The BP Well Operation and Their Problem with 'ice' Clogging

Image source: unknown

British Petroleum engineers have successfully installed a cover on the leaking well and are trying to siphon oil to surface ships.  They have been proceeding cautiously because their previous attempt with this procedure got clogged with a nasty form of ice called "methane hydrate" or "methane clathrate".

Water ice is capable of absorbing an amazing amount of some gases into its structure in "cages".  A typical clathrate cage is shown in the inset of this image of a methane clathrate burning.  Yes, you can set ice on fire!. The gas burns off leaving the ice structures behind. The gas molecules are stored in cages of H2O molecules, and it's quite amazing how much gas can be stored in these cages.

Clathrates are a major reservoirs of natural gas globally, as shown by the map of clathrate deposits.  The dissociation of this weird form of ice has been implicated in everything from the disappearance of ships in the Bermuda Triangle to sudden climate change.  It's been proposed that sudden "burps" of methane gases from clathrates in the Bermuda Triangle have changed the density of the water column so that ships that were floating on the water suddenly found themselves floating on "gassy water" and lost buoyancy, sinking to the bottom. (One thing nice about this blog is that I don't have to provide rigorous referencing!!)  55 million years ago, the Paleocene/Eocene boundary, there was a dramatic climate change that some have argued was due to a sudden methane influx into the atmosphere due to decomposition of clathrates.  The cause of decomposition is unknown, but theories relevant to the current climate crisis are abundant.  I found this article by Galvin Schmidt to be a thoughtful analysis.

Gulf of Mexico Natural Oil Seep Rate vs. Deepwater Horizon Seep Rate

Photo from BP via Reuters, published in NYTimes.com on June 2, 2010

I will rarely post a fairly lengthy direct quote here, but this one is worth it and from an expert, Cutler Cleveland. He was a student of Bruce Hannon's here, and is a professor at BU. We used his sustainability text in our sustainability course.

First published in the Encyclopedia of Earth
------
"Some reports in the media attempt to downplay the significance of the release of oil from the Deepwater Horizon accident by arguing that natural oil seeps release large volumes of oil to the ocean, so why worry? Lets look at the numbers.


Natural seeps can be thought of as natural springs from which liquid and gaseous hydrocarbons (hydrogen-carbon compounds) leak out of the ground. Oil seeps are fed by natural underground accumulations of oil and natural gas. Satellite images have identified hundreds of areas where oil is likely to seep from the Earth's crust into the waters of the Gulf of Mexico. These seeps occur over a wide range of the 615,000 mi² (1.6 million km²) Gulf. A 2003 study by the National Research Council and a 2009 report by oil spill expert Dagmar Schmidt Etkin indicate that between 560,000 and 1,400,000 barrels per year (1,534 to 3,835 barrels per day) seep into the Gulf of Mexico from natural sources. Dozens of natural seeps have been identified off the coasts of Louisiana and Texas, some in the region of the Deepwater Horizon site.


These natural seeps are quasi-continuous or chronic inputs that represent a "background" rate of oil input that have been in existence for hundreds or thousands of years. As the term "seep" implies, the rate of oil release from these sources is much smaller than human spills that often release large, concentrated pulses of oil. One of the largest and most intensively studied seepage areas lies off Coal Oil Point, in Santa Barbara County, California. Individual seeps in this area release an estimated 80 to 100 barrels (3,360 to 4,200 gallons) of oil per day; Deepwater Horizon is releasing 12,000 to 19,000 barrels per day.


The Deepwater Horizon site releases 3 to 12 times the oil per day compared to that released by natural seeps across the entire Gulf of Mexico. By May 30, the Deepwater Horizon site had released between 468,000 and 741,000 barrels of oil, compared to 60,000 to 150,000 barrels from natural seeps across the entire Gulf of Mexico over the same 39 day period.


Natural seeps are not constantly active; the volume of oil released can vary considerably throughout the day and from day to day. As a result, only a small area around the source is actually exposed to "fresh" non-degraded oil, which is its most toxic state.


Marine and coastal organisms and ecosystems presumably have adapted to the natural rate of oil input. Indeed, most organisms living in the regions near natural oil seeps have no special adaptations to the oil. Researchers at Woods Hole Oceanographic Institute and the University of California/Santa Barbara studied natural seeps off the coast of California. They found that as the oil moved upwards in the water column, a wide range of microbes consume the oil and produce intermediate products, and that those intermediate products are then converted by another group of microbes to natural gas and other compounds. Their research suggests that oil from natural seeps normally stays in the water for between ten hours to five days.


Oil that does make it to the surface from natural seeps can spread out very widely. One gallon of oil can spread out to cover more than a full square mile, forming an extremely thin film on the surface, about one-hundredth of a millimeter thick. Under these conditions, the oil is not hazardous. Some of the oil in that thin sheen evaporates within seconds or minutes after it reaches the surface.


A sudden, concentrated and massive pulse of oil from an event such as the Deepwater Horizon disaster presents a fundamentally more acute stress to marine and coastal systems. The amount, rate and spatial concentration of crude oil released from such an event overwhelm the natural mechanisms of oil dispersal and breakdown, producing the significant ecological effects that we observe."

Cutler J. Cleveland
Boston University
May 31, 2010
http://www.eoearth.org/article/Deepwater_Horizon_oil_spill

References


Clester, S.M., J.S. Hornafius, J. Scepan and J.E. Estes, Quantification of the relationship between natural gas seepage rates and surface oil volume in the Santa Barbara Channel, EOS Transactions of the American Geophysical Union 77 (1996), p. 420.


Cutler J. Cleveland (Lead Author); C Michael Hogan and Peter Saundry (Topic Editor);. 2010. "Deepwater Horizon oil spill." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth May 24, 2010; Last revised May 30, 2010; Retrieved May 30, 2010]

Farwell, Christopher, Christopher M. Reddy, Emily Peacock, Robert K. Nelson, Libe Washburn and David L. Valentine, Weathering and the Fallout Plume of Heavy Oil from Strong Petroleum Seeps Near Coal Oil Point, CA, Environ. Sci. Technol., 2009, 43 (10), pp 3542–3548.

National Research Council Committee on Oil in the Sea. 2003.Oil in the Sea III: Inputs, Fates, and Effects. National Research Council Ocean Studies Board and Marine Board Divisions of Earth and Life Studies and Transportation Research Board. National Academy Press, Washington, DC, USA. 265 pp.

Schmidt Etkin, Dagmar, Analysis of U.S. Oil Spillage, API Publication 356, American Petroleum Institute, August 2009, Washington, D.C.

Wardlaw, George D., J. Samuel Arey, Christopher M. Reddy, Robert K. Nelson, G. Todd Ventura and David L. Valentine, Disentangling Oil Weathering at a Marine Seep Using GC×GC: Broad Metabolic Specificity Accompanies Subsurface Petroleum Biodegradation, Environ. Sci. Technol., 2008, 42 (19), pp 7166–7173.

Live video of Gulf Coast Oil Leak is Available

Photo of the platform Deep Water Horizon by U.S. Coast Guard.


BP has released a streaming video of the source of the oil spill in the Gulf of Mexico. Apparently the position of the camera will be changed sometimes so it should be an interesting video to follow.

Striking aspects of the plume are the unsteadiness of the flow, the existence at times of two streams (a light stream, presumably methane gas, and a darker stream, presumably the oil), the turbulence, and the spiraling rotation of the plume. Prof. Steve Werely at Purdue claimed to the Senate last week that he had used PIV to obtain the discharge rate of oil into the Gulf. PIV tracks individual fluid packets in order to estimate velocities. I do not have access to his velocities, but only to his conclusions. He claims that there are 70,000 barrels per day (3.9 million gallons per day), a value way in excess of the 5,000 barrels per day that BP and the US government have been using. He claims that 25,000 barrels per day are coming out of a 1.2" wide pipe. There are apparently 3 sources of oil, but I've not been able to find the details of the geometry. I did some calculations that show that the velocity would be about 1.5 meters per second. This seems like a reasonable velocity to me from the videos that I've been able to see.