Set a lighter to an icy block of methane hydrate, a naturally frozen combo of methane gas and water, and flames spew forth at random.
However unlikely this fluke of nature may appear — burning ice — it could hold the keys to a vast wealth of untapped, clean-burning methane gas thought to exist deep beneath the outer margins of most continental shelves.
Its contribution may be peripheral to the immediate needs of Western Europe and North America, currently drowning in cheap natural gas, but it present a potential lifeline to resource-poor nations like Japan, which already imports more than 90 percent of its fossil fuels.
Although successfully created in the laboratory as early as the 1800s, gas hydrates were only discovered in nature in western Siberian permafrost in the late 1960s. And their structural vagaries, capable of trapping this frozen methane in molecular, lattice cages, are only now being fully appreciated under natural conditions. It is known, however, that these methane hydrates typically form only at low temperatures and under high pressure in rock sediments, usually hundreds of feet or more below the ocean surface.
Such hydrates garnered some notoriety in 2010, when their presence stymied efforts to seal the blown Macondo well during the Gulf oil spill.
“The BP Deepwater Horizon Macondo well blew out 13,000 feet down,” said Arthur Johnson, a consulting geologist and chief of exploration at Hydrate Energy International in Kenner, Louisiana. “Hydrates didn’t cause the blow-out, but they complicated sealing the leak.” Hydrates have long been known to get in the way of drilling for undersea oil and natural gas, either by creating pipeline blockages and hazards while still frozen, or when heat from drilling releases their methane in its more volatile gaseous state.
Despite the news flap during the Deepwater Horizon disaster, hydrates’ potential as an alternative energy source remains mostly unappreciated. That’s partly with reason — to date, no one in the world can claim sustained gas hydrate energy production.
“The Japanese have by far led the world in their overall investment in looking at hydrates as a domestic energy resource,” said Tim Collett, a research geologist with the U.S. Geological Survey in Denver. “In 1995, the Japanese started the first hydrate research programs focused purely on energy potential.”
Recent events have goosed that interest. “After [last year’s] tsunami and earthquake damage to the Fukushima nuclear plant, the Japanese are actively working to phase out a lot of nuclear and go to natural gas,” Johnson explained. “The natural gas price there has jumped to $15 to $17 dollars per thousand standard cubic feet, so that’s an impetus to develop their own gas hydrate to generate electricity.”
To that end, the state-sponsored Japan Oil, Gas and Metals National Corporation has begun exploratory drilling in the Nankai Trough off Japan’s southeast coast. Koji Yamamoto, a corporation project director, says they will continue drilling four deep water holes until the end of March in preparation for a flow test early next year.
Conventional gas recovery from hydrates usually involves heating these with steam or hot water, or decreasing reservoir pressure enough to destabilize the hydrates into extractable gas and water.
But Japan Oil is also involved with the U.S. Department of Energy and Conoco-Phillips in testing a new method of producing methane hydrate energy on Alaska’s North Slope.
Conoco-Phillips is leading an effort to pump carbon dioxide into a 2,400-foot well in the western Prudhoe Bay oil field in order to learn how to extract a portion of the estimated 85 trillion cubic feet of methane gas thought to be buried under permafrost in the area.
“This is a very small-scale, controlled scientific experiment,” said geologist Ray Boswell, technology manager for gas hydrates with the Department of Energy in Morgantown, West Virginia. “We have been able to inject carbon dioxide into a reservoir that’s 85 percent [methane] hydrate, then we will start dropping the pressure in a controlled fashion and wait to see what flows into the well to better understand these chemical processes.”
What is known, said Johnson, is that “if you pump CO2 into a methane hydrate reservoir, the CO2 will displace the methane hydrate by forming a CO2 hydrate and releasing the methane.”
Some 22 tons of liquid CO2 were trucked in for the tests, which will continue through April. However, if this particular extraction mechanism were being done on a commercial scale, the needed CO2 might be collected from a nearby power plant, for instance.
Meanwhile, for the last decade, Chevron has been heading a project in the Gulf of Mexico with the U.S. Department of Energy. In 2009, the project team drilled seven exploratory wells at three different locations some 200 miles offshore. Boswell said that expedition determined that gas hydrates did accumulate at high saturations in sand reservoirs within the marine environment.
As Johnson points out, any country with a deepwater coastline has hydrate potential.
“But in the U.S., with $100 a barrel oil prices, natural gas ought to be about $17 per thousand standard cubic feet,” he said. Instead, it’s about $2.50 per right now.
For gas hydrates to be economically viable in the U.S., Johnson estimates that they would need a wholesale price of at least $9 per thousand standard cubic feet. That’s not likely anytime soon. The world currently uses about 117 trillion cubic feet of natural gas annually; U.S. consumption is a little over a quarter of that total.
Unless the current shale natural gas market completely collapses, in the short run, extracting gas hydrate is unlikely to be economically feasible in North America. But it offers advantages that make it worth developing.
“Relative to coal, methane gas produces only half the CO2 and no mercury, particulates, or ash,” said Johnson. “You might even be able to take CO2 produced from an [industrial] plant and sequester that CO2 for thousands of years, [with potential] tax credits for doing so.”
Couple its clean-burning potential with the fact that it’s so ubiquitous, and it’s arguably enough to give gas hydrate energy a hard second look. Some estimates put the global amount of gas hydrates at as much as 43,000 trillion cubic feet in sandstone reservoirs alone. Even if only half of that is recoverable, Johnson says that they could still represent a significant global energy reserve for well over a century.