HOUMA, La. — Engineers have stopped the flow of oil and gas into the Gulf of Mexico from a gushing BP well, the federal government’s top oil-spill commander, U.S. Coast Guard Adm. Thad Allen, said Thursday morning.
The “top kill” effort, launched Wednesday afternoon by industry and government engineers, had pumped enough drilling fluid to block oil and gas spewing from the well, Allen said. The pressure from the well was very low, he said, but persisting.
Once engineers had reduced the well pressure to zero, they were to begin pumping cement into the hole to entomb the well. To help in that effort, he said, engineers also were pumping some debris into the blowout preventer at the top of the well.
As of early Thursday morning, neither government nor BP officials had declared the effort a success yet, pending the completion of the cementing and sealing of the well.
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Allen said one ship that was pumping fluid into the well had run out of the fluid, or “mud,” and that a second ship was on the way. He said he was encouraged by the progress.
“We’ll get this under control,” he said.
Last week, BP inserted a mile-long tube to siphon some of the oil into a tanker. The tube sucked up 924,000 gallons of oil, but engineers had to dismantle so they could start the top kill.
If that works, BP will then inject cement into the well to seal it. The top kill has been used above ground but has never before been tried 5,000 feet beneath the sea. BP pegged its chance of success at 60 to 70 percent.
Lt. Commander Tony Russell, an aide to Allen, said Thursday that the flow of mud was stopping some oil and gas but had a ways to go before it proved successful.
"As you inject your mud into it, it is going to stop some hydrocarbons," he said. "That doesn't mean it's successful."
BP spokesman Tom Mueller also discounted news reports that the top kill had worked.
"We appreciate the optimism, but the top kill operation is continuing through the day today — that hasn't changed," he said Thursday morning. "We don't anticipate being able to say anything definitive on that until later today."
Meanwhile, the Gulf oil spill has surpassed the Exxon Valdez as the worst in U.S. history, according to new estimates released Thursday, but the Coast Guard and BP said an untested procedure to stop it seemed to be working.
A team of scientists trying to figure out how much oil has been flowing since the offshore rig Deepwater Horizon exploded April 20 and sank two days later found the rate was at least twice and possibly up to five times as high as previously thought.
Even using the most conservative estimate, that means the leak has grown to nearly 19 million gallons, surpassing the size of the 1989 Exxon Valdez disaster, which at about 11 million gallons had been the nation's worst spill. Under the highest estimate, nearly 39 million gallons may have spilled.
U.S. Geological Survey Director Marcia McNutt said two different teams of scientists calculated that the well has been spewing between 504,000 and more than 1 million gallons a day.
BP and the Coast Guard estimated soon after the explosion that about 210,000 gallons a day was leaking, but scientists who watched underwater video of well had been saying for weeks it was probably more.