Sir Humphrey Davy discovered gas hydrates or clatharates in 1810; they are crystalline water based solids physically resembling ice, in which small non-polar molecules (typically gases) are trapped inside "cages" of hydrogen bonded water molecules.

Without the support of the trapped molecules, the lattice structure of hydrate clathrates would collapse into conventional ice crystal structure or liquid water. Most low molecular weight gases (including O2, H2, N2, CO2, CH4, H2S, Ar, Kr, and Xe), as well as some higher hydrocarbons and freons will form hydrates at suitable temperatures and pressures. Clathrate hydrates are not chemical compounds, as the sequestered molecules are never bonded to the lattice. The formation and decomposition of clathrate hydrates are first order phase transitions, not chemical reactions.

Since the 1970s, naturally occurring gas hydrate, mainly methane hydrate, has been recognized worldwide, where pressure and temperature conditions stabilize the hydrate structure. It is present in oceanic sediments along continental margins and in polar continental settings. It has been identified from borehole samples and by its characteristic responses in seismic-reflection profiles and oil-well electric logs. Beneath the ocean, gas hydrate exists where water depths exceed 300 to 500 meters (depending on temperature), and it can occur within a layer of sediment as much as ~1000 meters thick directly beneath the sea floor; the base of the layer is limited by increasing temperature. At high latitudes, it exists in association with permafrost.

It has become increasingly evident that naturally occurring gas hydrates are important components of the shallow geosphere and are of societal concern in at least three major ways: resource, hazard and climate.

Two reasons make gas hydrates attractive as a potential resource. First is the enormous amount of methane that is apparently sequestered within clathrate structures at shallow sediment depths within 2000 m of the earth’s surface. Second is the wide geographical distribution of the gas hydrates.

This report is a complete analysis of gas hydrates. The report explores the importance of
gas hydrates, their structure, where they are found, the rock physics model, and much more. Case studies of the Alaskan North Slope, Prudhoe Bay, and the Messoyakha Gas Field are all included in the report.






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Pages: 47
Publication Date: April 2008
Publisher: Energy Business Reports