Home > Physics > How to Plug an Oil Leak with Corn Starch

How to Plug an Oil Leak with Corn Starch

NASA'S Terra Satellite captured this image of the Deepwater Horizon oil slick on May 24, 2010. (Photo: NASA/GSFC)

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One of the biggest, if not THE biggest news story of 2010 was the Deepwater Horizon oil spill. The spill released over 200 million gallons of crude oil into the Gulf of Mexico and is one of the biggest man-made natural disasters in history.

The spill lasted for nearly 3 months due to the high difficulty of plugging the well. One such attempt to plug the leak was the “top-kill” method, which involves releasing a heavy fluid (“mud”) into the well in hopes that it would sink to the bottom and stem the flow of oil. BP’s attempt at this failed, and a paper published online yesterday in Physical Review Letters entitled “Viscoelastic Suppression of Gravity-Driven Counterflow Instability” explains why, and how they could have done better.

So you can imagine the problem like this: you have a well gushing oil upwards. You want to slow down this flow of oil, so you release a dense fluid down into the well and hope it will flow downwards, against the pressure of the oil.

When two different fluids come into contact at different velocities it generates turbulence at the interface. This is called the Kelvin-Helmholtz instability. You have seen it before when you look out onto the ocean or a body of water and the wind creates ripples and small waves on the water. Turbulence is being generated at the interface of the water and the air causing those ripples.

A similar thing happens when oil meets a dense fluid. If the turbulence generated at the interface of the two fluids is high enough to break the “mud” into tiny droplets, then the top-kill method will fail because the mud simply breaks apart and won’t plug the well.

In this paper, the authors demonstrate a fluid which overcomes the Kelvin-Helmholtz instability under conditions similar to those at the site of the Deepwater Horizon spill.

First, however, they theoretically study the effect of using a typical water-based mud in a top kill method for conditions similar to those at Deepwater. What they found was that a typical mud would not have descended quickly enough into the mud to be effective. In other words, the velocity of the oil shooting up the well was much greater than the rate at which the mud would have descended into the oil, resulting in the mud simply being washed out of the well. This would explain why BP’s top-kill attempt had failed.

The authors then tested their own recipe for a mud which may have worked. They introduced a “dilatant polymer with shear-thickening and viscoelastic properties”. What this means is they added a material which would actually get harder under stress (shear-thickening) and resist breaking apart when in contact with the oil. In fact, the force of the oil moving upwards is what would cause it to get harder.

A fluid like this is made of a corn-starch water emulsion. Under high shear stress this fluid gains a “tramponlinelike” behaviour, helping it resist the turbulent flow of the oil.

To test their fluid, they “filled a transparent column 1.6 m tall and 63 mm in internal diameter with a transparent light mineral oil”. They then released their mud into the oil and observed the effects. Using a plunger they simulated the movement of oil over the mud. They found that their corn-starch mixture did not break apart and descended as a coherent “slug”.

The also found that the slug descended at a rate fast enough that it would have overcome the upward velocity of the oil from the Deepwater well. However, they did note that the experiment would have to be repeated at a larger scale to gain a better idea if this would be a useful approach for an actual oil spill.

Beiersdorfer, P., Layne, D., Magee, E., & Katz, J. (2011). Viscoelastic Suppression of Gravity-Driven Counterflow Instability Physical Review Letters, 106 (5) DOI: 10.1103/PhysRevLett.106.058301

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  1. Justa Commenter
    February 1, 2011 at 11:15 pm

    This is a bit of a rheological tangent, but I was wondering what is a good repository for finding data about these sorts of materials. I was particularly interested after hearing that silly putty will shatter with a high enough impact.

    I am interested in maximizing or controlling this tendency in order to improve impact safety devises such as helmets. I was thinking the explosion from the shatter would be able to disperse a lot of force diffusely (like a car’s crumple zone). After the collision, the material would return to its fluid properties, allowing it to be collected and the shatter zones re-set, at which time helmet could be re-used.

    I don’t have the time or lab to do a bunch of experiments but I would be willing to do calculations.

    • February 3, 2011 at 2:28 pm

      I can’t say I know of a good online resource for such information. However if you live near a University you can probably get a public membership to their library. There would be a wealth of information on materials science there.

  1. February 2, 2011 at 1:02 pm

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