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Wednesday, July 18, 2018

Maritime Logistics Professional

Methane hydrate

Posted to Maritime Musings (by on May 18, 2012

A little-known potential energy source.

Methane hydrate (also called methane clathrate or fire ice) is a naturally occurring compound in which methane is trapped inside a water crystal.  Clathrate is a technical term for a solid material in which one component is enclosed in the structure of another.  The material is sometimes called “fire ice” because that resembles a partially-melted lump of ice.  When ignited, the methane burns, leaving liquid water behind.  While methane hydrate was created in a laboratory in 1810, it was thought to naturally form only in the outer reaches of space where temperatures were extremely low.  In the 1960s, though, deposits of methane hydrate were discovered in the seabed.  Substantial deposits have been found under the Gulf of Mexico and the Caspian Sea.  Large deposits also exist in the polar regions.  At one time, there was speculation that the total amount of methane hydrate deposits worldwide might exceed the amount of all other fossil fuels combined.  Closer examination, though, has shown that the amount of methane hydrate reserves, while substantial, are not nearly that large.  It may, though, exceed the reserves of gaseous methane.  Methane hydrates appear to be derived from two separate sources.  The most common form of methane hydrate was derived from microbial reduction of carbon dioxide at low temperature and high pressure under the sea floor.  The second type is thought to have been formed in deep sediments subsequent to the development of methane by thermal decomposition of organic matter.  To date, there is only one commercial methane hydrate field in operation, in northern Russia.  Experimental work has been done in Canada and, most recently, in Alaska to develop the technology to extract methane hydrates in commercial quantity, but it is unclear when commercial operations can actually begin on a large scale.  Methane hydrate made the news during the response to the Deepwater Horizon oil spill.  BP lowered a dome over the wellhead to capture the escaping crude oil and pipe it to the surface.  Unfortunately, the escaping fluid included significant amounts of methane.  Because of the low temperate on the sea floor and the sudden reduction in pressure as the fluid left the well bore and entered the dome, methane hydrates were spontaneously formed.  The hydrates clogged the pipe and obstructed the flow.

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