Gulf of Mexico Oil Well Plugged

BP reached a "significant milestone" Wednesday in its bid to end the worst oil spill in history, using a procedure called a "static kill" to bring its runaway well in the Gulf of Mexico under control.

After pumping heavy drilling fluid into the busted well for eight hours, the company said "the MC252 well appears to have reached a static condition -- a significant milestone."

"The well pressure is now being controlled by the hydrostatic pressure of the drilling mud, the desired outcome of the static kill procedure," it said in a statement.

The apparent breakthrough came 106 days after a devastating explosion aboard the BP-leased Deepwater Horizon rig on April 20 killed 11 workers and unleashed a torrent of oil into the Gulf.

The 4.9-million-barrel spill -- by far the biggest on record -- threatened the fish and wildlife-rich Gulf Coast with environmental ruin and plunged residents of coastal communities into months of anguish over their livelihoods and the region's future.

BP also emerged from the ordeal many billions of dollars poorer and with its reputation tarnished by a succession of failures to stop the leak and public relations gaffes by ousted CEO Tony Hayward.

In its statement, BP said it still might pump more mud into the well in order to push leaking crude oil back into its source rock.

"The well is now being monitored, per the procedure, to ensure the well remains static," it said. "Further pumping of mud may or may not be required depending on the results observed during monitoring."

It said it would continue to work with the Obama administration's point man Thad Allen "to determine the next course of action, which includes assessing whether to inject cement into the well via the same route."

Officials had said that complications could arise if the well's casing was found to have leaks, in which case they might have to hold off sealing it with cement until a relief well is complete.

BP said that in any event it will continue to drill a relief well to cut off and seal the well from the bottom, ensuring that the plug is final.

Allen, the Coast Guard admiral who has overseen the government's response to the spill, was emphatic on Tuesday that the static kill "will increase the probability that the relief well will work."

In the long run, "drilling into the annulus and into the casing pipe from below, filling that with mud and then filling that with cement is the only solution to the end of this," he told reporters.

The extent of the leak was confirmed when U.S. government experts on Monday announced that the oil had been pouring out at a rate of 62,000 barrels a day -- more than 12 times faster than BP originally admitted.

This was also higher than any previous official estimate, and meant 4.9 million barrels of crude -- more than 205 million gallons -- spewed into the Gulf in the 87 days it took to cap it.

If BP is found guilty of negligence, the flow rate means it could face up to $17.6 billion in fines. The firm has also set up a $20 billion fund to pay claims from individuals and businesses hit by the disaster.

The New York Times, however, said the U.S. government was expected to announced Wednesday that three quarters of the oil has already evaporated, dispersed, captured or otherwise eliminated.

About 26 percent of the oil was still in the water and could cause new problems, the report said, but government scientists believe it is breaking down rapidly.