Social science guy needs physical science info

July 4, 2010 9:23 PM

Please help me understand the BP oil spill. I see the footage of the oil plume and wonder how wide it is when it reaches the surface. This question tells me why capping the pipe is not feasable. But what about creating a thermal column of warm(er) water to help "focus" the oil plume to a more concentrated area on the surface while the relief well is being drilled? Thanks for your explanations...
posted by DB Cooper to science & nature (10 answers total)

The ocean is a huge heat sink. There's no way that any man made process can create thermal currents. Consider the amount of energy it would take to raise a 1 meter square column of water by one degree: at a depth of 1500 m that's 1.5 million kg of water, which means you'd have to dump 1.5 MJ of energy into it nearly instantly to raise it one degree (over 1 second that's 1.5 MW) and even after doing all that it would simply dissipate to diffusion in a few seconds as the surrounding water absorbs the heat.
posted by Rhomboid at 9:48 PM on July 4, 2010 [3 favorites]

(oops, and I even bungled the specific heat of water which is 4.2 J/(g*K) so my numbers are about 240 times too small.)
posted by Rhomboid at 10:06 PM on July 4, 2010

And even if you did, that's not how turbulence works. Making the jet move faster would cause it to create more and bigger whorls which would spread out further.
posted by Chocolate Pickle at 11:15 PM on July 4, 2010

It's easier to put a pipe-end with a flexible hose attached to it to channel the oil to the surface. Accomplishes the same thing I believe except without the complex physics and energy requirements of a vertical curtain of moving water.
posted by zippy at 11:46 PM on July 4, 2010

Er, the pressure at 1500 m is about 150 times atmospheric pressure (2200 pounds per square inch) so I don't think anything flexible or hose-like is going to last long there. Remember this is far below crush depth of any submarine. (Unless I've misunderstood what you were describing...)
posted by Rhomboid at 1:55 AM on July 5, 2010

isn't the pressure inside and outside the hose going to be the same?
posted by mary8nne at 8:04 AM on July 5, 2010

Things like this have been tried before. The most sucessful is a barrier of air bubbles, but that's only effective down to 2-3 meters.

Also, as Rhomboid says, you would need a major power plant or two to make this efective. Don't forget also that heat is pollution too. An increase in water temperature of even a couple of degrees is enough to start killing the ocean. A large rise in temperature could sterilize it.

Even so, as Chocolat Pickle says, that wouldn't help matters much. Bubble turbulence causes a lot of mixing---it's three phases: oil, water and methane gas. Right now, the plume rise angle is roughly 45 degrees. At a mile down, it spreads out into a circle about one to one and a half miles on the surface.

Furthermore, the dispersant application at the top of the BOP creates smaller oil droplets. These take longer to rise (following a modified Stoke's Law). This spreads out the rise area even more causing a dispersed oil tail. Dispersant application is the major factor reducing oil coming ashore in the CG's view. They're not going to stop using it.

isn't the pressure inside and outside the hose going to be the same?

No. Water pressure at that depth is ~2500 psi/160 atmospheres (and about 4C). The oil is coming out at ~5000 psi/330 atmospheres (and at 150 C). The hose has to capture that pressure. Normal riser pipe is steel about 1" thick.
posted by Anonymous 5$ Sockpuppet at 10:17 AM on July 5, 2010

Thanks for the explanations everyone.

Rhomboid and Anonymous 5$ Sockpuppet: Any "thought experiments" on how the damages could be mitigated while waiting for the relief well? Like instead of trying to heat cold water to rise --would pumping a ring of cold water from depth to warmer surface take less energy, avoid added heat pollution, and create a barrier curtain of sinking water?

Any other way to focus the plume until it gets into warm enough water to not clog an intake dome with ice crystals?

Or helping contain the surface spread of the oil spot with a screw-like, inward rotating spiral of boom & boats?

Leprechauns?
posted by DB Cooper at 11:45 AM on July 5, 2010

Require the oil companies to have relief wells drilled to 95% of completion before they can open the main well.
posted by Rhomboid at 6:56 PM on July 5, 2010

Which would approximately double the cost, with all that implies.
posted by Chocolate Pickle at 1:36 PM on July 6, 2010