart procedures, oil started flowing down the line again on Jan. 11, with vacuum trucks sucking leaking oil from the booster pump building.

By that time, with much of the North Slope field production already having been shut in, the producers could only restore total production to about 400,000 barrels per day, a volume not high enough to eliminate the risk of a freeze-up, Haines said. Alyeska put into operation one of the techniques designed from its low-flow studies, the cycling of oil at some of the pump stations to keep the oil warm, she said.

Pigs recovered

In the event, the Alyeska team, in operation around the clock along the entire length of the line, managed to recover both of the pigs from the line, as oil slowly flowed again, thus averting the possibility of a stuck pig, the biggest freeze-up concern.

And about four days after the temporary startup, with all the necessary equipment, materials and personnel on site at Pump Station 1, Alyeska shut the pipeline down again, to install piping to bypass the pump building oil leak. By then, with a change in the weather causing temperatures to plummet, welders and other personnel worked around the clock, completing the repairs and allowing the pipeline to restart after two days.

“We had people working at 20 below inside buildings at Prudhoe Bay,” Barrett said.

By the time that the pipeline restarted after the repairs, the oil temperature in the bowl area of the line was down to around 28 F, Haines said. And, with the producers unable to fully restore oil throughput immediately, it was 15 to 18 days before fresh oil moved fully through the system, she said.

Safety is paramount

Saying that personnel safety had been the top priority and that there had been no identifiable environmental harm from the oil leak incident, Barrett slammed any criticism of the length of time that it had taken Alyeska to bring the trans-Alaska pipeline back into operation.

“I’m not getting anyone hurt bringing this line back up,” he said.

At the same time, the experience of dealing with a forced winter pipeline shutdown has re-enforced concerns about winter operation of the pipeline, as pipeline throughput continues to drop. There a number of possible scenarios that could force another winter shutdown in the future, with some of these scenarios not involving a fault in the pipeline itself, Barrett said.

And, although Alyeska continues to seek ways of dealing with low oil flow, the best solution to the low temperature problems is to pump more oil through the line, a prospect that seems improbable over the next five to 10 years, he said.

“It’s declining flow and it’s not looking good to me,” Barrett said.



Did you find this article interesting?
Tweet it
TwitThis
Digg it
Digg

Submit it to another favorite Social Site or Article Directory.

del.icio.us Facebook Furl Mixx NewsVine Reddit StumbleUpon YahooMyWeb Google LinkedIn Live MySpace Sphinn Technorati Yahoo! Buzz
Print this story | Email it to an associate.






Petroleum News - Phone: 1-907 522-9469 - Fax: 1-907 522-9583
[email protected] --- http://www.petroleumnews.com ---
S U B S C R I B E

Copyright Petroleum Newspapers of Alaska, LLC (Petroleum News)(PNA)©2013 All rights reserved. The content of this article and web site may not be copied, replaced, distributed, published, displayed or transferred in any form or by any means except with the prior written permission of Petroleum Newspapers of Alaska, LLC (Petroleum News)(PNA). Copyright infringement is a violation of federal law subject to criminal and civil penalties.

This story has 101 lines. and it is 3155 pixels high.