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Major producing reserves are found in the Rocky Mountains, Texas and Louisiana. In addition, significant natural gas comes from offshore production in the Gulf of Mexico.
Improved technology has contributed to a 9 percent increase in U.S. natural gas production between 2007 and 2008. A trend toward horizontal drilling, in which the well bore turns from vertical to horizontal underground, allows access to natural gas deposits that cannot be reached vertically from the surface. Horizontal drilling into the Barnett Shale, a geologic formation under Fort Worth, Texas, helped contribute to that state's 15 percent increase in production.
Domestic reserves produced more than 20.6 trillion cubic feet (tcf) of natural gas delivered to market in 2008. That's equal to more than 88 percent of U.S. consumption.
Untapped Domestic Resources
At a time when we need all the energy we can find, increasing access to domestic sources of oil and natural gas would enhance our energy security. We have enough oil and natural gas resources to power 65 million cars for 60 years and heat 60 million households for 160 years.
There could be much more oil and natural gas than previously known in areas where industry has been unable to fully explore, and new technologies allow us to access resources previously thought unreachable. There are many examples of how the government’s initial estimates dramatically underestimated the amount of actual resources.
- Alaska’s Prudhoe Bay oilfield has produced more than 15 billion barrels of oil and natural gas liquids, and is still producing. Government agencies forecast the region would produce no more than 9 billion barrels, total.
- In the Bakken Formation of North Dakota and Montana, the U.S. Geological Survey now says 3 billion to 4 billion barrels of undiscovered oil are available - 25 times more than the original estimate made in 1995.
- In 1987, the MMs estimated that there were 9 billion barrels of oil in the Gulf of Mexico. By 2006, after major advances in seismic technology and deepwater drilling techniques, the MMS resource estimate for that area had ballooned to 45 billion barrels.
Processing and Delivery
Currently, over 95 percent of natural gas used in the United States moves from well to market entirely via a network of pipelines generally broken into three distinct systems:
- Gathering systems carry natural gas from individual wells for bulk processing at a treatment facility.
- Transmission systems carry the processed natural gas, often over long distances, from the producing region to local distribution systems around the country.
- Local distribution systems deliver natural gas into our homes, businesses and power plants.
Pipelines in the gathering and distribution systems range from 6" to 16" in diameter, with certain segments as narrow as 1/2". The pipes making up the interstate transmission system range in diameter from 16" to 48".
The natural gas used to cook our food and/or heat and cool our homes is 90 percent clean-burning methane, the simplest form of hydrocarbon. But that's not the case for natural gas as it comes out of the ground. Depending on the location of the well and the geologic conditions that created the gas in the first place, contaminants such as water, sulfur and natural gas liquids (including ethane, propane and butane) may be present. This makes it important to bring recovered natural gas into line with market specifications before it enters the main interstate pipeline system.
Some natural gas sources are too difficult or too expensive to reach via pipeline. Converting natural gas to liquid form - which occurs at approximately -260F - decreases its volume by more than 600 times and allows other transportation options, such as specially outfitted tanker ships and trucks, to be used.
Liquefied Natural Gas (LNG)
Liquefied Natural Gas (LNG) Natural gas converts to liquid form at approximately -260F°, decreasing its volume by more than 600 times. Liquefied natural gas (LNG) is transported in specially outfitted tanker ships and trucks to terminals where it is revaporized and sent to market through the traditional pipeline network.
The insulated tanks that store LNG use "auto refrigeration" to keep their contents cold. First, the natural gas is chilled to -260F° the temperature at which it condenses from gas to liquid. At that point, any heat gained from the atmosphere outside the tank is offset by the cooling effect of the resulting LNG evaporation within the tank. Any re-vaporized natural gas can be vented and recovered for use.
Demand
Natural gas heats 51 percent of U.S. homes, so consumer demand for natural gas increases during the colder months. Natural gas production, however, is essentially constant year round. Ten percent or more of the natural gas produced in periods of warmer weather is put into storage until demand increases.
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The current Annual Energy Outlook predicts a dip in demand from 2009-2010 until 2023-2024, then demand for natural gas will continue to grow.
Because natural gas consumption is affected by variations in price and trends in overall economic growth, the DOE's long-range projections address a number of different scenarios. For example, if economic growth is strong, natural gas consumption could be relatively unchanged in 2030 (24.01 Tcf). If economic growth is slower, consumption could decrease to 21.29 Tcf.
The electricity generation sector will be the main driver in long-term natural gas consumption trends. Economic growth will determine how much new generating capacity needs to be built. Also, because power plants can choose between energy sources, their natural gas consumption depends on the relative costs of natural gas and other fuels, such as coal.