North Slope spill report focuses on flow lines

Posted: Friday, December 03, 2010

ANCHORAGE - A new state report on Alaska North Slope petroleum spills concludes the flow lines moving crude oil, water and natural gas from wells to processing plants need heightened monitoring.

The report by the state Department of Environmental Conservation reviewed aging infrastructure used to extract and process oil that eventually moves through the trans-Alaska pipeline, which offloaded its first barrel in Port Valdez in 1977.

Federal regulators oversee the trans-Alaska pipeline itself and other crude oil lines on the North Slope. The state oversees flow lines.

The state report was ordered by the Alaska Legislature after major spill in 2006. One was in a federally regulated oil line leading away from a processing plant.

Larry Dietrick, the state's spill response director, said Thursday the report reviewed hundreds of spill reports, from pinhole drips to leaks of more than 10,000 gallons, with an eye toward predicting future events.

The study looked at all components in the system - hundreds of miles of pipeline in the massive oil fields, processing centers and storage tanks. Valve seals, he said, are the No. 1 culprit for spills.

"But our big spill issues are all flow lines," he said, because of the potential for a major spill.

Some of the flow line pipes are big - as much as 24 inches in diameter, Dietrick said. They carry the most corrosive of the materials on the slope, he said, the three-way combination of oil, gas and water. And unlike a crude oil pipeline carrying a single fluid, they cannot be monitored for leaks 24 hours per day by a machine.

"These don't have an automated leak detection," he said. "Because of the three-phase flow, you can't get meters to run right."

Instead, they're inspected manually, but if an inspector eyeballs them only once every three days, you could have two days of spillage before a leak is spotted, he said.

Corrosion is a common cause of leaks and external corrosion was the most common cause of failure for flow lines.

The report did not detect changes in the number of spills per year but suggested the frequency of spills greater than 1,000 gallons has increased.

The report did not assess other risks associated with the industry, such as fires or gas leaks.

The DEC will sponsor a conference to investigate advances in leak technology detection. The results will be considered for potential new leak detection regulations for flow lines.

DEC is working with the Department of Law to examine penalties for spills to determine if statutes need updating.

It's a challenge for both the industry and the regulators to keep up as conditions change in the oil fields, Dietrick said. If sediment builds in lines, so can corrosion caused by microbes, which live in the sediment.

The industry uses more that 2 million gallons of corrosion inhibitor per year.

"The problem up there isn't that there's no program," he said. "It is a challenge to keep the programs calibrated to the changing conditions."

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