The Top Kill, Working in Slow Motion

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Patrick Kelley / U.S. Coast Guard / Getty Images

The mobile offshore-drilling unit Q4000 sits directly above the damaged Deepwater Horizon blowout preventer while crews attempt a technique known as "top kill" to plug the wellhead on May 26, 2010, in the Gulf of Mexico

The spiraling disaster that is the BP oil spill has at least one more day to run. That was the word from BP chief operating officer Doug Suttles at a press conference on Thursday, May 27, more than 25 hours after the company's much awaited top-kill procedure got under way. Following a day of encouraging news — and a false report from the Los Angeles Times that the leak had actually been stopped — a weary-looking Suttles had one message: Not so fast.

Part of the reason for the caution is that the top-kill exercise is actually more complicated than it looks in the live feeds from the ocean floor. Despite what most people think, the drilling mud that is intended to plug the leak cannot be pumped into the broken well nonstop. Indeed, the procedure, which began at 2 p.m. on Wednesday, was halted at midnight Wednesday night and not resumed again until late Thursday afternoon. The matter seen in live videos billowing from the pipes is mud, not oil — which is good as far as it goes. But the fact that the flow continues means the upward pressure of the rising oil is still greater than the downward pressure of incoming mud. Only when those pressures cancel each another out will the top kill be considered a success and the company able to begin pumping in cement to seal the well permanently.

"This is called a 'dynamic kill,' " Suttles explained — which means engineers pump for a while, then stop to measure oil pressure and flow rates and make any necessary adjustments. Those adjustments may include increasing the density and weight of the drilling mud and raising the pressure applied by the 30,000-horsepower pump on the surface. Late Thursday, the assessments were essentially done, and the pumping resumed with an additional 15,000 barrels of mud — which would follow the 50,000 that have been poured down the throat of the well already.

More troubling than the fact that an operation that was advertised as perhaps a 24-hour job will now go on at least 48 was Suttles' admission that the operation won't be sufficient to get the job done. Sometime tonight, BP also plans to inject so-called bridging material — a coarser, flakier occluding agent than mud — into the riser pipe. The bridging agent, in turn, might be followed by the much discussed "junk shot," in which shredded tires, golf balls, knotted rope and other chokables are used to block the oil.

Suttles mentioned the junk shot twice during Thursday's press conference, which probably took some courage, since over the past few weeks it's been derided — rightly or wrongly — as a move of total desperation. Certainly, BP officials hadn't spoken of it much in the past day, which means either that they simply forgot to mention that it was so immediate a possibility or that they hoped it wouldn't be but the slower than expected progress of the top-kill strategy made it necessary. Suttles did not say which it was. Nor was he very specific when asked if he was still optimistic that the top kill would succeed.

"It's quite a roller coaster," he answered. "We want it to be successful, but the well continues to flow. I'm not optimistic or pessimistic."

One reading of the press-conference tea leaves might tip things slightly toward the pessimistic side. On two unbidden occasions, Suttles made a point of stressing that if the top kill fails, BP is ready to pivot straight to the "top hat," a dome that would be lowered over the leak to contain it, or to the more complex job of installing a new blowout preventer (a valve that would seal the well shut) over the one that failed. Not that such measures will be necessary, of course — unless they are.