NEW ORLEANS — The best hope for stopping the flow of oil from the blown-out well at the bottom of the Gulf of Mexico may be using a drill to hit a target the size of a dinner plate more than two miles into the earth. It is anything but a sure bet on the first attempt.
Bid after bid has failed to stanch what has already become the nation's worst-ever spill, and BP is readying another attempt as early as Wednesday, this one a cut-and-cap process to put a lid on the leaking wellhead so oil can be siphoned to the surface.
But the best-case scenario of sealing the leak is two relief wells being drilled diagonally into the gushing well — tricky business that won't be ready until August.
"The probability of them hitting it on the very first shot is virtually nil," said David Rensink, incoming president of the American Association of Petroleum Geologists, who spent most of his 39 years in the oil industry in offshore exploration. "If they get it on the first three or four shots they'd be very lucky."
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For the relief well to succeed, the bore hole must precisely intersect the damaged well. If it misses, BP will have to back up its drill, plug the hole it just created, and try again.
The trial-and-error process could take weeks, but it will eventually work, scientists and BP said. Then engineers will pump mud and cement through pipes to ultimately seal the well.
As the drilling reaches deeper into the earth, the process is slowed by building pressure and the increasing distance that well casings must travel before they can be set in place.
Still, the three months it could take to finish the relief wells — the first of which started May 2 — is quicker than a typical deep well, which can take four months or longer, said Tad Patzek, chair of the Petroleum and Geosystems Engineering Department at the University of Texas-Austin. BP already has a good picture of the different layers of sand and rock its drill bits will meet because of the work it did on the blown-out well.
On the slim chance the relief well doesn't work, scientists weren't sure exactly how much — or how long — the oil would flow. The gusher would continue until the well bore hole collapsed or pressure in the reservoir dropped to a point where oil was no longer pushed to the surface, Patzek said.
"I don't admit the possibility of it not working," he said.
A third well could be drilled if the first two fail.
"We don't know how much oil is down there, and hopefully we'll never know when the relief wells work," BP spokesman John Curry said.
The company was starting to collect and analyze data on how much oil might be in the reservoir when the rig exploded April 20, he said.
In the meantime, BP is turning to another risky procedure federal officials acknowledge will likely, at least temporarily, cause 20 percent more oil — at least 100,000 gallons a day — to add to the gusher.
Using robot submarines, BP plans to cut away the riser pipe this week and place a cap-like containment valve over the blowout preventer. On Monday, live video feeds showed robot submarines moving equipment around and using a circular saw-like device to cut small pipes at the bottom of the Gulf.
The company hopes it will capture the majority of the oil, sending it to the surface.