After decades of research and multiple onshore arctic production experiments, Japan has taken a leap forward in natural gas production by conducting the first successful production test of natural gas from marine hydrates.
“This is the world’s first trial production of gas from oceanic methane hydrates, and I hope we will be able to confirm stable gas production,” announced Japanese Trade Minister Toshimitsu Motegi following ignition of the burner on the Japanese drilling ship Chikyu on March 12, 2013.
Provisional data from the Japan Oil, Gas and Metals National Corporation (JOGMEC) indicate that during the six-day production test, the well produced 120,000 cubic meters of natural gas with an average daily production of 20,000 cubic meters.
A 2008 onshore, five-and-a-half day test in Canada using similar methods produced a total of 13,000 cubic meters of natural gas.
Further data analysis will indicate if gas production from the marine methane hydrate prospect in the Nankai Trough is commercially viable.
This methane hydrate deposit lies 300 meters below the seafloor in waters 500 meters deep, 80 kilometers off the Pacific Coast of central Japan.
The Nankai Trough may hold 1.1 trillion cubic meters of methane hydrates – enough to replace all of Japan’s liquid natural gas (LNG) imports for 11 years.
Japan’s National Institute of Advanced Industrial Science and Technology estimates that over seven trillion cubic meters of methane hydrates, or a 100-year supply, resides in the marine sediment around Japan.
Japan plans to initiate a three-year study of its territorial waters in the Sea of Japan to measure marine methane hydrate reserves.
Utilizing depressurization, JOGMEC aims for technologically and economically viable production of methane hydrates within five years.
In a country dependent on LNG imports and facing an unsure future for its once prominent nuclear program, domestic gas production from hydrates offers the potential for Japan to “finally have an energy source to call its own,” said JOGMEC spokesman Takami Kawamoto.
A Methane Cage
Methane hydrates, or clathrates, are methane (C) molecules surrounded by solid water-ice lattices. The water molecules form a cage around, rather than bonding with, the methane.
Methane forms from biological and thermogenic processes. Biological methane is generated by the bacterial breakdown of organic material in shallow sediments.
Thermogenic methane is created when deeply buried organic-rich sediments are subjected to high temperatures and pressures. Such methane can move vertically through overlying sediment.
Methane hydrates form when methane gas reaches a depth and temperature where hydrates are stable and the gas becomes locked into the crystalline ice structure.
Methane hydrates are stable at high pressures and low temperatures. Arctic deposits predominantly occur in the lower parts of and beneath permafrost at depths greater than 200 meters. Marine deposits are found on and beneath the seafloor in water generally deeper than 500 meters. Gas hydrates have been identified in mounds on the seafloor, in veins and in cements in subsea sediments.
Production technology seeks to alter the surrounding conditions through heating or depressurization to achieve dissociation of the gas from the lattice structure. If ignited while dissociating, the methane hydrates look like “burning ice.”
The concentration of methane gas in hydrate deposits is significant: one cubic foot of hydrate contains 164 cubic feet of gas at surface temperature and pressure, according to the Department of Energy’s (DOE) National Energy Technology Laboratory (NETL).
Hydrate’s History
Once believed to exist only as synthetic products in the laboratory, naturally forming hydrates were discovered in the 1960s. Subsequent discoveries in the 1970s and 1980s of deposits in cores from the North Slope of Alaska and the Deep Sea Drilling Program prompted the creation of a national hydrate research and development (R&D) program in the United States in 1982.
Research in the 1980s and early 1990s focused on arctic permafrost deposits. Study of marine deposits began in 1995 with the Ocean Drilling Program’s Blake Ridge exploration offshore South Carolina.
While Blake Ridge methane hydrate concentrations are too low to allow commercial extraction, field testing in Japan’s Nankai Trough in 1998 and 1999 confirmed substantial natural gas reserves. Sandstone in the Nankai Trough was found to contain up to 80 percent methane hydrate saturation.
In the United States, the Methane Hydrate Research and Development Act of 2000 and its subsequent extension under the Energy Policy Act of 2005 established an interagency collaborative methane hydrate R&D program directed by the DOE.
Japan and Canada partnered to conduct production experiments in the 2000s in the Canadian Arctic, demonstrating the feasibility of producing natural gas from hydrates. In 2012, the United States and Japan, in partnership with ConocoPhillips, successfully produced methane gas from methane hydrates in the North Slope of Alaska.
Additional methane hydrate explorations have been conducted by other countries, including China, India and South Korea.
The NETL methane hydrates primer provides a more extensive history of gas hydrate R&D.
An Abundant Resource
Natural gas accounted for 24 percent of U.S. energy production in 2010 and is projected to increase to 30 percent by 2040, according to the U.S. Energy Information Administration’s Annual Energy Outlook 2013 Early Release.
Natural gas offers a fuel source that burns cleaner than other fossil fuels and may serve as a “bridge” fuel to aid in the transition to more renewable energy.
Methane hydrates represent a potentially vast resource that could create that “bridge.”
Estimates of total methane trapped in hydrates globally vary widely:
♦ Some estimates indicate that twice as much carbon exists in methane hydrates than in all other fossil fuels.
♦ The U.S. Geological Survey’s Gas Hydrates Project estimates global methane in hydrate form at between 100,000 trillion cubic feet (Tcf) — over 4,000 times the 2010 U.S. consumption — and 5,000,000 Tcf.
♦ NETL lists 700,000 Tcf as a common global methane estimate, but notes a possible range of 100,000 to 1,000,000 Tcf.
♦ Not all methane is technically or economically recoverable. Early estimates place technically recoverable methane at around 30,000 Tcf, according to the 2011 paper in Energy and Environmental Science by Boswell and Collett.
♦ The U.S. Bureau of Ocean Energy Management estimates that methane contained in the Gulf of Mexico would more than triple the U.S. total natural gas resource.
Natural gas in methane hydrate deposits may be a significant energy resource for the future. Research continues into the potential environmental and climatic impacts of methane extraction from hydrates.
Marine methane hydrate resources contain an order or two in magnitude more methane hydrate than permafrost resources, but have posed greater production challenges. Japan’s successful production is a tremendous technological breakthrough and offers hope of more easily accessing the world’s extensive marine hydrate resources.