VICTORIA, BRITISH COLUMBIA - An internationally funded
ocean research vessel has returned to port after a two-month expedition
off the Oregon coast, bringing with it the largest amount of marine methane
hydrate core samples ever recovered for scientific study.
The R/V JOIDES Resolution, the world's largest scientific drillship,
docked at Victoria, British Columbia earlier this month and began offloading
pressure vessels containing methane hydrates recovered 50 miles offshore
of Oregon from an area known as Hydrate Ridge.
The pressure vessels, each six feet long and four inches in diameter,
will be shipped to Texas A&M University for study by scientists from
around the globe. Their detailed analyses of the icy substance could reveal
new clues about a strange natural occurrence that many believe could hold
the key to a virtually inexhaustible supply of natural gas.
Methane hydrates are ice crystals that encase natural gas. They form
when methane generated from organic rich sediments or migrating from deeper
gas deposits becomes entrapped in water frozen by the right combination
of pressure and low temperatures. Such conditions often occur on land
in permafrost regions or within ocean floor sediments at water depths
below 500 meters (or just over 1600 feet).
Methane hydrates look like dirty chunks of ice, but if touched by a flame,
the ice burns.
As late as 1981, no scientist had ever seen a methane hydrate sample
brought up intact from the ocean floor. Now substantial evidence exist
that hydrates abound along the seafloor and beneath the Arctic tundra.
Their energy potential could be staggering. The in-place gas estimates
for hydrates in and around the United States could amount to as much as
200,000 trillion cubic feet, dwarfing the country's estimated 1,400 trillion
cubic feet of conventional natural gas resources and reserves. But hydrates
also could pose a safety threat to offshore oil and gas platforms, and
sudden seafloor landslides could release methane, a powerful greenhouse
gas, into the atmosphere.
The U.S. Department of Energy, through its Fossil Energy research program,
has placed a high priority on learning more about the geologic occurrences
and composition of the world's hydrate formations. The agency contributed
more than $1 million and several pieces of research equipment to the Hydrate
"Methane hydrates are still very much a puzzle to scientists and
petroleum geologists, and the scientific community is still trying to
fit all the pieces together," said Bill Gwilliam, an Energy Department
project manager who was onboard the R/V JOIDES Resolution for part of
the expedition. "But now, as a result of this latest expedition,
we have a lot more ‘pieces' to study."
Known officially as Leg 204 of the Ocean Drilling Program (ODP), the
expedition was dedicated to investigating the origin and distribution
of gas hydrates around Hydrate Ridge, an area where two of the Earth's
major tectonic plates converge. Previous scientific surveys of the area
have revealed massive accumulations of hydrates.
Scientists from 11 nations – the United States, Germany, Japan,
Canada, Spain, Norway, the United Kingdom, Taiwan, the People's Republic
of China, and South Korea – participated in the expedition which
took place from July 6 to September 2, 2002.
Working onboard the floating laboratory, the scientists were able for
the first time to analyze gas hydrates brought to the surface without
releasing the subseafloor pressures that keep the methane gas trapped
inside the frozen crystals.
"This provided an unprecedented opportunity to study the physical
properties of gas hydrates in their natural state," said Gwilliam.
Researchers used special pressure coring tools – two recently developed
by a European consortium and one developed in the Ocean Drilling Program
– to extract the core samples while preserving the in-situ, or "in
place,"conditions. Part of the Energy Department's funding went to
upgrade the ODP Pressure Core Sampler used in this effort.
The Energy Department also provided the specially-designed pressure vessels
used to preserve core samples for further studies. Thirty-four of these
pressure vessels, containing their scientifically-valuable ice cores,
are now on their way to researchers.
Anne Tréhu (Co-Chief Scientist;
USA) and Brad Julson (Laboratory Officer) discuss one of the first
sediment cores recovered during Leg 204.
In all, more than 3,064 meters – nearly two miles – of core
were extracted from the ocean floor during the expedition, although not
all of it contained hydrates. To look for telltale density contrasts that
might indicate the presence of hydrates, scientists used an x-ray linear
scanner built just a month before the expedition began by the Energy Department's
Lawrence Berkeley National Laboratory.
Infrared thermal imaging cameras, a nuclear magnetic resonance logging-while-drilling
tool, and other instruments were used to investigate hydrate distributions
in place and within the ocean sediments recovered in the coring operations.
A key goal of the expedition was to physically verify the presence of
hydrates with core samples. These samples would then be compared with
a variety of conventional wireline logging and logging-while-drilling
data (that reveal the physical and chemical properties of cores) and seismic
data that allow correlation of ocean bottom layers. Such correlations
are crucial if petroleum geologists are to reliably locate commercially
productive deposits of hydrates in the future.
On Leg 204, for the first time, core samples were acquired simultaneously
with logging-while-drilling data to provide a direct comparison.
Ocean Drilling Program is an international partnership of scientists and
research institutions organized to study the evolution and structure of
the Earth. The program is funded primarily by the U.S. National Science
Foundation and its international partners. It is managed by the Joint
Oceanographic Institutions, a consortium of academic institutions. Texas
A&M University is responsible for science operations, and Lamont-Doherty
Earth Observatory of Columbia University was responsible for logging operations.