Since last years Hydrates updated, a survey on hydrates was carried out in the Gulf of Mexico (GOM). Seven deepwater slim holes were drilled last April as part of Leg II of the Joint Industry Project (JIP Leg II). The results were claimed by Dr Collett to be "very encouraging"
What are the hydrate in-place resource estimates?
In its 2000 report Oceanic gas hydrate research and activity review [pdf!] (MMS 2000-017), the MMS claimed (Kvenvolden 1993) that the distribution of worldwide organic carbon in gas hydrate (onshore and offshore = 10 000 Pg) was twice the amount of fossil fuels (coal, oil and natural gas = 5 000 Pg). This figure was still being used by the USGS in 2006 (Collett et al). This was unrealistic because most hydrates are located in the first 600 m of recent oceanic sediments (water depth > 500 m) which covers a period of time of a few millions years, while fossil fuels sediments cover a period of about one billion years, with larger surface and thickness (>6000 m).
In his book "The Deep, Hot Biosphere" Thomas Gold in July of 1992 (which convinced the Swedish government to drill two wells on the Siljan meteorite crater looking for abiogenic oil and gas. He justified his theory by the large volume of oceanic hydrates:
The large quantities of methane hydrates (methane-water ices) found in many areas of the ocean floor, and thought to contain more methane than all other known methane deposits, suggest a widely distributed methane supply from below.
Production
A Permafrost hydrate in sandy sediments is quite different from an oceanic hydrate in clay, mostly unconsolidated sediments. Permafrost hydrates were drilled in oil and gas producing basins: they are old accumulations and mainly thermogenic. Oceanic hydrates were drilled in oil and gas producing basins (e.g. GOM). In the North Slope hydrates seem quite uneconomical (the Mallik test was less than a CBM test) and their interest is negligible when Prudhoe Bay free gas reserves are still stranded (in unconventional production the size of the tank does not matter, it is the size of the tap!). It is a far future prospect, needing first a gas pipeline and much higher gas prices because of the small flow (no pressure because shallow depths). Collett et Petrotech 2009 (Geologic and engineering controls on the energy resource potential of gas hydrates [pdf!]) states that the maximum rate on Mallik 2008 was 4000 m3/d .There is no production concept for oceanic hydrates, because no one knows how to extract them, if they mainly lie in unconsolidated impermeable sediments. Furthermore, the heterogeneity of oceanic hydrates (few centimetres vertically and few meters horizontally) seems to be a difficult obstacle to overcome.
Conclusions
Hydrate is the Santa Claus of many who do not want to change their way of life. But hydrate occurrences are hard to evaluate, mainly because of a lack of samples (cores), which is the only way to calibrate all the visible proxies: well logs and seismic data.The GOM is now claimed to have the "most promising marine gas hydrate accumulations in the world", but unfortunately this is only wishful thinking without the coring, which is now planned only for 2011 or later. As usual, the data is incomplete to back up such optimistic claims, in particular for the GOM.
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