BILOXI, Miss. — Efforts to cap a leaking oil well in the Gulf of Mexico suffered a major setback Saturday after icy crystals clogged the inside of a 98-ton steel-and-concrete dome meant to contain the 18-day-long spill.
The crystals, which resemble slush, forced officials to move the dome, which is still on the sea bed, about 650 feet away from the well — and to scramble to find ways to stop the water-and-gas crystals from forming.
"I wouldn't say it failed yet," said Doug Suttles, chief operating officer of BP, the London-based company that owns the leaking well. "What I would say is what we attempted to do last night didn't work."
He kept expectations low, however. "It's very difficult to predict whether we will find solutions," he said.
A relief well intended to intercept the leaking one and seal it won't be completed for three more months.
Meanwhile, a Coast Guard official said tar balls that are believed to be from the Gulf of Mexico oil spill are washing up on an Alabama island.
Coast Guard Chief Warrant Officer Adam Wine said about a half dozen tar balls had been collected by Saturday afternoon at Dauphin Island. He said the substance needs to be tested, but officials think it came from the oil spill.
The barrier island is at the mouth of Mobile Bay and about three miles from the coast.
The oil slick, which has already come ashore on the Chandeleur Islands off the southeast coast of Louisiana, is projected to curl west in the next three days, threatening not only the Mississippi River Delta but also miles of Louisiana coastline to the west of the river.
The dome was considered the best short-term solution to stop much of the spill. Engineers had hoped to contain 85 percent of the estimated 210,000 gallons gushing daily from the well by funneling oil to the surface from the dome. The 40-foot box took about two weeks to build.
The crystals, which are called hydrates, obstructed the flow of the oil, Suttles said. They also made the dome too buoyant, which prevented it from settling deeply into the seabed to form a water-tight seal.
Hydrates form when gas and water mix at low temperature and high pressure, as occurs at the bottom of the sea. The water temperature at the wellhead is about 42 degrees, with pressures in excess of 2,300 pounds per square inch. In contrast, atmospheric pressure at sea level is about 14 pounds per square inch.
The Deepwater Horizon oil rig, owned by the Transocean offshore drilling company, exploded April 20 about 50 miles off the Louisiana coast.
The explosion was triggered by a bubble of methane gas that escaped from the well and shot up the drill column, expanding quickly as it burst through several seals and barriers before exploding, according to interviews with rig workers conducted during BP's internal investigation.
The interviews provide the most detailed account of the blast that killed 11 workers and touched off the underwater gusher that has poured more than 3 million gallons of crude into the Gulf.
Portions of the interviews, two written and one taped, were described in detail to an Associated Press reporter by Robert Bea, a University of California Berkeley engineering professor who serves on a National Academy of Engineering panel on oil pipeline safety and worked for BP PLC as a risk assessment consultant during the 1990s. He received them from industry friends seeking his expert opinion.
Six BP executives were on board the Deepwater Horizon rig at the time, celebrating the project's safety record, according to the transcripts.
Suttles had warned all week that problems could arise with the dome plan, which had never before been carried out at the depth of the leaking oil well — 5,000 feet below the surface of the Gulf of Mexico.
BP officials had cautioned that crystals would be a challenge and had hoped that pumping water down a hose into the dome would keep its temperature high enough to prevent crystals from forming.
Suttles said it is easy enough to unclog the dome — the crystals melt when the box is lifted higher in the water. The trick is to keep the gas and water from crystallizing while the box is on the sea bed, where it must be to capture the leaking oil.
Nearly 1 million feet of oil-absorbing boom has been placed along Gulf shores in hopes of blocking the oil from reaching land, Suttles said.
About 2.1 million gallons of an oil-water mix — about 90 percent water — have been collected since the spill began, the Coast Guard said Saturday, and almost 290,000 gallons of dispersants have been used to break up the oil on the water's surface.
"I don't think any of us know at this time what the impacts will be on the environment or the economic issues associated with this spill," said Coast Guard Rear Adm. Mary Landry, who is helping coordinate the federal response to the spill.
This report contains information from the Associated Press, McClatchy Newspapers and the New York Times.