Even with current natural gas supplies well outpacing demand in the United States, the fact that the natural resource is in finite supply means the quest for new sources -- such as natural gas from gas hydrates -- continues. Gas hydrates, a frozen form of natural gas that bursts into flames at the touch of a match, is showing increasing promise as an abundant, untapped source of clean, sustainable energy, according to the U.S. Geological Survey (USGS).
The USGS said natural gas derived from chunks of ice that workers collect from beneath the ocean floor and beneath the arctic permafrost may fuel cars, heat homes and power factories. The icy chunks could supplement traditional energy sources that are in short supply and which produce large amounts of carbon dioxide linked to global warming, U.S. government scientists say.
"These gas hydrates could serve as a bridge to our energy future until cleaner fuel sources, such as hydrogen and solar energy, are more fully realized," says study co-leader Tim Collett, a research geologist with the USGS in Denver. Collett said gas hydrates -- known as "ice that burns" -- hold special promise for helping to combat global warming by leaving a smaller carbon dioxide footprint than other fossil fuels.
Recently a group of researchers in New York said it has discovered an optimal temperature and pressure range for maximizing production of natural gas from the icy hydrate material. Marco Castaldi, Yue Zhou and Tuncel Yegualp, of the Department Earth and Environmental Engineering at the Henry Krumb School of Mines of Columbia University, built what they believe to be the world's largest experimental reactor, filled with sand, water and methane, to simulate the formation of gas hydrates (at low temperatures and high pressure) and production of the gas. While depressurizing the hydrates to free the methane, the researchers observed a boost in natural gas production between a narrow range of temperatures and pressures. Castaldi, Zhou and Yegualp concluded that maintaining gas production at the settings they observed could be a key step in boosting production of methane on an industrial scale.
Last November a team of USGS researchers that included Collett announced a giant step toward that bridge to the future (see NGI, Nov. 17, 2008). The USGS scientists in a study estimated that 85.4 Tcf of natural gas could potentially be extracted from gas hydrates in Alaska's North Slope region, enough to heat more than 100 million average homes for more than a decade.
"It's definitely a vast storehouse of energy," Collett said. "But it is still unknown how much of this volume can actually be produced on an industrial scale." He says the volume depends on the ability of scientists to extract useful methane, the main ingredient in natural gas, from gas hydrate formations in an efficient and cost-effective manner. Scientists worldwide are doing research on gas hydrates in order to understand how this strange material forms and how it might be used to supplement coal, oil and traditional natural gas, the USGS said.
While gas hydrates were discovered decades ago, scientists have only recently begun to try to use them as an alternative energy source. Gas hydrates, also known as clathrates, form when methane gas from the decomposition of organic material comes into contact with water at low temperatures and high pressures. Those cold, high-pressure conditions exist deep below the oceans and underground on land in certain parts of the world, including the ocean floor and permafrost areas of the Arctic.
According to the USGS, researchers are finding tremendous stores of gas hydrates throughout the world, including the United States, India and Japan. In addition to Alaska, the United States has vast gas hydrate deposits in the Gulf of Mexico and off its eastern coast. Interest in and support of hydrate research is now growing worldwide. The USGS said Japan and India currently have among the largest, most well funded hydrate research programs in the world.
"Once we have learned better how to find the most promising gas hydrate deposits, we will need to know how to produce it in a safe and commercially viable way," says study co-author Ray Boswell, who manages the National Methane Hydrate R&D Program of the U.S. Department of Energy's National Energy Technology Laboratory in Morgantown, WV. "Chemistry will be a big part of understanding just how the hydrates will respond to various production methods."
One of the more promising techniques for extracting methane from hydrates involves simply depressurizing the deposits, Boswell said, while another method involves exchanging the methane molecules in the clathrate structure with carbon dioxide. In theory, producers can collect the gas using the same drilling technology used for conventional oil and gas drilling, he said.
"Gas hydrates are totally doable," Collett added. "But when and where we will see them depends on need, motivation and our supply of other energy resources. In the next five to 10 years, the research potential of gas hydrates will be more fully realized."
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