SECONDARY Article: Energy on Ice - Methane Hydrates
What are the energy sources of the future? Some scientists believe methane hydrate is one of the answers. But what, exactly, is it? A gas hydrate, such as methane hydrate, is a crystalline solid known as a clathrate. The word clathrate has its origins in the Latin word meaning “to enclose with bars.” It follows then that clathrates are a class of chemical substances made of two unique materials, one of which encloses the other in an open, lattice-like cage. There is no chemical bonding to hold the two materials together, only the physical structure. The most abundant naturally forming clathrate is methane hydrate.
Methane hydrate is formed when water molecules freeze around a molecule of methane gas. It is typically found in two distinct geologic areas—on land in the subsurface sediments of permafrost regions, or in oceanic sediments under at least 450 meters of water. Pressure, temperature, and the availability of water and methane are the determining factors in how much hydrate develops. When hydrates form they fill in the porous space in the sediments.
As early as 1890, scientists were studying clathrates. At that time they were considered a laboratory oddity, mostly because they often formed well above the freezing point of water. It wasn’t until 1930, when natural gas pipelines were extended into colder climates, that methane hydrates received more attention. Engineers discovered that water ice was not a problem for pipeline flow in the colder regions, the real culprit was methane hydrate. Even with this discovery, the clathrates were considered a nuisance rather than a resource.
In 1964, the attitude of laboratory oddity or engineering nuisance changed to one of potential energy resource when a Russian drilling crew in northern Siberia encountered naturally occurring methane hydrate. This frozen natural gas discovery started a worldwide search for more deposits. By the 1970s, methane hydrate had also been located in ocean sediments.
Most methane hydrate deposits in the U.S. are located in the Alaskan Outer Continental Shelf. Additional deposits are onshore in northern Alaska, in the Gulf of Mexico, and on the western and eastern outer continental shelves. The U.S. Geological Survey (USGS) estimates the U.S. to have about 200,000 trillion cubic feet of methane hydrate. This number dwarfs the estimated 1,400 trillion cubic feet of recoverable conventional methane from natural gas reserves and reservoirs. Worldwide estimates of methane hydrate deposits reach the overwhelming number of 400 million trillion cubic feet—far outdistancing the 5,500 trillion cubic feet of proven worldwide gas reserves.
The U.S. relies on natural gas for heating, cooking, transportation, industry and products. As national and worldwide supplies become more scarce, new resources for methane are a domestic priority. According to the U.S. Department of Energy, Office of Fossil Energy, “If only one 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.” To that end, Congress approved the Methane Hydrate Research and Development Program in 2000. This program has provided tens of millions of dollars in matching seed funds for research and development of methane hydrate as an energy resource. More recently, in November 2005, the U.S. Department of Energy announced $2 million in funding for five research projects focused on the energy potential, safety and environmental impacts of methane hydrate exploration and development.
Scientists are researching specific concerns about methane hydrate recovery and use which include drilling safety issues, potential influences on global climate change as methane is a potent greenhouse gas and the natural release of vast quantities from hydrate deposits would affect the global carbon cycle, cost effective transportation of the gas to the surface, and the possible impact of hydrate removal on ocean floor stability.
As natural gas supplies decrease and the demand for cleaner fuels increases, methane hydrates may well play a role in the U.S. energy portfolio.
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