Needlessly invoking clathrates. BP’s underwater ice machine.

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In the news reporting on the BP oil spill, there is talk of methane/water forming a special ice composition that defeated the previous attempt to channel oil to the surface.  I think folks are referring to clathrate formation. This ice blocked the flow of petroleum from the concrete structure that was lowered over the well head.

But, here is the deal. Wouldn’t you expect cooling of a compressed gas as it exits the well pipe and into the sea water? Isn’t this just an example of the Joule-Thompson effect?  As the natural gas component of the petroleum discharge exits the pipe, it is going to expand somewhat, even at a one mile depth, and cool the surrounding water. If this occurs in unconfined, open water, the jet of petroleum will entrain water in the flow and be warmed by the continuous flow of heat from the water.

But, if the gas/oil mixture of petroleum is ejected in a confined space that interferes with heat transfer, then one would expect the expansion cooling of the gas phase to predominate and cool the water in the confining space, possibly to the freezing point. Clathrates may be formed, but the simplest explanation is from good old thermodynamics.

1 thought on “Needlessly invoking clathrates. BP’s underwater ice machine.”

  1. Uncle Al


    http://en.wikipedia.org/wiki/Methane_clathrate

    Methane hydrate/clathrate is a nightmare in buried natural gas pipelines. The throughput is molecular sieve dried as hard as they can or the pipe clogs with rock – and woe to the pig sent in to do something about it.

    Water enthapy of fusion is 80 cal/g. Methane hydrate enthalpy of formation is 97 cal/g. Methane to water molar is 1:5.75. It’s a gassy well, 3000:1 methane/oil at STP. Clog city. One imagines BP’s real fear is a crappy cementation job courtesy of Halliburton. Plug the blowout, let full pressure equilibrate, and the whole thing could go like a champagne cork. After the spill is entrained in the Gulf Stream, the entire East Coast fishery will be ravaged. One would need be mad to eat any seafood unless already on the short list for a liver transplant.

    Consider carbon sequestration. Deep aquifer or benthic pumping-dumping of CO2 can form a hydrate clathrate,

    http://en.wikipedia.org/wiki/Carbon_dioxide_clathrate

    Geochemistry tells us wet CO2 is corrosive to silicates over time. Carbon sequestration has all sorts of “unanticipated” bad luck aborning.

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