Why is BP trying to stop the Gulf of Mexico oil leak with golf balls?

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May 18 2010 7:30 PM

Water Hazard

Why is BP trying to stop the Gulf of Mexico oil leak with golf balls?

What's the best way to plug an oil leak? Click image to expand.
What's the best way to plug an oil leak?

The Macondo well has released more than 5 million gallons of oil into the Gulf of Mexico and continues to spew at least 200,000 gallons per day. A mile-long straw inserted into the well is now directing 40 percent of the flow into tankers, but BP is still looking for a permanent fix. They may try clogging the faulty blowout preventer with shredded tires, knotted rope, and golf balls in a process known as a "junk shot." Wait, golf balls?

You heard me, golf balls. When an oil company taps a well, they place a steel tower over the pipe that leads into the reservoir under the ground or sea floor. This tower, known as a blowout preventer, has a series of valves on its sides and top that can be adjusted to slow or stop the flow of oil. When the Deepwater Horizon rig sank on April 22, its blowout preventer sprung several leaks. In theory, a junk shot would stuff the tower with objects of different sizes, shapes, and textures, so that oil couldn't pass up through these leaks and into the ocean. The junk items would have to be strong enough to hold up against the pressure of the oil, which is gushing out with significant force. (Otherwise, they might be crushed to bits and flow through the leaky valves themselves.) Golf balls happen to be small enough to fill gaps between the rope and tires, and they're very, very sturdy—most are designed to withstand 2,000 pounds of force from a club.

BP might have chosen other types of detritus for a junk shot—there's no reason a bowling ball couldn't be part of the mixture, for example—but with so many junk materials to choose from, you have to start somewhere. Engineers based their first recipes for the junk shot on the one used to quell the 1991 Kuwait oil fires. (No word on whether that one included golf balls or any other sporting equipment.) But more than a week of testing on a replica of the leaky blowout preventer in the Gulf led to the revised set of ingredients.

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BP has already lowered a set of pipes containing the junk to the ocean floor. The garbage is lined up inside the pipes in 10 layers, with the bigger items—the tires and rope—set to enter the blowout preventer first. Then comes the golf balls, the electrical wires, and bits of junk of further decreasing size. That way, the big items will be pushed up against the inner wall of the tower, blocking the smaller stuff from passing through the leaking valves. If all goes according to plan, the golf balls will help stopper the well while themselves being trapped in a net of rope and rubber.

To make all this happen, the junk layers would have to be forced through tubes into the bottom of the tower, where the blowout preventer meets the top of the well. The oil rising from inside the well would then force the garbage up into the top of the tower, where engineers hope it would become lodged and seal the openings. At that point, BP would pump a viscous mud through the same tubes that the junk passed through. With the leaks sealed, the fluid would have no place to go but down into the well. Downward pressure from the fluid would trap the oil in the reservoir and underwater cement could be used to seal the well.

Although tires, rope, and golf balls are the most widely cited ingredients, BP isn't proposing to use household garbage alone. The junk shot would also contain epoxy spheres used in the oil industry to seal tube perforations, called frac balls. These are smaller than golf balls—usually no more than one inch in diameter. There may be other items as well. The company hasn't released the precise recipe.

BP executives have objected to the termjunk shot, but it's a fairly good descriptor of the process. The garbage must be injected with tremendous force, or pressure from the spewing oil would prevent the junk from entering the tower. More than one shot may be required. Engineers have lowered enough junk to the sea floor for two shots, and will reload if necessary.

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Explainer thanks Gerald Graham of World Oceans Consulting and Mark Proegler of BP.

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Brian Palmer writes about science, medicine, and the environment for Slate and Earthwire. Email him at explainerbrian@gmail.com. Follow him on Twitter.

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