Methane hydrate is sometimes called “the ice that burns” because the warming hydrates release enough methane to sustain a flame. Photo Credit: USGS

A new project in Japan is helping scientists make significant progress in studying gas hydrates as a potential source for natural gas production. This research advances understanding of the global distribution of gas hydrates as well as whether and how methane contained in gas hydrates can be used as a viable energy source.

The collaboration continues a long-standing relationship between national methane hydrates research programs in Japan and the U.S., but represents the first time that U.S. researchers have been directly involved in studying Japanese gas hydrate samples. In the current phase of this project, an international group of scientists from Japan, the U.S. Geological Survey (USGS), and Georgia Institute of Technology (Georgia Tech) are employing cutting-edge technology and studying rare gas hydrate samples recovered deep beneath the seafloor.

What are Gas Hydrates?

Gas hydrates are a naturally occurring, solid form of methane gas combined with water. They sequester large amounts of methane, making them a potentially significant source for natural gas around the world.

To give more detail, gas hydrates are an ice-like substance formed when methane—and sometimes other gases—combine with water at specific pressure and temperature conditions. Gas hydrates are widespread in marine sediments beneath the ocean floor and in sediments within and beneath permafrost areas. These pressure-temperature conditions keep the gas hydrate “stable,” meaning it is intact and gasses are contained in its solid form.

Premier Research in Japan Enhances Understanding in the U.S.

A multiyear, premier research program in deepwater gas hydrate exploration and production is currently underway in Japan. Last year, Japanese researchers used innovative technology to retrieve and preserve sediment samples containing gas hydrates. These samples were obtained from layers beneath the deep seafloor in the Nankai Trough offshore Japan.

Such well-preserved samples are extremely rare. They are preserved as “pressure cores,” with the gas hydrates kept as if they were still at the natural conditions in the subsurface where they formed. Gas hydrates are only stable at certain pressures and temperatures, and scientists have been working since the 1990s on sophisticated techniques to retrieve and preserve samples.

The program is being led by the Japan Oil, Gas and Metals National Corporation (JOGMEC) and Japan’s National Institute of Advanced Industrial Science and Technology (AIST). The project is being conducted in collaboration with the USGS Gas Hydrates Project and researchers from the School of Civil and Environmental Engineering at Georgia Tech. This project is one component of an ongoing Japanese collaboration on methane hydrate research with the U.S. Department of Energy (DOE) and the Gulf of Mexico Gas Hydrate Joint Industry Project (JIP).

Photograph of the international team studying gas hydrates in Japan. Front row, kneeling: Jun Yoneda (AIST). Front row, standing, left to right: Yoshihiro Konno (AIST), Jiro Nagao (AIST), Marco Terzariol (Georgia Tech), William Winters (USGS), Junbong Jang (Georgia Tech), Kiyofumi Suzuki (JOGMEC), Sheng Dai (Georgia Tech), Tetsuya Fujii (JOGMEC), and Emile Bergeron (USGS). Back row, standing, left to right: William Waite (USGS), Efthymios Papadopoulos (Georgia Tech), David Mason (USGS), and Carlos Santamarina (Georgia Tech). Photo Credit: USGS

Innovative Technology to Study the Samples

U.S. and Japanese researchers are now analyzing the cores using specialized devices that keep the cores at their natural, stable conditions.

The devices are called Pressure Core Characterization Tools (PCCT), which were designed and built by Georgia Tech with long-term support from the DOE and JIP. Scientists from Georgia Tech and the USGS will be operating these devices.

The key tool is the Instrumented Pressure Testing Chamber, which was the first device capable of measuring certain properties of pressure cores without first depressurizing them. An example of another device is special pressure vessels that measure the strength of the sediments and how quickly fluids can flow through the sediments.

Testing these instruments in Japan will also help prepare for the analysis of pressure cores that may be obtained in the future from hydrate deposits in the deepwater Gulf of Mexico and on the Alaskan North Slope. Along with Japan, these areas are ideal locations for future research to assess the occurrence and production potential of gas hydrates.

USGS Weighs In

“This research will not only help us understand the character of gas hydrates in Japan, but we can also apply that knowledge as well as this innovative technology and approach to understand the potential in the U.S. and around the world,” said Brenda Pierce, USGS Energy Resources Program Coordinator. “This project brings together international experts, each with specialized knowledge to share about these important hydrate deposits. The USGS is excited that our Japanese colleagues have invited us to participate in this project along with Georgia Tech.”

Mini-Production Tests and Future Publications

Japanese researchers are also conducting the first offshore production test to track how much methane can be released from deepwater gas hydrate deposits. Focus will be in the Nankai Trough, which is where the cores being studied now were recovered.

Japan’s AIST has manufactured an instrument that will be used to conduct laboratory production tests on the pressure cores. During these tests, the cores will be depressurized at closely controlled rates to breakdown the methane hydrate and release natural gas. By measuring the volume of gas produced and the rate of production, insight may be gained regarding the potential behavior of the reservoirs during the planned field test. Mini-production tests and future full-scale field production tests are a required step to potentially realize gas hydrates as an energy resource.

Official publications from this project are scheduled for two years from now.

Gas hydrate recovered in shallow layers just below the seafloor during piston coring in the Gulf of Mexico. Photo Credit: USGS

Financial Support

This collaborative research in Japan was financially supported by MH21, USGS, DOE, and the multinational Gulf of Mexico Gas Hydrates JIP.

USGS Gas Hydrates Project

The USGS has a globally recognized research effort studying gas hydrates in many different settings around world. Research locations include Japan as well as the U.S. Beaufort Sea, Alaska’s North Slope, India, Korea and the northern Gulf of Mexico.

In addition to energy, climate studies are another focus of USGS gas hydrates research. There are concerns that as the climate warms, gas hydrates may break down and release large volumes of methane into the atmosphere, which would further exacerbate climate warming. USGS scientists are studying this interaction, particularly in the Arctic. Research has indicated that most of the world’s gas hydrate deposits should remain stable for the next few thousand years. Of the gas hydrates likely to become unstable, few are likely to release methane that could reach the atmosphere and intensify climate warming.

Photographs

Photographs of the international research team conducting analysis in Japan are available at: http://gallery.usgs.gov/tags/GasHydrates

Contacts

Jessica Robertson

Public Affairs, U.S. Geological Survey

Phone: 703-648-6624

Email: jrobertson@usgs.gov

Carolyn Ruppel

Gas Hydrates Project Chief, U.S. Geological Survey

Phone: 617-806-6768

Email: cruppel@usgs.gov

Liz Klipp

Media Relations, Georgia Institute of Technology

Phone: 404-894-6016

Email: klipp@gatech.edu

Group of Administrative Coordination
Research Consortium for Methane Hydrate Resources in Japan (MH21)

Email: mh21info@jogmec.go.jp

But recent research indicates that most of the world’s gas hydrate deposits should remain stable for the next few thousand years. Of the hydrates likely to become unstable, few are likely to release methane that could reach the atmosphere and intensify global warming.

Figure 1: Gas hydrates have been found in many locations worldwide. Scientists predict that they occur in many areas that have not yet been surveyed.

Background: Gas hydrates are an ice-like combination of natural gas and water that can form in deep-water ocean sediments near the continents, and within or beneath continuous permafrost in the circum-Arctic. Specific temperatures and pressures and an ample supply of natural gas are required for gas hydrates to form and remain stable.

Figure 2: Solid gas hydrate recovered from sediments about 20 feet below the seafloor near Canada’s Vancouver Island

An estimated 99 percent of gas hydrates are in ocean sediments, with the remaining 1 percent in permafrost areas (fig.1). Methane hydrate or “methane ice” is the most common type of gas hydrate (fig. 2). It is a highly concentrated form of methane. One cubic foot of methane hydrate traps about 164 cubic feet of methane gas.

The amount of methane trapped in the earth’s hydrate deposits is uncertain, but even the most conservative estimates conclude that about 1000 times more methane is trapped in hydrates than is consumed annually worldwide. The most active area of gas hydrate research focuses on their potential as an alternate source of natural gas (fig. 3), and the USGS Gas Hydrates Projecthas several programs in this area.

Gas Hydrates and Climate Change– A Theoretical View

Figure 3: Methane hydrate is sometimes called “the ice that burns” because the warming hydrates release enough methane to sustain a flame.

Gas hydrate researchers are examining the link between climate change and the stability of methane hydrate deposits. A warming climate could cause gas hydrates to break down (dissociate), releasing the methane that they now trap.

Methane is a potent greenhouse gas. A given volume of methane causes 15 to 20 times more greenhouse gas warming than carbon dioxide, so the release of large quantities of methane to the atmosphere could exacerbate atmospheric warming and cause more gas hydrates to destabilize (fig. 4).

Figure 4: Schematic of the theoretical scenario -- Arctic methane emissions from gas hydrates and increased climate warming.

Some research suggests that this has happened in the past. Extreme warming during the Paleocene-Eocene Thermal Maximum about 55 million years ago may have been related to a large-scale release of global methane hydrates. Some scientists have also advanced the Clathrate Gun Hypothesis to explain observations that may be consistent with repeated, catastrophic dissociation of gas hydrates and triggering of submarine landslides during the Late Quaternary (400,000 to 10,000 years ago).

Methane in the Atmosphere: Current Observations

The atmospheric concentration of methane, like that of carbon dioxide, has increased since the onset of the Industrial Revolution (fig. 5). Methane in the atmosphere comes from many sources, including wetlands, rice cultivation, termites, cows and other ruminants, forest fires, and fossil fuel production (fig. 6). Some researchers have estimated that up to 2 percent of atmospheric methane may originate with dissociation of global gas hydrates. Currently, scientists do not have a tool to say with certainty how much, or if any, atmospheric methane comes from hydrates.

Although methane is a potent greenhouse gas, it does not remain in the atmosphere for long. Within about 10 years, it is transformed to carbon dioxide. Thus, methane that is released to the atmosphere ultimately adds to the amount of carbon dioxide, the main greenhouse gas.

Figure 5: Atmospheric concentrations of carbon dioxide in parts per million and methane in parts per billion. Source: NOAA

Figure 6: Possible sources of atmospheric methane. Currently, there is no proof that gas hydrates are contributing to total atmospheric methane budgets. Source: U.S. Department of Energy, Methane Hydrates R&D Program

Expected Impact of Warming Climate on Methane Hydrate Deposits For the most part, warming at rates documented by the Intergovernmental Panel on Climate Change for the 20th century should not lead to catastrophic breakdown of methane hydrates or major leakage of methane to the ocean-atmosphere system from gas hydrates that dissociate. While the vast majority of methane hydrates would require a sustained warming over thousands of years to trigger dissociation, gas hydrates in some locations are dissociating now in response to short-term and long-term climate processes.

The following discussion refers to the numbered type locales or sectors, shown in Figure 7.

Figure 7: Gas hydrate deposits by sector. Currently, gas hydrates are most likely dissociating in sectors 2 and 3. Only sector 2 is likely to release methane that could reach the atmosphere. Figure modified from Ruppel (2011).

Sector 1, Thick Onshore Permafrost: Gas hydrates that occur within or beneath thick terrestrial permafrost will remain largely stable even if climate warming lasts hundreds of years. Over thousands of years, warming could cause gas hydrates at the top of the stability zone, about 625 feet below the earth’s surface, to begin to dissociate.

Sector 2, Shallow Arctic Shelf: The shallow water continental shelves that circle parts of the Arctic Ocean were formed when sea level rise during the past 10,000 years inundated permafrost that was at the coastline. Subsea permafrost is thawing beneath these continental shelves and associated methane hydrates are likely dissociating now. If methane from these gas hydrates rises to the ocean floor, it will likely reach the atmosphere. Less than one percent of the world’s gas hydrates probably occur in this setting, but this estimate could be revised as scientists learn more.

Sector 3, Upper Edge of Stability: Gas hydrates on upper continental slopes, beneath 1000 to 1600 feet of water, lie at the shallowest water depth for which methane hydrates are stable. The upper continental slopes, which ring all of the world’s continents, could host gas hydrate in zones that are roughly 30 feet thick. Warming ocean waters could completely dissociate these gas hydrates in less than 100 years. Methane emitted at these water depths will probably oxidize in the water column or simply dissolve and is not likely to reach the atmosphere. About 3.5 percent of the earth’s gas hydrates occur in this climate sensitive setting.

Sector 4, Deepwater: Most of the earth’s gas hydrates, about 95 percent, occur in water depths greater than 3000 feet. They are likely to remain stable even with a sustained increase in bottom temperatures over thousands of years. Most of the gas hydrates in these settings occur deep within the sediments. If they do dissociate, the released methane should remain trapped in the sediments, migrate upward to form new gas hydrates, or be consumed by oxidation in near-seafloor sediments. Most methane released at the seafloor would likely dissolve or be oxidized in the water column. A recent article, Methane Hydrates and Contemporary Climate Change, provides more detail.

USGS Gas Hydrates Project

Figure 8: USGS researchers deploy a mini-sparker source to image seafloor sediments in the shallow Beaufort Sea near Prudhoe Bay, Alaska, August 2011. The USGS and the U.S. Department of Energy are cooperating in this work.

The USGS is studying various sources of methane and the impact of climate change. Since 2009, the USGS Gas Hydrates Project has been conducting field research to determine whether gas hydrates are currently dissociating due to climate warming and, if so, how much methane emitted from these gas hydrates might reach the atmosphere. Research locations include the U.S. Beaufort Sea and Alaska’s North Slope. The USGS has also organized workshops to identify priorities in climate-hydrates research and to plan ocean drilling projects related to these issues.

Contact: Diane Noserale