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‘Top kill’ awaits BP greenlight, success remains uncertain

BP is still awaiting test results before initiating a difficult “top kill” procedure to plug the Gulf oil spill, its most ambitious effort to date. But executives caution that the procedure has never been attempted at depths of 5,000 feet and may not be successful.

A top kill involves injecting heavy liquids, or “kill mud,” through a series of pipes into the damaged blow-out preventer at a rate of 50 barrels per minute. The leaking oil will push back against the mud, but the hope is that the weight of the mud will eventually overwhelm the oil and push it down. If successful, the leak will be capped permanently with cement.

But if the pressure from the rising oil and gas is too great for the mud, BP may attempt a “junk shot” — pumping solid materials such as shredded tires, golf balls and pieces of rope into the well — to slow the oil flow and allow more kill mud to flow in.

“We’ve been testing the junk shot on-shore, looking at different configurations of what might restrict the flow out of the Deepwater Horizon riser and what types of materials would help shut it off,” BP wrote on their website Sunday.

The challenge at every step of the process is to successfully monitor and manipulate pressure levels.

If greenlit, the top kill will take two days to complete and an additional few days to determine if it’s been successful.

The stakes are high, the New York Times reports:

Successful capping of the leaking well could finally begin to mend the company’s brittle image after weeks of failed efforts, and perhaps limit the damage to wildlife and marine life from reaching catastrophic levels.

A failure could mean several months more of leaking oil, devastating economic and environmental impacts across the gulf region, and mounting financial liabilities for the company. BP has already spent an estimated $760 million in fighting the spill, and two relief wells it is drilling as a last resort to seal the well may not be completed until August.

For help visualizing a top kill, see a simplified diagram here and an animated graphic at 0:34 in this video.

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