Two Mysteries Surround Gulf Oil Spill ...

Eli is a contributing correspondent for Science magazine.

This morning, officials raised their estimate of the amount of oil spilling out from the destroyed Deepwater Horizon rig in the Gulf of Mexico from 1000 to 5000 barrels per day. But how much oil will ultimately reach the shore of the gulf is only one of the questions that officials now face.

Oil companies have been drilling in ocean depths of approximately 1525 meters for more than a decade, but there's never before been an accident like the one that occurred on 20 April. The essential problem was a so-called "blowout"—an explosive release triggered when the oil and gas under high pressure in the well beneath the surface exceeds the pressure of the machinery trying to tap it. In this case, the gusher caused a deadly fire (now extinguished) and a continuous oil spill that is spreading over the surface of the ocean toward the Louisiana coast.

There's a ton of speculation as to why the original accident occurred when it did, (some helpful guesses on that). Experts say they just don't know for sure. But an even more important question is why a series of valves in the 450-ton "blowout preventer" (BOP) failed to close off the gusher after it began. The BOP, which sits on the sea floor, can close off any gushing well in several ways—such as by plugging a pipe or even by crushing it horizontally like squeezing a straw until it is cut off. A key piece of machinery, the BOP is usually tested regularly, even daily.

"The industry and academia are continuously improving the technology, and even though an accident like this is extraordinarily rare, we cannot let this happen again," says Paul Bommer, a professor of petroleum engineering at the University of Texas, Austin. One of the first tasks will be to investigate why none of the four ways to activate the BOP has worked.

Normally, hydraulic equipment controlled by engineers up on the oil rig can close the BOP. As a backup, most BOPs have automatic shutoff valves known as "Dead Man" switches that cause the BOPs to close automatically if there is loss of communication from the oil rig. As another backup measure, many BOPs have radio-controlled switches to allow crews to close the valve remotely—but the Deepwater Horizon lacked that device. So now, as the oil continues to pour out of the open well nearly 1.5 kilometers below the ocean surface, engineers are desperately trying to close the BOP manually using an arm on a robotic submersible.

If the BOP can't be properly activated, oil companies and the government are racing to deploy two other solutions, but they will each take a long time. The first is to drill a new well into the oil reservoir out of which the gusher is flowing. Cement or other hardening material could then be added to the reservoir to stop the flow, which could take as much as 3 months, says BP, who owns the rig. The second solution is to build a giant underwater tent to contain the oil as it's released, but that could take a similar amount of time.

If the new estimates of 5000 barrels of oil a day are correct, it will take less than 2 months for the amount of oil spilled out to equal the total amount of oil released in the Exxon Valdez tragedy, 260,000 barrels.

For more on the gulf oil spill, see our full coverage.

Posted in Climate gulf oil spill, oil fate