HOUSTON // A larger, tighter-fitting containment cap was installed yesterday atop BP's ruptured wellhead on the floor of the Gulf of Mexico in a move the British energy giant said it hopes will fully contain the deep-sea oil gusher. Crude oil continued to spew into the sea for the time being, but BP said it planned to begin testing the new cap, and the internal pressure of the well, today by closing off valves on the device to constrict the flow of oil.
If the test goes as intended, it would mark the first time since the April 20 explosion and blowout of the Deepwater Horizon drilling rig that the flow of oil from the crippled well has been halted, at least temporarily. But BP, in a statement announcing the installation of the new cap, warned that success was not certain. "It is expected, although cannot be assured, that no oil will be released to the ocean for the duration of the test," the statement said. "This will not, however, be an indication that flow from the wellbore has been permanently stopped."
BP said it does not expect to plug the undersea geyser for good before mid-August, after intercepting the rupture point with one of two relief wells now being drilled. The former US Coast Guard Admiral Thad Allen, overseeing the US government's spill response, said that if the cap works it will be used to resume the siphoning of oil to ships on the surface until the ruptured well can be permanently plugged.
The new cap-and-seal stack, which is larger than the one removed on Friday and bolted over the top of the wellhead rather than clamped loosely over it, is designed to capture three times more leaking oil, or virtually the entire flow. In the meantime, Mr Allen said it was possible that the new cap could be used to shut down the wellhead again temporarily "for a period of time, such as during a hurricane or bad weather."
Doug Suttles, BP's chief operating officer of exploration and production, suggested in a separate briefing that the cap might be used to keep the well closed for a longer stretch. "Depending on the results, we'll either continue to contain the flow while we wait on the relief well or potentially be able to close the flow in," he said. For the duration of the well-integrity tests, two other sub-sea oil-siphoning systems, one of them just brought online as of yesterday, will be turned off, BP said.
Mr Suttles stressed that even if the cap can shut off the flow a 1,600 metres below the surface, BP must still finish the relief well at an even greater depth so it can pump heavy drilling fluid and then cement to permanently plug the leak. Yesterday, the first of two relief wells, begun on May 2, was about 58 metres from intersecting the blown-out well that is 3,960 metres beneath the seabed, Mr Suttles said. The relief well could reach its target by the end of July, BP says, keeping it on schedule to actually kill the leak by mid-August.
If the relief wells fail, BP could install a new permanent oil-capture system by late August or early September, Kent Wells, senior vice president of exploration and production, told president Barack Obama's commission investigating the spill. * Reuters
