14 May 2010

New Estimates of Oil Leak Rate Stoke Widespread Hysteria

New media estimates of leakage rates from the Deepwater Horizon seafloor gusher range from 20,000 barrels per day up to 100,000 barrels per day. These estimates were hastily arrived at by various remote methods by a number of academics: a mechanical engineer at Purdue, an astrophysicist at Berkeley, an oceanographer at Florida State University, and others who are willing to go on record with a public estimate. The official NOAA estimate of the leak rate remains constant at 5,000 barrels per day.

These new inflated media estimates of the leakage flow rates are having the desired rate of ramping up public concern -- in the cases of some online commenters, outright panic. Here are a few articles reporting the newer, higher leakage estimates:
LA Times
Denver Post
The Guardian

According to the new estimates, the Deepwater Horizon marine spill has already eclipsed the Exxon Valdez disaster in volume of oil released, and may have even made the top ten list of all time marine spills.

But are these estimates credible? Are these huge new estimates compatible with what is seen on the surface of the Gulf? Do we see many times the environmental damage as was seen from the Exxon Valdez?

If the Deepwater Horizon gusher has been spewing 100,000 barrels a day for the past 24 days, it would have released 2.4 million barrels of hydrocarbon, or about 100 million gallons (roughly 300,000 tons).
The distribution of oil spilled on the sea surface occurs under the influence of gravitation forces. It is controlled by oil viscosity and the surface tension of water. Only ten minutes after a spill of 1 ton of oil, the oil can disperse over a radius of 50 m, forming a slick 10-mm thick. The slick gets thinner (less than 1 mm) as oil continues to spread, covering an area of up to 12 km2 [Ramade, 1978]. During the first several days after the spill, a considerable part of oil transforms into the gaseous phase. Besides volatile components, the slick rapidly loses water-soluble hydrocarbons. The rest - the more viscous fractions - slow down the slick spreading. _offshore-environment
So if one ton of oil spreads to cover an area of 12 km2, 300,000 tons of oil would cover an area of 1.6 3.6 million km2 (or about 600,000 1.4 million sq. miles). The entire surface area of the Gulf of Mexico is 1.5 million km2.

Of course much of the short chain hydrocarbons will have evaporated, and some of the oil has sunk beneath the surface. But dispersants tend to spread the remaining oil across a larger area, somewhat magnifying the apparent area of the slick. In other words, had as much oil been released as is claimed by the mechanical engineer, the astrophysicist, and the oceanographer, would it not be reasonable to assume that virtually the entire Gulf would be covered by now?

Here is the rub: a very large part of the hydrocarbon release is in the form of natural gas, which evaporates into the air straightaway. Without knowing the proportion of gas to oil fairly reliably, one cannot truly predict how much oil is being released by watching (or taking rough measurements of) the seafloor gusher. And the lighter the crude oil, the more quickly the short chain hydrocarbons will evaporate in the warm Gulf waters. So one must also have a good idea of the type of crude that is leaking.

Certainly a couple of oil soaked birds and several dozen rubbery oil clumps washed ashore does not come close to matching the devastation of the Exxon Valdez spill.

If the engineer and scientists being quoted by a ghoulish media were honest, they would admit that their estimations are too crude to be taken seriously. Certainly too crude to be used to drive a national hysteria. But the media is not picky, as long as it gets its story.

Regardless of the rate, the gusher needs to be stopped so that top-side cleanup can be definitively carried out.
BP (BP 46.51, -1.59, -3.31%) attempted to thread a smaller siphoning tube into a larger pipe gushing oil into the Gulf of Mexico early on Friday, according to a company spokesperson in London. It's BP's latest attempt to slow down the oil spill that began on April 22 after the Deepwater Horizon rig caught fire. The company used remote control robots on the sea floor a mile below the surface to move the 6-inch tube into the 21-inch riser pipe, according to a report from the Associated Press. The pipe could be in place on Friday. _Marketwatch
The "siphon tube" approach is not a real solution to the seafloor gusher. It will merely suck up a portion of the oil being spilled. But if it is successful, it may improve the chances of other supplementary seafloor oil recovery approaches. It is certainly an ultra-cautious approach on the part of BP.

Information about the causes of the disaster are slowly coming to light, and there will be plenty of time for judging the actions of those involved. But for now, whatever the rate and composition of oil leak -- it needs to be stopped.

Very little oil washed ashore to date
Louisiana re-opens large fishing area
Attempts to siphon oil flow from seafloor riser continues The "top hat" attempt to cap the main gusher at the BOP will wait until the weekend.

Even More: Times Picayune video update on oil spill:
Oil pill video: Reporters give latest update


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Blogger Loren said...

There was a John Wayne movie about Red or someone like that who put out well fires. One thing I remember while reading this is that after putting the fire out, the top of the well was set up so that a new emergency valve could be very quickly bolted on and closed--pretty much immediately in movie time, I suppose it might take up to a couple of hours to do it IRL.

Point is, it really wouldn't be very hard to set this stuff up in a similar manner. The top of the BOP could be drilled and threaded for a similar device, and the bottom could be set up so that if you really wanted to, the BOP could be removed and replaced. The two problems with this are the pressure, and the ROVs--it seems they don't have many designed to be able to put "oomph" behind their work, limiting their usefulness in manhandling things.

You could also make a self-threading riser valve--cut the riser off a few feet from the BOP, fit it over, and screw it on before closing the valve. Again though, you'd need to be able to manhandle the thing through the high pressure oil flow--something I get the impression the current ROVs can't do.

I've been wanting to study robotics, perhaps a "Superman" deep sea ROV would be a good project.

Saturday, 15 May, 2010  
Blogger al fin said...

Right. Better to prevent the problem to begin with, or to build into the technology the means to stop the disaster before it goes too far.

A submersible super-robot would be a great idea.

Unfortunately, human problem-solvers are too often driven by need for disaster mitigation, rather than disaster prevention.

Powerful robots on the seafloor would need anchor points to operate from. Deep anchors drilled into the rocks would allow the super-robots the leverage they would need to fight against strong well pressures.

Surround the wellhead by these deep-rock anchors before you even start drilling.

Or another approach would be to shove a large tampon deeply into the gushing well. Certainly tampons plug a lot of plumbing drain lines from houses and commercial buildings, so why not an oil well?

These tampons would need to be designed to expand from the absorbtion of hydrocarbons, and would have circumferential "barbs" that would allow only one-way penetration down into the well casing. Perhaps a robotic tampon that wiggled its way down the pipes, streamlined against pressure.

Sunday, 16 May, 2010  
Blogger cap vandal said...

I am disturbed by the irresponsibility of the media in trying to fan hysteria about the oil leak.

Right now, BP has stated that they are sucking up 3,000 bbls/day and flaring off 14 million cubic feet of gas. They also say that the visible oil at the surface has been significantly decreased.

If one is to believe BP, that would tend to support an estimate of 5,000 bbls/day or perhaps 10,000 bbls/day.

However, there is another way to look at the estimate. If this were not a blowout, 5,000 bbls/day would be a monster well.

There are 5,000 oil leases in the gulf, and we produce about 1.3 million bbs/day of oil.

The new, almost 100,000 bbl estimate by the Perdue guy would be 8% of ALL OIL produced in the Gulf.

The original estimate was by NOAA, not BP.

BP's argument is that their containment strategy is not dependent on the amount of oil leaking -- that is, they are going all out to contain it. Therefore the estimate is irrelevant to their containment strategy.

I don't see how BP gains anything by misrepresenting the size of the leak.

The high estimates are simply sensationalism.

Thursday, 20 May, 2010  

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