ON THE GULF OF MEXICO – BP claimed a key victory Wednesday in the effort to plug its blown-out well as the government said much of the spilled oil is gone — though what's left is still at least quadruple the amount that poured from the Exxon Valdez.
BP PLC reached what it called a significant milestone overnight when mud that was forced down the well held back the flow of crude. That means the procedure known as a "static kill" appears to be working, though crews now must decide whether to follow it up with cement.
Federal officials won't declare complete victory until they pump in mud and then cement from the bottom of the well, and that won't happen for several weeks.
"We've pretty much made this well not a threat, but we need to finish this from the bottom," retired Coast Guard Adm. Thad Allen, the government's point man on the spill response, told WWL-TV in New Orleans.
White House energy adviser Carol Browner said on morning TV talk shows that a new assessment found that about 75 percent of the oil has either been captured, been burned off, evaporated or broken down in the Gulf.
"It was captured. It was skimmed. It was burned. It was contained. Mother Nature did her part," Browner told NBC's "Today" show. On ABC's "Good Morning America," she said about 25 percent remained.
About 205 million gallons gushed in total from the well, based on government estimates released this week, meaning that if Browner's comments hold true about 51 million gallons remain in the Gulf. Crews managed to burn, skim or siphon off 33 million gallons in the days after the April 20 explosion aboard the offshore drilling rig Deepwater Horizon.
Even if the Gulf well had leaked only 51 million gallons to begin with, it would still rate among the worst oil spills in history. By comparison, the Exxon Valdez spill that wreaked environmental havoc in Alaska in 1989 spilled 11 million gallons.
A 75-ton cap placed on the well in July has been keeping the oil bottled up inside over the past three weeks but was considered only a temporary measure. BP and the Coast Guard wanted to plug up the hole with a column of heavy drilling mud and cement to seal it off more securely.
The static kill — also known as bullheading — involved slowly pumping the mud from a ship down lines running to the top of the ruptured well a mile below. A previous, similar effort failed in May when the mud couldn't overcome the unstemmed flow of oil.
BP won't know for certain whether the static kill has succeeded until engineers can use the soon-to-be-completed relief well to check their work.
In the Gulf, workers stopped pumping mud in after about eight hours of static kill work and were monitoring the well to ensure it remained stable, BP said.
"It's a milestone," BP PLC spokeswoman Sheila Williams said. "It's a step toward the killing of the well."
The next step would be deciding whether to cement the well.
The pressure in the well dropped quickly in the first 90 minutes of the static kill procedure, a sign that everything was going as planned, wellsite leader Bobby Bolton told The Associated Press on Tuesday.
Browner told NBC it was good news that the static kill was working but that "we remain focused on the relief well."
BP has said the static kill might be enough by itself to seal the well. But the 18,000-foot relief well that BP has been drilling for the past three months will be used later this month to execute the "bottom kill," in which mud and cement will be injected into the bedrock 2 1/2 miles below the sea floor to finish the job, Allen said Tuesday.
"There should be no ambiguity about that," Allen said. "I'm the national incident commander, and this is how this will be handled."
The task is becoming more urgent because peak hurricane season is just around the corner, Allen said. Tropical Storm Colin formed then dissipated far out in the Atlantic on Tuesday, but early forecasts say it will travel toward the East Coast rather than the Gulf.
Read this story on Yahoo News: "BP plugs well with mud; feds say much of oil gone"