A methane hydrate is a cage-like lattice of ice, inside of which are trapped molecules of methane (the chief constituent of natural gas). In fact, the name for its parent class of compounds, "clathrates," comes from the Latin word meaning "to enclose with bars."
Methane hydrates form in generally two types of geologic settings: (1) on land in permafrost regions where cold temperatures persist in shallow sediments, and (2) beneath the ocean floor at water depths greater than about 500 meters where high pressures dominate. The hydrate deposits themselves may be several hundred meters thick.
Scientists have known about methane hydrates for a century or more. French scientists studied hydrates in 1890. In the 1930s, as natural gas pipelines were extended into colder climates, engineers discovered that hydrates, rather than ice, would form in the lines, often plugging the flow of gas.
These crystals, although unmistakably a combination of both water and natural gas, would often form at temperatures well above the freezing point of ordinary ice. Yet, for the next three decades, methane hydrates were considered only a nuisance, or at best, a laboratory oddity.
That viewpoint changed in 1964. In a northern Siberian gas field named Messoyakha, a Russian drilling crew discovered natural gas in the "frozen state," or in other words, methane hydrates occurring naturally.
Subsequent reports of potentially vast deposits of "solid" natural gas in the former Soviet Union intensified interest and sent geologists worldwide on a search for how -- and where else -- methane hydrates might occur in nature. In the 1970s, hydrates were found in ocean sediments.
In late 1981, the drilling vessel Glomar Challenger, assigned by the National Science Foundation to explore off the coast of Guatemala, unexpectedly bored into a methane hydrate deposit. Unlike previous drilling operations which had encountered evidence of hydrates, researchers onboard the Challenger were able to recover a sample intact.
Today, methane hydrates have been detected around most continental margins. Around the United States, large deposits have been identified and studied in Alaska, the west coast from California to Washington, the east coast, including the Blake Ridge offshore of the Carolinas, and in the Gulf of Mexico.
In 1995, the U.S. Geological Survey (USGS) completed its most detailed assessment of U.S. gas hydrate resources. The USGS study estimated the in-place gas resource within the gas hydrates of the United States to range from 112,000 trillion cubic feet to 676,000 trillion cubic feet, with a mean value of 320,000 trillion cubic feet of gas.
Subsequent refinements of the data in 1997 using information from the Ocean Drilling Program have suggested that the mean should be adjusted slightly downward, to around 200,000 trillion cubic feet -- still larger by several orders of magnitude than previously thought and dwarfing the estimated 1,400 trillion cubic feet of conventional recovered gas resources and reserves in the United States.
Worldwide, estimates of the natural gas potential of methane hydrates approach 400 million trillion cubic feet -- a staggering figure compared to the 5,000 trillion cubic feet that make up the world's currently known gas reserves.
This huge potential, alone, warrants a new look at advanced technologies that might one day reliably and cost-effectively detect and produce natural gas from methane hydrates.
Why the new interest?
If only 1 percent of the methane hydrate resource could be made technically and economically recoverable, the United States could more than double its domestic natural gas resource base.
The United States will consume increasing volumes of natural gas well into the 21st century. U.S. gas consumption is expected to increase from almost 23 trillion cubic feet in 1996 to more than 32 trillion cubic feet in 2020 -- a projected increase of 40 percent.
Natural gas is expected to take on a greater role in power generation, largely because of increasing pressure for clean fuels and the relatively low capital costs of building new natural gas-fired power equipment.
Also, gas demand is expected to grow because of its expanded use as a transportation fuel and potentially, in the longer-term, as a source of alternative liquid fuels (gas-to-liquids conversion) and hydrogen for fuel cells.
Should the nation move to reduce carbon dioxide emissions, as part of our commitment to greenhouse gas reduction, the use natural gas potentially could increase even more.
Given the growing demand for natural gas, the development of new, cost-effective supplies can play a major role in moderating price increases and assuring consumer confidence in the long-term availability of reliable, affordable fuel.
Yet, today, the potential to extract commercially-relevant quantities of natural gas from hydrates is speculative at best.
With no immediate economic payoff, the private sector is not vigorously pursuing research that could make methane hydrates technically and economically viable.
Therefore, federal R&D is the primary way the United States can begin exploring the future viability of a high-risk resource whose long-range possibilities might one day dramatically change the world's energy portfolio.
Source: United States Energy Information Administration
© 2000 Mena Report (www.menareport.com)