After fixing a leak on a cap designed to plug up the Gulf of Mexico oil spill, BP engineers readied Thursday to see if the new top is enough to contain the gusher.
Kent Wells, a BP PLC vice president, said at a news briefing in Houston that the leak, which was discovered late Wednesday, was fixed by replacing the pipe called a "choke line" on the side of capping device. The work set back the testing process on the cap's capabilities.
The test will involve closing off all three openings in the cap to the Gulf, in theory stopping the oil leaking into the Gulf. BP will be monitoring pressure under the cap. High pressure is good, because it shows there's only a single leak. Low pressure, below 6,000 pounds per square inch or so, could mean more leaks farther down in the well.
BP expects to keep the oil trapped in the cap for 48 hours before it decides if the approach is working.
The cap — a 75-ton metal stack of lines and valves — was lowered onto the well on Monday in hopes of either bottling up the oil inside the well machinery, or capturing it and funneling it to the surface.
Now that the new choke line is in place, BP has to start from a few steps back to resume the process of testing the cap's ability to shut off the flow of oil to the Gulf.
"We're going to keep moving forward with this," Wells said.
It has to once again stop the collection of oil from surface vessels, which resumed after the leak was discovered. For the tests, all the oil has to be trapped under the cap to measure how much pressure it generates.
Then, BP has to recheck equipment used in the test and move undersea robots that perform the work back into position. Wells was hesitant to give a firm timeframe for when the test could start, but expected it to be Thursday, possibly late in the morning.
"Bear with us," he said.
Retired Coast Guard Adm. Thad Allen, the Obama administration's point man on the disaster, said a committee of scientists and engineers will monitor the results and assess every six hours, and end the test after 48 hours to evaluate the findings.
"I was gung-ho for this test and I remain gung-ho for this test," he said Wednesday.
If the cap works, it will enable BP to stop the oil from gushing into the sea, either by holding all the oil inside the well machinery like a stopper or, if the pressure is too great, channeling some through lines to as many as four collection ships.
Allen said the testing will also offer insight into the other, more permanent solution to the fix: two relief wells intended to plug the gusher from deep underground. The mapping of the sea floor that was done to prepare for the well cap test and the pressure readings will also help them determine how much mud and cement will be needed to seal off the well.
Drill work was stopped on one relief well because it was not clear what effect the testing of the cap could have on it. Work on the other relief well had already been stopped according to plan.
The government estimates 1.5 million to 2.5 million gallons are leaking every day.
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