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"Top kill" fails to stop flow of oil in Gulf of Mexico

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NOAA-spill-map-May-28-2010Despite golf balls, tires, 30,000 horsepower of pumps and 30,000 barrels of dense drilling mud chock full of barite, BP's so-called "top kill" operation failed to stop the disastrous oil leak in the Gulf of Mexico and was abandoned on the afternoon of May 29. The idea was to muscle the oil back into the well with a steady stream of mud—a technique that has worked on land.


But with 5,000 feet of pipe just to get to the blowout preventer and wellhead, the mud was never able to overcome the flow of oil and silt up the well, said BP Chief Operating Officer Doug Suttles at a press briefing. BP now will move to attempt the so-called lower marine riser package technique, which involves cutting the riser pipe free from the blowout preventer and putting a cap—not a top hat—over the pipe, hopefully eliminating all the oil flowing into the sea. The package is already resting on the seafloor but it will be four to seven days before BP makes the attempt, said Coast Guard Rear Admiral Mary Landry. BP's Suttles says placing such a device on top of a blowout preventer has never been attempted before at a deep water well, such as Mississippi Canyon 252, which may have released as much as 40 million gallons of oil into the Gulf of Mexico to date.


In the meantime, 170,000 gallons of dispersants have been injected beneath the sea surface to break up the oil, which has been flowing now for 40 days, though Suttles noted that BP would not be able to remove any of the dispersed oil in sub-surface plumes. BP continues to use the dispersant Corexit, which can include toxic solvents such as 2-butoxyethanol. To date, 930,000 gallons of various versions of Corexit have been used, both at the surface and near the well.


The failure of top kill is a major setback as BP had offered a 60 to 70 percent chance of success. Suttles declined to give an estimate for the lower marine riser package effort, but expressed confidence the effort could work. "We do have a lot of confidence, but I'm not going to quote a number," Suttles said. "There clearly is a risk it won't work." He also noted that it would be easier to watch the effort unfold as the mud involved in top kill had obscured the view previously.


Regardless of the success or failure of the package, the flow at the well will not be fully stopped until August at the earliest, when at least one of two relief wells being drilled intersects the currently flowing well and cuts it off. Added Suttles: "This scares everybody, the fact that we can't make this well stop flowing, the fact that we haven't succeeded so far."

Image: NOAA

The views expressed are those of the author and are not necessarily those of Scientific American.

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