ROBERT, Louisiana (Reuters) - BP Plc suffered a setback on Saturday in an attempt to contain oil gushing into the Gulf of Mexico with a metal box when crystallized gas filled the structure, a blow to hopes of a quick, temporary solution to a growing disaster.
BP engineers have moved the four-story containment dome -- which was seen as the best short-term way to stem the flow from a ruptured oil well -- off to the side on the sea floor and will take two days trying to come up with a solution, Doug Suttles, chief operating officer, told reporters.
The problem is with gas hydrates, essentially slushy methane gas that would block the oil from being siphoned out the top of the box. As BP tries to solve it, oil keeps flowing unchecked into the Gulf in what could be the worst U.S. oil spill.
"I wouldn't say it's failed yet. What I would say is what we attempted to do last night didn't work because these hydrates plugged up the top of the dome," Suttles said.
"What we're currently doing, and I suspect it will probably take the next 48 hours or so, is saying, 'Is there a way to overcome this problem?'"
The company, under pressure from the Obama administration to limit the damage to the Gulf and coastlines of four states, expected hydrates, but not the volumes encountered after a crew lowered the dome nearly a mile to the sea floor.
Possible solutions may involve heating the area or adding methanol to break up the hydrates, Suttles said.
Officials had already warned there was no guarantee that the technology would work at such water depth.
BP had spent the previous day or so lowering the 98-ton contraption to the well site with the aid of sensors, video cameras and undersea robots.
It hopes to attach a pipe to the chamber to start pumping oil up to a tanker, with the aim of capturing about 85 percent of the leaking oil.
The spill threatens an economic and ecological disaster targeting beaches, wildlife refuges and fishing grounds in Louisiana, Mississippi, Alabama and Florida. It has forced President Barack Obama to rethink plans to open more waters to drilling.
BP suffered another blow on Friday when ratings agency Standard & Poor's lowered its outlook on the British oil giant to negative from stable. It has said it will pay all legitimate costs, a bill that is likely to run into the billions of dollars.
The company gave up on efforts to close valves on a failed blowout preventer with underwater robots, after trying in vain for two weeks. Suttles said BP may now try to plug up the existing preventer or attach a new one on top of it.
It also is drilling a relief well to halt the leak -- which began after the Deepwater Horizon rig exploded on April 20, killing 11 crew members -- but it could take up to three months to complete.
In the initial blast, a natural gas cloud enveloped the rig and exploded just as visiting BP officials were celebrating seven accident-free years in the rig's crew quarters, according to accounts by survivors of the blast.
According to transcripts of interviews obtained by Robert Bea, a University of California Berkeley engineering professor, a giant methane bubble rushed up the drill pipe and filled the air above the deck of the drilling platform with flammable gas, followed by a scalding flood of crude that spilled onto the drill deck and ignited.
Nine workers on the drill deck were killed, along with two others working in the nearby mud storage room, Bea said.
After several days of calm weather, winds began to pick up on Saturday, preventing controlled burns of the thickest concentrations of oil. Crews conducted five burns on Friday.
Nearly 200 boats deployed protective booms and used dispersants to break up the thick oil on Saturday. Crews have laid almost 900,000 feet of boom, and spread 267,000 gallons (1 million liters) of chemical dispersant.
In Bayou La Batre, the heart of Alabama's seafood industry, the docks were largely quiet as thousands of shrimpers and seafood processors remained idled by fishing restrictions prompted by the oil spill.
About 30 oyster-processing plants have run out of product and shut down, putting as many as 900 people out of work, said Wayne Eldridge, owner of J&W Marine Enterprises and an oyster plant operator himself.
"I'm screwed," Eldridge said. "The biggest thing is I've got 35 people unemployed there."
BP Chief Executive Tony Hayward said a $75 million legal cap on the companies' liabilities for economic damages under federal law, which some U.S. lawmakers now want to raise, would not be a limit and renewed promises to meet all "legitimate" claims.
Standard & Poor's, in announcing BP's negative outlook, indicated a ratings downgrade was likely. Moody's said the spill raised the specter of credit pressure for the five primary companies involved in the project.
S&P cut its outlook for Anadarko Petroleum Corp, which has a 25 percent stake in the ill-fated well, to stable from positive, saying it is "potentially liable for significant costs and liabilities relating to the clean-up."
Other companies involved are Transocean, owner of the rig; Cameron International, which supplied the failed blow-out preventer for the well; and Halliburton, which helped cement in place the blown-out well.
An estimated 5,000 barrels (210,000 gallons/795,000 liters) have poured into the Gulf each day since the well ruptured. But Ian MacDonald, a biological oceanographer at Florida State University, said the estimate was much too conservative.
The real flow rate from the undersea well, based on aerial images of the oil slick and estimates of the thickness of the oil itself, is probably closer to 25,000 barrels (1.05 million gallons/4 million liters) per day, MacDonald told Reuters.
A sheen of oil has engulfed much of the Chandeleur Islands, barrier islands that are part of Louisiana's Breton National Wildlife Refuge, the first confirmation of the oil slick hitting land. Some oiled birds have been found in recent days.
BP contractors and commercial fishermen worked feverishly in waist-deep water to anchor booms around tiny uninhabited barrier islands as thousands of birds watched, according to a Reuters photographer.
The Breton refuge was closed to the public after a silver sheen and emulsified oil reached the shoreline, the U.S. Fish & Wildlife Service said. Altogether, crude from the spill could hit 24 national wildlife refuges.
(Additional reporting by Matt Bigg in Venice, Louisiana; Matt Daily in New York; Tom Bergin in London; Anna Driver, Bruce Nichols and Chris Baltimore in Houston; Tom Brown and Pascal Fletcher in Miami; Karen Brettell in New York; Steve Gorman and Brian Snyder in Mobile, Alabama; and Richard Cowan in Washington; writing by Jeffrey Jones and John Whitesides; editing by Mohammad Zargham)