Natural Gas

Natural gas was formed millions of years ago when most of the earth was covered by water. Plant and tiny animal remains were mixed and layered with sand and mud. When the Earth underwent natural but drastic changes to form today’s landscape, the intense heat and pressure transformed these fossils into hydrocarbons—chemical compounds of hydrogen and carbon atoms. Natural gas is made up mainly of a chemical called methane, a simple, compound that has a carbon atom surrounded by four hydrogen atoms. Methane is highly flammable and burns almost completely. There is no ash and very little air pollution. Depending on the arrangement of the atoms, what were once sea plants and animals are now natural gas or crude oil deposits contained in the earth’s crust. Natural gas (a combustible, gaseous mixture of simple hydrocarbons) is a very light portion of petroleum, which includes both natural gas and crude oil. Natural gas may rise to the surface through natural openings in the earth’s crust or can be brought to the surface through man-made wells. Humans discovered thousands of years ago that this naturally occurring resource could be burned and used for heat and light.

In its natural state you can’t see or smell natural gas. It is colorless, odorless and lighter than air. Mercaptan, a chemical odorant, is added to natural gas so it can be smelled if it leaks. 

Natural gas is made up mostly of methane, which has a simple hydrocarbon structure of one carbon atom and four hydrogen atoms (CH4). This means it burns easily and emits less pollution. When natural gas is burned, it produces mostly carbon dioxide and water vapor.

Approximately 23 percent of the energy consumption of the U.S. comes from natural gas. Over one-half of the homes in the U.S. use natural gas as their main heating fuel.

Natural gas can be found in a variety of different underground formations, including: shale formations, sandstone beds, coal seams, and deep, salt water aquifers (underground ponds of water).

Natural gas is moved by pipelines from the producing fields to consumers. Since natural gas demand is greater in the winter, gas is stored along the way in large underground storage systems, such as old oil and gas wells or caverns formed in old salt beds. The gas remains there until it is added back into the pipeline when people begin to use more gas, such as in the winter to heat homes. When chilled to very cold temperatures, approximately -260 degrees Fahrenheit, natural gas changes into a liquid and can be stored in this form. Liquefied natural gas (LNG) can be loaded onto tankers (large ships with several domed tanks) and moved across the ocean to deliver gas to other countries. Once in this form, it takes up only 1/600th of the space that it would in its gaseous state. When this LNG is received in the United States, it can be shipped by truck to be held in large chilled tanks close to users or turned back into gas to add to pipelines.

U.S. Natural Gas Pipeline Network

The U.S. national natural gas transportation network delivered more than 23 trillion cubic feet of natural gas during 2008 to about 70 million customers. The network, excluding gathering system operators, is made up of more than 200 mainline transmission pipeline companies, more than 1,300 local distribution companies, and about 125 underground natural gas storage operators.

An intricate transportation system, made up of about 1.5 million miles of pipelines, links production areas and natural gas markets. Transporting natural gas from the production field to the consumer involves a series of steps, generally carried out in order:

• Gathering systems, primarily made up of small-diameter, low-pressure pipelines, move raw natural gas from the wellhead to a natural gas processing plant or to an interconnection with a larger mainline pipeline.
• Processing plants separate natural gas liquids and impurities from the natural gas stream before the natural gas is delivered into a mainline transmission system.
• About 306,000 miles of wide-diameter, high-pressure interstate and intrastate transmission pipelines transport natural gas from the producing area to market areas. Compressor stations (or pumping stations), located strategically along the length of the pipeline network, keep the natural gas flowing forward along the pipeline system.
• Underground storage facilities, fashioned from depleted oil, natural gas, or aquifer reservoirs or salt caverns, are used to store natural gas as a seasonal backup supply. When needed, this reserve is withdrawn to meet additional customer demand during peak usage periods. Aboveground liquefied natural gas storage facilities are also used for this purpose.
• Local distribution companies deliver natural gas to end users through hundreds of thousands of miles of small-diameter service lines. Local distribution companies reduce the pressure of the natural gas received from the high-pressure mainline transmission system to a level that is acceptable for use in residences and commercial establishments.

About 142,000 of the current 306,000 miles of the mainline natural gas transmission network was installed in the 1950s and 1960s as consumer demand for low-priced natural gas more than doubled following World War II. In fact, about half of the natural gas pipeline mileage currently installed in Texas and Louisiana, two of the largest natural gas production areas in the country, was constructed between 1950 and 1969. By the close of 1969, marketed natural gas production exceeded 20 trillion cubic feet for the first time.

A large portion of the 1.2 million miles of local distribution pipelines, which receive natural gas from the mainline transmission grid and deliver it to consumers, was also installed during the same period. However, the period of greatest local distribution pipeline growth has been more recent. In the 1990s, more than 225,000 miles of new local distribution lines were installed to provide service to the many new commercial facilities and housing developments that wanted access to lower-priced natural gas supplies during that period of economic growth.

The demand for natural gas has grown in recent years in part because it is considered a relatively environmentally-friendly energy source. Its use as an electric power generation fuel also has grown steadily with a decline in the capital costs of producing electric power from natural gas as technology in the area has improved.

Natural gas prices, along with oil prices, have increased substantially over the past 5 years. Higher prices gave natural gas producers the incentive to expand development of new natural gas fields. Consequently, new pipelines have been and are being built to link these new production sources to the existing mainline transmission network. Construction of new transmission and local distribution mainline pipeline mileage during the current decade, 2000-2009, is projected to surpass that of any other decade since the 1950s.

• Over one million miles of gas pipelines serve the United States

• Natural gas is the cleanest-burning fossil fuel

• Natural gas use has increased by 35 percent over the past ten years, and is projected to grow 45 percent by 2015.

• Ninety-nine percent of the natural gas used in the United States comes from North America.

• The U.S. gas distribution network is comprised of more than 1.2 miles of pipeline, supplying 175 million consumers.

• Natural gas provides 24 percent of all the energy used in the United States.

• About 55 percent of American homes use natural gas for heating.

• The first use of gas energy in the United States occurred in 1816, when gaslights illuminated the streets of Baltimore, Maryland.

credit: Energy Information Administration, U.S. Department of Energy, World Coal institute, OPEC, Shell Oil company