BP PLC said Saturday that it has begun an attempt to remove the drilling pipe from the ruptured well that unleashed the Deepwater Horizon spill.
The attempt, which began Saturday morning, follows the successful completion of a 48-hour ambient pressure test, in which the company determined that if the sealing cap and the blowout preventer that sit atop of the well are removed, no oil or gas will come out. BP aims to remove 3,500 feet of drilling pipe before it can proceed to remove the blowout preventer and replace it with a new one.
The head of the federal oil spill response effort, retired U.S. Coast Guard Admiral Thad Allen, ordered BP to produce a plan to fish out the blowout preventer. In a letter released Saturday, Allen said that BP must by Sunday let the U.S. government know how it can remove the sealing cap and blowout preventer while keeping them sufficiently intact for investigators trying to assess the cause of the explosion that killed 11 and unleashed the worst offshore oil spill ever. U.S. officials "will take custody" of all equipment, Adm. Allen said.
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The replacement of the blowout preventer is necessary, U.S. officials said, because there are concerns that the operation that is designed to permanently kill the well could endanger a cement plug that has capped the well since early August. The operation, known as the "bottom kill," would inject mud and drilling cement in the area between the drilling pipe and the surrounding rock formation, known as the annulus. If pressure in the annulus increases rapidly, it could make oil trapped within blow through the cement plug at the top of the well.
Once BP places the new blowout preventer atop the well, the company will proceed to drill a relief well that will intersect the damaged well near its bottom. From there, it will inject the mud and cement, marking the official end of the Deepwater Horizon spill. However, clean-up operations around the Gulf Coast, as well as environmental controversy about the ultimate effects of the release of about 4 million barrels of crude into the ocean, are likely to last for months.
The oil flow has been shut in since mid-July, when BP installed the sealing cap atop of the well. In early August, it pushed the oil back into the reservoir by injecting mud and cement from the top.