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by Carolyn Ruppel, Jessica Robertson, and Brenda Pierce

As widely reported in the news media, Japan produced methane from deepwater gas hydrate deposits for the first time in March 2013. This crucial milestone along the research-and-development pathway toward proving that gas hydrates may eventually be an energy resource was achieved by Japan's Research Consortium for Methane Hydrate Resources (known as MH21). Two months earlier, in January 2013, U.S. Geological Survey (USGS) Gas Hydrates Project personnel from the Woods Hole Coastal and Marine Science Center in Woods Hole, Massachusetts, collaborated with researchers from the Georgia Institute of Technology (Georgia Tech); the Japan Oil, Gas and Metals National Corporation (JOGMEC); and Japan's National Institute of Advanced Industrial Science and Technology (AIST) to analyze special sediment cores retrieved from the area of the deepwater production test. The collaboration continues a long-standing relationship between national methane hydrates research programs in Japan and the United States, and it represents the first time that U.S. researchers have been directly involved in studying Japanese gas hydrate samples.

What are Gas Hydrates?

Gas hydrates are a naturally occurring, ice-like 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.

Gas hydrates form when methane—and sometimes other gases—combines with water at specific pressure and temperature conditions. These pressure-temperature conditions keep the gas hydrate "stable," meaning it is intact and gases are contained in a solid form. Gas hydrates are widespread in marine sediments beneath the ocean floor and in sediments within and beneath permafrost.

Premier Research in Japan Enhances Understanding in the United States

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In 2012, JOGMEC and AIST researchers used innovative technology to retrieve and preserve sediment samples containing gas hydrate from the seafloor in the Nankai Trough area, offshore Japan. Such well-preserved hydrate-bearing sediment samples are rare. They are preserved as "pressure cores," with the gas hydrates maintained at the pressure at which they formed beneath the seafloor. Maintaining these pressure conditions and storing the recovered cores at low temperatures in walk-in freezers ensure that the gas hydrate in the cores remains intact. Researchers have been refining pressure-core technology since the 1990s, and the version of the pressure corer used in the Nankai Trough was designed specifically to retrieve coarse-grained (for example, sandy) hydrate-bearing sediments, where the highest saturations of gas hydrate are likely to occur. The pressure corer used offshore Japan was developed as part of an ongoing collaboration among Japan, the U.S. Department of Energy (DOE), and the Gulf of Mexico Gas Hydrate Joint Industry Program (JIP).

Innovative Technology to Study the Samples

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During January's joint laboratory program in Sapporo, Japan, U.S. and Japanese researchers analyzed the pressure cores using specialized devices that keep the cores at their natural, stable conditions. The devices, called Pressure Core Characterization Tools (PCCT), were designed and built by geotechnical engineer Carlos Santamarina at Georgia Tech, with long-term support from DOE and JIP. Examples of PCCT devices are a manipulator for moving pressure cores from storage chambers into various testing chambers, special pressure vessels that measure the strength of the sediments and how quickly fluids can flow through them, and a biological chamber that can be used to study the microbes that live in the deep-sea sediments.

A key tool in the suite of PCCT instruments is the Instrumented Pressure Testing Chamber (IPTC), which was the first device capable of measuring certain properties of pressure cores without first depressurizing them. The IPTC was built by Georgia Tech in 2005 and has previously been deployed by Santamarina and his graduate students to analyze pressure cores obtained from the Gulf of Mexico, offshore India, and the Ulleung Basin offshore Korea. USGS researchers, led by engineer Bill Winters and Gas Hydrates Project laboratory chief Bill Waite, now operate, maintain, and spearhead improvements to the IPTC, with technical assistance from USGS technicians Dave Mason and Emile Bergeron.

Testing the PCCT instruments in Japan was an important step in preparing USGS and Georgia Tech researchers for the analysis of pressure cores that may be obtained in the future from gas hydrate deposits in the deepwater Gulf of Mexico and on the Alaskan North Slope. Along with offshore 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

The IPTC is also capable of conducting mini-production tests on hydrate-bearing sediments. During these tests, cores are depressurized at closely controlled rates to break down 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 gas hydrate reservoirs. Georgia Tech has previously completed such tests on pressure cores from offshore India and Korea.

As part of the program in Japan, AIST manufactured an IPTC for completion of laboratory production tests on the Nankai Trough pressure cores. Coupling the results of mini-production tests with those from field-scale tests done in March 2013 will yield new insights that may lead to the realization of gas hydrates as an energy resource.

Financial Support

This collaborative research in Japan was financially supported by MH21, the USGS, DOE, and JIP.

USGS Gas Hydrates Project

The USGS Gas Hydrates Project is a globally recognized research effort that focuses on energy, climate, and geohazard issues associated with natural-gas hydrates. Research locations include the northern Gulf of Mexico, the Alaskan North Slope, the Arctic Ocean, the Bering Sea, and the U.S. Atlantic Ocean margin, as well as Japan, India, and Korea.