A mixture of cornstarch and water best known for entertaining kindergartners could have plugged the spewing Macondo oil well in the Gulf of Mexico, say physicists.

Where regular drilling mud failed to stop the flow, oobleck — a complex fluid that seems to switch between liquid and solid — succeeded in simulations published Jan. 31 in Physical Review Letters.

“We couldn’t do a full scale experiment on a real well that was blowing out 50,000 barrels a day, but to the extent that you can do a smaller experiment in the laboratory it’s basically the same physics,” said physicist Jonathan Katz of Washington University in St. Louis. “And it seems to work.”

Last May, three weeks after an explosion on the Deepwater Horizon drilling rig left an open well gushing thousands of barrels of oil into the Gulf, the Department of Energy convened a group of independent experts to help stop the flow.

BP, which owned the well, planned to pump heavy drilling mud into the well in a project called “top kill.” The plan was for dense mud to sink through the oil and clog the bottom of the pipe. Top kill had worked for other blowouts, where the oil flowed more slowly. But the DOE group saw almost immediately that for Macondo, top kill would fail.

Like paint or ketchup, mud used in drilling thins when it flows quickly, Katz explained. Usually that’s an advantage, because thinning mud is easier to pump into a well. But if the oil comes out too fast, and two fluids with different densities rush past each other, turbulence takes over. Whorls and eddies form.

Oil gushed out of Macondo at 3.7 meters per second, causing enough chaos to break up the mud into tiny, useless droplets. “It was sufficiently fast to break up anything descending into small droplets, and sweep them back up and spit them out the top,” said Katz, who was part of the DOE team. “That’s what ruined the top kill.”

But even as BP made plans for its doomed top kill, Katz wondered whether oobleck might do the trick.

The half-water, half-cornstarch goop is named after the Dr. Seuss book Bartholomew and the Oobleck, and its quick-change artistry between liquid and solid makes it a kitchen science classic. When it’s flowing slowly, oobleck can drip through your fingers as a liquid. But when oobleck flows quickly, it turns suddenly thick, almost solid. YouTube is full of people running across pools of oobleck, and sinking when they run too slowly.

Katz did some quick math and saw that a half-cornstarch drilling mud would suppress the turbulence and sink in one coherent slug. Unfortunately, no one listened.

“I have no idea why they didn’t pay attention,” said Richard Garwin, a retired IBM physicist who was also part of the DOE-convened team.

The top-kill plan went ahead with the usual drilling mud, and ultimately failed. But Katz went on to team up with Peter Beiersdorfer, David Layne and Edward Magee of Lawrence Livermore National Laboratory to test whether oobleck might really have worked.

The researchers filled a tube 1.6 meters tall and 63 mm in diameter with a transparent mineral oil. They pumped water colored with green dye into the oil at a rate of about 1.15 meters per second, and saw the swirling turbulence they expected.

But when they repeated the experiment with a mixture of cornstarch and water, the goop sank in a single column.

The new paper is “an excellent piece of work,” Garwin said. “It should have been done by BP long ago.”

Engineer Paulo Arratia of the University of Pennsylvania thinks the experiment is a very good first step, but he would like to see a more systematic follow-up study. “It works in a bench-top experiment, in the lab. I don’t know if it works in the real oil well,” he said.

In particular, he would like to see more details on the physical properties of the oobleck: how fast it flows, how quickly it switches from liquid to solid, and which kind of cornstarch they used.

“This will not be the last time we have oil spills,” he said. “It will be very important to know if this is actually a valid method. Come [the next] disaster, we’ll need to know exactly what we’re dealing with.”

Images: 1) Flickr/thatmushroom. 2) Physical Review Letters/Beiersdorfer et al. 2011. Video: Michigan Technological University

“Viscoelastic Suppression of Gravity-Driven Counterflow Instability.” P. Beiersdorfer, D. Layne, E.W. Magee and J. I. Katz. Physical Review Letters, Vol. 106 No. 5, Week ending Feb. 4, 2011. DOI: 10.1103/PhysRevLett.106.058301



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