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Earth

BP’s vain efforts to stem the oil leak

Text by Sébastian SEIBT

Latest update : 2010-07-19

Since April 26, oil giant BP has made several, increasingly-desperate attempts to stop oil gushing out of a stricken well in the Gulf of Mexico. FRANCE 24 takes a look at the different stages of a dramatic race against time.

The failure of BP’s "Top kill" operation in the Gulf of Mexico has raised alarming questions. Just how many more attempts, and months, will it take to stop the leak?

The White House fears the dangerous spill will continue unchecked at least into August, but acknowledges it can only play a supporting role in BP's dramatic race against time. So what has the BP done so far and why has it failed?

April 26: BP’s first spill-stopping mission involves sending four robots 1,500 metres below sea level to close the well’s safety valve, known as a blow-out preventer. The machines have been in use for decades, but never at this depth.

By the time BP announces the operation, the robots have already been at work for several days – to no avail.

The oil company soon acknowledges its failure and announces that its engineers are frantically constructing a giant dome that will be placed over the leaks to trap the oil. BP says this will enable it to pump the oil up to container ships on the surface.

May 8: A 98-ton, four-story containment dome is lowered underwater. Again, it is the first time in history the device has been used at such depth.

Experts warn that the dome could inadvertently accelerate the flow of the leak. But before it even reaches its target, methane hydrates crystallise on the dome, effectively rendering it useless. BP pulls the dome back to the surface.

May 12: A second containment attempt is made with a smaller version of the dome, which BP dubs the "Top hat".

The smaller dome, which contains less freezing water, is successfully lowered to the ocean floor. But BP decides not to use it, opting instead for an insertion pipe it believes will help recover the oil faster.

May 13: The dome strategy is ditched and BP goes ahead with plans to insert a pipe, measuring 15 cm in diameter and 1.5 km in length, into the broken well. Three days later, BP says it has finally managed to pump out some oil; but only 20 percent of the crude gushing out into the sea.

In the meantime, the growing slick has prompted mouting anger among the public and officials in Washington. BP goes back into the huddle and returns with a secret weapon.

May 26: The oil company’s engineers unveil operation "Top kill", which many see as a last-chance opportunity to save coastlines. BP pours a heavy fluid composed of water, barite (a mineral) and then cement through two pipes leading to the well’s valve.

BP says the "Top kill" has a 60 to 70 percent chance of success. At first, the strategy seems to work. But four days later BP says the cement has given in to pressure from the leak.

May 31: Strategies to stem the flow of oil are discarded. In its latest plan, BP opts instead to cut away the leaking riser pipe and then cap it with a rubber seal to capture the leaking oil.

BP says it does not expect to fully seal the leak until relief wells can be built to divert a considerable amount of the oil -- but the wells won't be ready before August.

June 2: BP makes a successful first cut on the riser pipe, but a diamond-tipped saw blade brought in to make a second “clean” cut gets stuck in the pipe. BP later dislodges the blade.

June 3: BP drops the diamond saw and returns to the idea of using a “Top hat” to send trapped oil to the surface.

June 4: Engineers lower a containment cap onto the ruptured wellhead after finally meeting success in their attempt to cut off part of the leaking pipe.

June 7: The oil major says the containment cap is capturing “about half” the oil spilling into the Gulf.

July 10: BP engineers use underwater robots to place an improved containment cap over the ruptured oil well. BP hopes that the new, larger cap could quickly be trapping all of the oil currently being released into the Gulf.

July 15: BP announces it has stopped the flow of oil into the Gulf of Mexico for the first time since April, after shutting down the last of three valves on the new containment cap.

Date created : 2010-06-04

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