Domestic natural gas production in the United States has expanded dramatically because of a technology known as “hydraulic fracturing” (sometimes called hydrofracking or fracking) that makes retrieving natural gas from shale formations more cost effective, particularly as demand for the fuel grows.
History of shale gas production
Shale gas has been produced for more than 100 years in the Appalachian (eastern states) and Illinois shale (central states) basins of the United States. Until recently these operations were only marginally profitable, primarily because shale gas wells generally cost more to produce than conventional wells.
Over recent years, however, higher natural gas prices and advances in shale gas production methods have improved profitability. Since the early 21st century, shale gas basins in Wyoming, Texas, and New York have witnessed a boom in production.
Harvesting gas from solid rock
Most shale gas wells are drilled vertically, straight down as far as 10,000 feet, to reach shale formations. Then the drill bit is turned horizontally and the well is extended laterally into the rock. After the well is drilled, hydraulic fracturing begins.What is fracking sand?
During the this "fracking" process, millions of gallons of water, sand, and chemicals are pumped under high pressure into the well to break apart the rock, release the gas, and force it out of the rock and into the well to the surface where it’s captured. Fracking (also known as hydrofracking, fracing, and fraccing) is the predominant process used to extract gas from shale formations in the United States.
Abundant supply nationwide
Geologists have discovered more than two dozen producing and potential shale gas formations across the country in Rocky Mountain and Appalachian Mountain states; the Dakotas, Kansas, Nebraska, Texas, Oklahoma, Arkansas and Louisiana; as well as Illinois, Indiana, Kentucky, Ohio, and Wisconsin.
The most explored and produced plays are the Barnett Shale (Texas), the Haynesville/Bossier Shale (Louisiana, Texas), the Antrim Shale (Michigan), the Fayetteville Shale (Arkansas), the Marcellus Shale (New York, Ohio, Pennsylvania, West Virginia) and the New Albany Shale (Indiana, Kentucky). Analysts have estimated that most growth in natural gas reserves will come from shale plays.
The total estimated recoverable gas resources from just four of these plays – Haynesville, Fayetteville, Marcellus and Woodford – may be over 550 trillion cubic feet (TCF), which alone amounts to about a 20-year supply considering current total American consumption of about 23 TCF per year.
Expanding shale gas activities
Natural gas provides about 25 percent of total U.S. energy. About 30 percent of the total natural gas production is from shale resources, which has expanded rapidly from less than 2 percent of total U.S. production of natural gas in 2001, according to a report published Aug. 18, 2011, by the Shale Gas Production Subcommittee of the Secretary of Energy Advisory Board.
Expansion of shale gas production began to be widely recognized around 2008. Output since then has increased four-fold with production growing in new regions such as the Haynesville shale, mostly in Louisiana, which produced negligible amounts in 2008. Now Haynesville produces 8 percent of total U.S. natural gas.
The U.S. Energy Information Administration (EIA) predicts further rapid expansion of shale gas production, projecting shale gas to be 46 percent of domestic production by 2035. With the growth in U.S. production of shale gas, interest has spread to potential gas shale basins in Canada, Europe, Asia, and Australia.
How shale gas is formed
Shale basins are large underground deposits of fined-grained sedimentary shale rock formed from silt and mud compacted over a very long time. Deposits are built up in layers, much like plywood is laminated.
Early in this millennia-long process, tiny particles of organic matter deposited with the mud warmed within the earth and over time was converted into oil and natural gas. Some of the oil and natural gas seeped from the shale up through the sediment. The oil and gas often were trapped in the pore spaces of an overlying rock formation such as sandstone. These petroleum deposits are known as "conventional reservoirs" because the oil and gas can easily flow through the rock pores and into a “conventional” extraction well.
However, large amounts of oil and natural gas remain trapped within the shale deep under the earth’s surface. Though this oil and gas is more difficult to remove, horizontal drilling and “hydraulic fracturing” have been very successful in exploiting this these resources.