The National Methane Hydrates R&D Program
All About Hydrates - Occurences of Natural Methane Hydrate
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Methane Hydrates Worldwide |
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Up until the 1960s, methane hydrate was considered
an unusual and unnatural substance that occurred only in chemical
laboratories and natural gas pipelines. No one suspected that it could exist
in sizeable quantities in nature. However, a string of discoveries, first in
Polar Regions and then spreading throughout the deep-water shelves of every
continent, has revealed that natural methane hydrate occurs on a truly
staggering scale.
In many areas, the existence of natural methane hydrate is inferred
only from indirect evidence obtained through geophysical surveys or
geochemical analyses of sediment samples. However, there are a growing
number of localities where detailed information is being collected. Each
of these localities, with their own unique geologic settings, is
unveiling surprising information that questions the initial theories of
hydrate formation and ultimately advances the general state of knowledge
of natural gas hydrate.
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Arctic Region surrounding Mallik
well site |
A prime locality for the study of natural methane hydrate is within the
Arctic Regions of North America. Although hydrates associated with
permafrost contain only a small fraction of the global methane hydrate
resource, areas like the North Slope of Alaska provide excellent
opportunities to study natural hydrates by combining the data gained
from more than two decades of well drilling with relative ease of
access. In 1998, the Mackenzie River Delta of Canada's Northwest
Territories was the site of the world's first research well drilled
specifically to study natural methane hydrate. The Messoyahka gas field
of the West Siberia basin is another well-known example of an arctic
hydrate accumulation. Hydrate was inferred from well logging and other
data during initial drilling of the field in 1964, and debate continues
as to whether dissociation of the hydrate in response to production of
deeper free gas zones has resulted in actual production of methane from
hydrate.
Perhaps the best-known and most closely studied oceanic hydrate
locality is the Blake Ridge, a large pile of deep-water sediment located
off the eastern coast of North America. The Blake Ridge has been scanned
and probed regularly since the first evidence of hydrate was collected
there in the early 1970s. The Blake Ridge's uniform sediment makes it an
ideal laboratory for fine tuning the tools and techniques that will be
used to study hydrate accumulations around the globe.
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Hydrate mound on sea floor |
A third prominent locality for hydrate occurrence is the deep-water
Gulf of Mexico. Unlike the Atlantic shore, the Gulf is an area of
significant production of conventional oil and gas. The hazards that
unintentional hydrate dissociation pose for drill rigs, pipelines, and
other equipment is a prime driver for focused study of hydrates in the
Gulf. The significant geologic differences that exist between the Blake
Ridge and the Gulf result in the presence of unique features, including
visible mounds of hydrate directly on the sea floor. In recent years,
scientists have visited the deep gulf in submersible vehicles to observe
and sample the mounds. Among the many discoveries are unique
chemosynthetic communities, including previously unknown species called
ice worms, that derive sustenance not from the sun, but directly from
the methane slowly dissociating from the hydrate.
In 1999, Japan's Nankai trough region was the target of the first well
drilled specifically to test the resource potential of oceanic hydrate.
A second, more extensive, round of drilling was conducted in 2003. The geologic setting (a subduction zone), characterized by the close
proximity of deep water to the land and the resultant improved reservoir
character of the sediment, may eventually result in the Nankai region
being the host to the first attempts at commercial methane production
from hydrate. Examination of a similar tectonic setting on the Pacific
coast of North America has resulted in identification of a promising
hydrate locality named "Hydrate Ridge", located offshore Oregon. Hydrate
Ridge was the subject of scientific drilling by the International
Ocean drilling Project (IODP) in 2002 (Leg 204). A new round of IODP drilling will occur in 2005 at a site further north, offshore Vancouver Island.
Many other regions have also been appraised to various extents,
including offshore Alaska, Antarctica, Nigeria, the South China Sea,
Norway, Peru, and Australia. As information becomes available on these
areas, we will post specific pages for each new site.
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