* Small “top hat” dome one of several options, BP says
* Will take 72 hours, won’t capture as much leaking oil
* “Junk shot” to plug blow-out preventer to take two weeks (Recast, adds details, quotes; byline)
HOUSTON, May 10 (Reuters) - BP Plc BP.L will try to place a much smaller containment dome over a blown-out oil well about a mile (1.6 km) underwater to trap the gusher of crude that endangers the U.S. Gulf Coast, the company's chief executive said on Monday.
The so-called “top hat” could be in place within 72 hours and is one of a number of attempts the British oil major is making to stem the flow of crude from a well in the U.S. Gulf of Mexico that threatens the coastlines of four states.
“We continue to fight this very aggressively on three fronts; in the subsea to eliminate the leak, on the surface to to contain the spill offshore, and along the shore to defend the shoreline,” BP CEO Tony Hayward said during a surprise appearance at a media briefing in Houston.
BP attempted to install a massive containment device over the larger of two leaks on the sea floor to funnel oil to the surface for collection.
But after lowering the huge dome into the sea on Thursday night the company said on Saturday that chamber was blocked by hydrates, or crystallized gas, and had to be removed.
“There’s a lot more gas involved in this leak than we had believed,” Hayward said.
Hydrates are crystals formed at high pressure and low temperature where water and natural gas are found. There will be less seawater in the smaller dome, which will reduce the chance of hydrate formation, the CEO said.
“It’s unlikely to be as effective (as the larger dome) in capturing all of the oil,” Hayward said, but it will be more effective in reducing hydrate formation.
The original dome, which took about two weeks to build, was four stories high and weighed 98 tons. The smaller dome, which will be anchored to the sea floor with pipe, is four feet (1.2 metres) in diameter and five feet (1.5 metres) high, BP said.
The company is also planning to try and block the crude flow with a “junk shot,” in which materials including golf balls, knotted rope and shredded tires will be shot at high pressure into the well’s failed subsea blow-out preventer.
That process will take about two weeks, BP said.
All of the techniques BP is trying have never been attempted at the water depths of this well, which is 5,000 feet (1,500 metres) below the surface and where equipment is being maneuvered with remotely controlled vehicles. (Reporting by Anna Driver in Houston; Editing by Ros Krasny and Eric Walsh)
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