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Waste and Emissions»100-tonne box to prevent oil spill

»Friday, May 7,2010

Deepwater team attempts to put 100-tonne box over blown-out oil well - 'Cofferdam' has never been used in such deep waters but may be quickest way stop loss of 200,000 gallons of oil a day.

A mission to the sea floor to try to avert a wider environmental disaster following the Deepwater Horizon oil spill made progress today as crews said a 100-tonne concrete-and-steel box was close to being placed over a blown-out well on the Gulf floor in an unprecedented attempt to contain the gushing oil.

Douglas Peake, the first mate of the supply boat that brought the box to the site, confirmed that a radio transmission from the nearby vessel lowering the device said it would soon be in position over the well.

The transmission said undersea robots were placing buoys around the main oil leak to act as markers to help line up the 40 foot (12 metre) box.

The box was about 4,000ft (1,200m) underwater before dawn on Friday with another 1,000ft to go, said Shawn Eggert, a coast guard petty officer.

Late last night, a crane lowered the containment vessel designed to collect as much as 85% of the oil spewing into the Gulf and funnel it up to a tanker. Eventually, the crane will give way to underwater robots that will secure the contraption over the main leak at the bottom, a journey that will take hours.

A steel pipe will be installed between the top of the box and tanker. If all goes well, the whole structure could be operating by Sunday.

"We haven't done this before," said BP spokesman David Nicholas. "It's very complex and we can't guarantee it [will work]."

BP plc is in charge of cleaning up the mess. The company was leasing the drilling rig Deepwater Horizon that exploded 80km (50 miles) out in the Gulf of Mexico on 20 April, killing 11 workers and blowing open the well. The site has since then been spewing an estimated 200,000 gallons (757,000 litres) a day in the nation's biggest oil spill since the 1989 Exxon Valdez disaster in Alaska.

The quest took on added urgency as oil reached several barrier islands off the Louisiana coast, many of which are fragile habitats for local wildlife. Birds were spotted diving into the oily, pinkish-brown water, and dead jellyfish washed up on the uninhabited islands.

Fishermen were also deeply concerned about the situation. "It's all over the place. We hope to get it cleaned up before it moves up the west side of the river," said Dustin Chauvin, a 20-year-old shrimp boat captain from Terrebonne Parish, Louisiana. "That's our whole fishing ground. That's our livelihood."

The crew of a semi-submersible drilling vessel, Helix Q4000, were forced to wait hours longer than expected to hoist the containment contraption from the deck of the Joe Griffin supply boat, because dangerous fumes rising from the oily water on a windless night had delayed the work. Joe Griffin's captain, Demi Shaffer, said the fear was that a spark caused by the scrape of metal on metal could cause a fire.

The technology has been used a few times in shallow waters, but never at such extreme depths. At a depth of 5,000ft, the water pressure is enough to crush a submarine.

Risks include ice clogs in the pipes – which crews will try to prevent by continuously pumping in warm water and methanol – and the danger of explosion when separating the mix of oil, gas and water brought to the surface.

"I'm worried about every part, as you can imagine," said David Clarkson, the BP vice-president of engineering projects.

If the box works, a second one now being built may be used to deal with a second, smaller leak from the sea floor.

This is just one of many strategies being pursued to stave off a widespread environmental disaster. BP is drilling sideways into the blown-out well in the hope of plugging it from the bottom. In addition, oil company engineers are examining whether the leak could be shut off by sealing it from the top instead.

The technique, called a "top kill," would use a tube to shoot mud and concrete directly into the well's blowout preventer. The process would take two to three weeks, compared with the two to three months needed to drill a relief well.





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