NEW ORLEANS — BP finished pumping fresh cement into its blown-out oil well Thursday as it aimed to seal for good the ruptured pipe that for months spewed crude into the Gulf of Mexico in one of the world's worst spills.
A day before, crews forced heavy mud down the broken wellhead from ships a mile above to push the crude back to its underground source. The cement was the next step in the so-called "static kill" and is intended to keep the oil from finding its way back out.
"This is not the end, but it will virtually assure us that there will be no chance of oil leaking into the environment," retired Adm. Thad Allen, who is overseeing the spill response for the government, said in Washington.
The progress was another bright spot as the tide appeared to be turning in the months-long battle to contain the oil. A federal report this week indicating that only about a quarter of the spilled crude remains in the gulf and is degrading quickly.
Even so, Joey Yerkes, a 43-year-old fisherman in Destin, said he and other boaters, swimmers and scuba divers continue to find oil and tar balls in areas that have been declared clear.
"The end to the leak is good news, but the damage has been done," Yerkes said.
If the mud plug in the blown-out well is successfully augmented with the cement, the final step involves an 18,000-foot relief well that intersects with the old well just above the vast undersea reservoir that had been losing oil freely since the Deepwater Horizon rig exploded off Louisiana on April 20, killing 11 workers.
It could take at least a day for the cement pumped into the blown well to cure, and another five to seven days for crews to finish drilling the final 100 feet of the relief well. Then the pumping process in the relief well could last days or even weeks, depending on whether engineers find any oil leaks, Allen said.
BP executives and federal officials won't declare the threat over until they use the relief well — though lately they haven't been able to publicly agree on its role.
Federal officials, including Allen, have insisted that crews will shove mud and cement through the 18,000-foot relief well, which should be completed within weeks. Crews can't be sure the area between the inner piping and outer casing has been plugged until the relief well is complete, Allen said.
However, BP officials have in recent days refused to commit to pumping cement down the relief well, saying only that it will be used in some fashion.
"The ultimate objective is getting this well permanently sealed," BP senior vice president Kent Wells said Wednesday.
Allen clearly said again Thursday that to be safe, the gusher will have to be plugged from two directions, with the relief well used for the so-called "bottom kill."
"The well will not be killed until we do the bottom kill and do whatever needs to be done," he said, adding: "I am the national incident commander and I issue the orders. This will not be done until we do the bottom kill."