ANCHORAGE (AP) -- BP Exploration (Alaska) Inc. plans to shut down and test about 150 North Slope oil wells in response to an explosion that seriously injured a worker earlier this month.
The company said it wants to prevent a repeat situation in another well with pressure build-up similar to the well that ruptured and caught fire Aug. 16.
Company officials said the shutdown is an unprecedented safety move. Together the wells produce about 60,000 barrels of oil a day -- 6 percent of total North Slope production.
Under on current prices, oil flow worth about $1.7 million a day could be interrupted.
Steve Marshall, president of BP Exploration (Alaska) Inc., said an investigative team including some of BP's top global experts recommended the wells be shut down and tested, and he agreed. Marshall said he notified Gov. Tony Knowles Saturday.
''We're all deeply affected by the fact that one of our people was severely hurt. And we won't stop until we get to the bottom of what happened,'' Marshall told the Anchorage Daily News.
The wells won't be shut down all at once, but in phases over the next week to 10 days. Marshall said the goal is to bring the wells back on stream as quickly as possible.
Don Shugak, a veteran BP oil field operator, suffered burns and broken bones as he prepared to bleed off pressure from a well on A Pad at Prudhoe Bay, North America's largest oil field.
Meanwhile, the Alaska Department of Environmental Conservation is investigating, along with BP.
BP investigators believe one of the well's steel pipes or casings ruptured under pressure about 17 feet below ground, releasing a torrent of natural gas into the small metal building covering the wellhead. The gas uprooted flooring timbers and gravel in the wellhouse, sparking an explosion and fire that burned like a giant torch off a broken valve.
The well, known as A-22, was drilled in 1982 to a depth of 12,316 feet and is among about three dozen oil or injection wells on the 60-acre gravel pad. About 1,600 wells are spread across Prudhoe Bay.
A-22 had been down for six days before the explosion, in part because of maintenance elsewhere in the oil field but also because of an abnormal pressure in the outer annulus.
The limit is 1,000 pounds per square inch, but a field operator found a reading twice that high three days before the explosion and bled off some of the pressure, investigators said. A subsequent test found the well met criteria to resume operation, and Joe Anders, BP well integrity engineer for Prudhoe Bay, said he gave the OK late in the afternoon before the explosion to bring A-22 back on stream.
Shugak evidently found overpressuring and could have been heading out to his truck for a hose to bleed it off when the underground casing failed and the wellhouse exploded, said Fritz Gunkel, leader of BP's investigative team.
Investigators haven't been able to talk to Shugak, who is in the burn unit of a Seattle hospital, but he told emergency medical workers that a well pressure gauge indicated 2,700 psi.
The pipe is actually rated to withstand pressure nearly twice that high, Anders said.
The 150 wells slated for shutdown are all ''yellow tag'' wells exhibiting the same overpressuring as A-22, Gunkel said.
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