Issued on: September 23, 2002
Ocean Research Vessel Returns with Undersea 'Treasure' of Hydrates
Largest Amount of Marine Hydrate Core Ever Recovered
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The R/V JOIDES Resolution |
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).
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| Cross sections of methane hydrate core samples |
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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 Ridge expedition.
"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.
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| Anne Tréhu (Co-Chief Scientist; USA) and Brad Julson (Laboratory Officer) discuss one of the first sediment cores recovered during Leg 204. |
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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.
The 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.
-End of Techline-
Program Office Contact:
William Gwilliam, Strategic Center for Natural Gas, DOE National Energy Technology Laboratory, (304) 285-4401 e-mail: wgwill@netl.doe.gov
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