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Response continues at Lisburne spill Quarter acre of frozen discharge remains while team waits for engineers to ensure that pressure has dropped in leaking pipeline Alan Bailey Petroleum News
The spill response crew has removed about 80 cubic yards of oil-misted snow from a half-acre area around the site of a pipeline leak in the Lisburne field on Alaska’s North Slope, and is waiting for the go-ahead to work closer to the site of the leak, to remove snow contaminated with a mixture of oil, produced water and gas in a quarter-acre area at the leak site, Alaska Department of Environmental Conservation spokeswoman Weld Royal told Petroleum News Dec. 2.
Routine check A BP operator making a routine check discovered the leak just after 3 a.m. on Nov. 29 — oil was dripping from an above-ground, 18-inch pipeline about one-and-a-half miles east of the Lisburne Production Center in the BP-operated Prudhoe Bay unit. The 1980s-era pipeline and an accompanying 24-inch line carry three-phase fluids from Lisburne drill pad L-3 to the production center.
Following discovery of the leak, an incident management team was formed, under a unified command with an incident commander from BP and on-scene commanders from the Alaska Department of Environmental Conservation, the federal Environmental Protection Agency and the North Slope Borough.
Because of concerns about a possible accident resulting from the release of further oil from the pipeline, responders are waiting until engineers determine with certainty that pressure within the line is at a safe level, BP spokesman Steve Rinehart told Petroleum News Dec. 2. Although the line had been out of use for two or three weeks prior to the incident, possible ice blockages in the line could cause a pressure buildup, Rinehart explained.
And as an additional precaution, the response crew has strapped the pipeline to its support members, to ensure that the line would not move in the event of a sudden internal pressure kick, he said.
Exclusion zone With an exclusion zone 20 feet across imposed around the leak while the safety issues are resolved, it has not yet proved possible to assess the exact nature of the leak. And, with the heavily contaminated snow close to the leak yet to be removed, there is as yet no estimate of the volume of oil and water spilled.
In a media briefing on Dec. 3, Randy Selman, BP incident commander, said that the response team is starting the second phase of the response operation: the construction of a support pad and an ice pad.
“The responders on the North Slope are a little over 100 personnel plus state, federal and local agencies, and we have a support staff in Anchorage that is supporting the operation,” Selman said.
The support pad is being constructed close to the spill site, using rig mats, to act as a holding location for heavily contaminated snow, when people dig out the oil- and produced-water-laden material. The contaminated material will then be moved to the ice pad, about one and a half miles from the spill site, for the melting, measurement and recycling of the contaminants, Selman explained.
Meantime, x-ray equipment will be used to locate any ice plugs in the pipeline, to enable resolution of the risk of a pressure buildup, he said.
But although safety concerns have prevented a close examination of the leak, it appeared that by Nov. 30 the leak had either stopped or had dwindled to a very low rate. The mixture of oil and water dripping from the pipeline had frozen in the snow.
“It is doing something that I think … many of us seasoned responders have never seen before,” said Federal On-scene Commander Matt Carr from EPA during the Dec. 3 briefing. “… You have this large dome of semi-solid material … like a very stiff snow cone. It’s piled up in a roughly circular kind of a deposition and about five feet in thickness at its apex.”
Cause unknown Although BP has started an investigation into the cause of the leak, that cause will not be established until people can examine and investigate the leak site, once the site safety concerns have been resolved.
But although the damaged pipeline was not designed for inspection using a pig, an instrumented device that can travel through the pipeline interior, the pipeline has been inspected regularly, using techniques for the detection of corrosion and other defects both on the interior and exterior of the line, Rinehart said.
The pipeline has been subject to a five-year inspection schedule, having been inspected by ARCO in 1998 and by BP in 2003 and 2008, he said.
“We determined this line was fit for service,” Rinehart said.
But, what of impacts on production from the Lisburne field, while the damaged line is out of action?
With the 24-inch line that runs alongside the leaking 18-inch line having adequate capacity to handle production from the L-3 pad, there has been little impact on production to date, and there should be no long-term production impact from the spill, Rinehart said.
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