Best hope to stop spill? Relief wells, but they're tricky
06/04/2010 6:23 PM
08/02/2010 6:20 PM
WASHINGTON — The last, best hope of stopping the oil that's gushing into the Gulf of Mexico is two "relief wells" that are being drilled, but they won't be finished until August.
While some scientists are skeptical that BP will be able to connect the relief wells to the original well bore on the first attempt — David Rensink, the incoming president of the American Association of Petroleum Geologists, has said the probability is "virtually nil" — others say that drilling a relief well is easier than drilling the primary well.
"A relief well is a standard operation when (companies) have blowouts," said Peter Clark, an associate professor of mineral engineering at the University of Alabama. "If they can't control (the flow) any other way, they drill a relief well."
Clark said he was optimistic that the relief wells would work, even though they must link up with a small pipe about 18,000 feet below sea level.
"Nothing that is being done to date is new technology," Clark said. "It's technology that has been used in other places, just not at this depth. They are not inventing anything. If they miss, they can back up and try again. It's not an all-or-nothing shot."
BP has every incentive to get it done as fast as possible, he said: "They are not going to cut any corners putting that relief well in. This is already costing them a fortune."
To improve its chances for success, BP is drilling two emergency wells at once, one 12,090 feet deep, the other 8,576 feet, but neither will be completed until August, more than 90 and perhaps as much as 120 days after the Deepwater Horizon rig exploded on April 20.
The relief wells' chances for success are enhanced because BP engineers already know the geology from having bored the first well.
BP "has a big advantage here because they have already drilled the original well, so they have a blueprint," said Stephen Sears, the chair of the Department of Petroleum Engineering at Louisiana State University. "They know the geology and they know the pressures. The big uncertainly is weather."
Hurricanes could delay things. Hurricane season began Tuesday, and BP would have to halt drilling and evacuate the rig that's overseeing the relief wells if a storm threatened. The National Oceanic and Atmospheric Administration recently projected that the Atlantic is likely to see eight to 14 hurricanes this season, with three of those likely to be major storms.
"We're going into hurricane season. Therefore, you need to have a plan for how you would suspend operations, if you had to, because of the weather," Coast Guard Adm. Thad Allen, who's overseeing the Gulf spill operation, said at a news conference Tuesday.
While the plan is to bring in a rig capable of withstanding "violent weather," Allen said, "nothing is fail-safe with hurricane season coming."
Relief wells have been used in the Gulf of Mexico before, but the precedent is discouraging. In 1979 the Ixtoc oil spill gushed for more than ninth months after a blowout; some 3 million barrels of oil are estimated to have been released before the leak was halted. The owner of the Ixtoc rig was Petroleos Mexicanos.
Last year an oil-rig explosion off the Australian coast required five attempts and 10 weeks before a relief well could plug it.
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