Skip to page content


Natural Gas

Energy Ant

File Scrub 1 ::::: EE ... natural_gas_home-basics

Natural Gas Basics

What is natural gas?

Natural gas occurs deep beneath the earth's surface. Natural gas consists mainly of methane, a compound with one carbon atom and four hydrogen atoms. Natural gas also contains small amounts of hydrocarbon gas liquids and nonhydrocarbon gases. We use natural gas as a fuel and to make materials and chemicals.

How did natural gas form?

Millions of years ago, the remains of plants and animals (diatoms) decayed and built up in thick layers, sometimes mixed with sand and silt. Over time, these layers were buried under sand, silt, and rock. Pressure and heat changed some of this organic material into coal, some into oil (petroleum), and some into natural gas. In some places, the natural gas moved into large cracks and spaces between layers of overlying rock. In other places, natural gas occurs in the tiny pores (spaces) within some formations of shale, sandstone, and other types of sedimentary rock, where it is referred to as shale gas or tight gas. Natural gas also occurs in coal deposits, which is called coalbed methane.

Three images, all about Petroleum & Natural Gas Formation.

The first image is about the Ocean 300 to 400 million years ago. Tiny sea plants and animals died and were buried on the ocean floor. Over time, they were covered by layers of sand and silt.

The second image is about the Ocean 50 to 100 million years ago. Over millions of years, the remains were buried deeper and deeper. The enormous heat and pressure turned them into oil and gas.

The third image is about Oil & Gas Deposits. Today, we drill down through layers of sand, silt, and rock to reach the rock formations that contain oil and gas deposits.
Click to enlarge »

Source: U.S. Energy Information Administration (public domain)

In some places, gas escapes from small gaps in the rocks into the air; then, if there is enough activation energy from lightning or a fire, it burns. When people first saw the flames, they experimented with them and learned they could use them for heat and light.

How do we get natural gas?

Did you know?

Because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). This added odor serves as a safety measure to help detect leaks in natural gas pipelines.

Operators preparing a hole for the explosive charges used in seismic exploration
Operators Preparing a Hole for the Explosive Charges Used in Seismic Exploration

Source: Stock photography (copyrighted)

The search for natural gas begins with geologists who study the structure and processes of the earth. They locate the types of rock that are likely to contain natural gas deposits. Some of these areas are on land and some are offshore and deep under the ocean floor.

Geologists often use seismic surveys on land and in the ocean to find the right places to drill wells. Seismic surveys on land use echoes from a vibration source at the surface of the earth, usually a vibrating pad under a special type of truck. Geologists can also use small amounts of explosives as a vibration source. Seismic surveys conducted in the ocean rely on blasts of sound that create sonic waves to explore the geology beneath the ocean floor.

If a site seems promising, an exploratory well is drilled and tested. Once a formation is proven to be economic for production, one or more production (or development) wells are drilled down into the formation, and natural gas flows up through the wells to the surface. In the United States and a few other countries, natural gas is produced directly from shale and other types of rock formations that contain natural gas in pores within the rock. The rock formation is fractured by forcing water, chemicals, and sand down a well. This releases the natural gas from the rock, and the natural gas flows up the well to the surface. Wells drilled to produce oil may also produce associated natural gas.

Coal may contain coalbed methane, which can be captured when coal is mined. Coalbed methane can be added to natural gas pipelines without any special treatment. Another source of methane is biogas, which forms in landfills and in vessels called digesters.

Most of the natural gas consumed in the United States is produced in the United States. Some natural gas is imported from Canada and Mexico in pipelines. A small amount of natural gas is also imported as liquefied natural gas.

File Scrub L3 ::::: EE ... natural_gas_home-basics ... natural_gas_delivery-basics

Getting Natural Gas to Users

Transporting natural gas involves several steps

Transporting natural gas from the wellhead to consumers requires many infrastructure assets and processing steps, and it includes several physical transfers of custody.

Natural gas delivery infrastructure can be grouped into three categories:

  • Processing
  • Transportation
  • Storage

A generalized natural gas industry process flow diagram that goes from the well to the consumer.

Processing natural gas for transportation by pipeline

Natural gas transported on the mainline natural gas transportation system in the United States must meet specific quality measures so that the pipeline network (or grid) can provide uniform quality gas. Wellhead natural gas may contain contaminants and hydrocarbon gas liquids (HGL) that must be removed before the natural gas can be safely delivered to the high-pressure, long-distance pipelines that transport natural gas to consumers.

A natural gas processing plant typically receives natural gas from a gathering system of pipelines from natural gas and oil wells. Natural gas processing can be complex and usually involves several processes, or stages, to remove oil, water, hydrocarbon gas liquids, and other impurities such as sulfur, helium, nitrogen, hydrogen sulfide, and carbon dioxide. The composition of the wellhead natural gas determines the number of stages and the process required to produce pipeline-quality dry natural gas. These processes or stages may be integrated into one unit or operation, be performed in a different order or at alternative locations (lease/plant), or not be required at all.

The basic stages of natural gas processing/treatment are

  • Gas-oil-water separators: Pressure relief in a single-stage separator causes a natural separation of the liquids from the gases in the natural gas. In some cases, a multi-stage separation process is required to separate the different fluid streams.
  • Condensate separator: Condensates are most often removed from the natural gas stream at the wellhead with separators much like gas-oil-water separators. The gas flow into the separator comes directly from the wellhead. Extracted condensate is sent to storage tanks.
  • Dehydration: A dehydration process removes water that may cause the formation of undesirable hydrates and water condensation in pipelines.
  • Contaminant removal: Nonhydrocarbon gases—such as hydrogen sulfide, carbon dioxide, water vapor, helium, nitrogen, and oxygen—must also be removed from the natural gas stream. The most common removal technique is to direct the natural gas though a vessel containing an amine solution. Amines absorb hydrogen sulfide and carbon dioxide from natural gas and can be recycled and regenerated for repeated use.
  • Nitrogen extraction: Once the hydrogen sulfide and carbon dioxide are reduced to acceptable levels, the natural gas stream is routed to a Nitrogen Rejection Unit (NRU), where it is further dehydrated using molecular sieve beds.
  • Methane separation: The process of demethanizing the natural gas stream can occur as a separate operation in a natural gas processing plant or as part of the NRU operation. Cryogenic processing and absorption methods are some of the ways used to separate methane from HGL.
  • Fractionation: Fractionation separates the HGL into component liquids using the varying boiling points of the individual HGL. HGL from the processing plant may be sent to petrochemical plants, oil refineries, and other HGL consumers.

Pipelines move natural gas from production fields to markets

Natural gas transmission pipelines are wide-diameter pipelines. They are often the long-distance portion of natural gas pipeline systems that connect gathering systems in producing areas, natural gas processing plants, other receipt points, and the main consumer service areas. The three types of transmission pipelines are:

  • Interstate natural gas pipelines operate and transport natural gas across state borders.
  • Intrastate natural gas pipelines operate and transport natural gas within a state border.
  • Hinshaw natural gas pipelines receive natural gas from interstate pipelines and deliver it to consumers for consumption within a state border.

When natural gas arrives at the communities where it will be used (usually through large pipelines), it flows into smaller diameter pipelines called mains and then into smaller service lines that go directly to homes or buildings.

Natural gas can also be stored for times of peak demand

Demand for natural gas fluctuates daily and seasonally, while production and pipeline imports are relatively constant in the short term. Storage of natural gas during periods of low demand helps to ensure that sufficient supplies of natural gas are available during periods of high demand. Natural gas is stored in large volumes in underground facilities and in smaller volumes in tanks above and below ground.

The United States uses three main types of natural gas underground storage facilities:

  • Depleted natural gas or oil fields that are close to consuming areas is where most of the natural gas is stored in the United States.
  • Salt caverns provide high withdrawal and injection rates relative to their working natural gas capacity. Base natural gas requirements are relatively low. Most of the salt cavern storage facilities are in salt dome formations in the Gulf Coast states. Salt caverns have also been leached from bedded salt formations in states in the Midwest, Northeast, and Southwest.
  • Aquifers that are converted to natural gas storage reservoirs, most notably in the Midwest. An aquifer is suitable for natural gas storage if the water-bearing sedimentary rock formation is overlaid with an impermeable cap rock.

File Scrub L3 ::::: EE ... natural_gas_home-basics ... natural_gas_lng-basics

What is Liquefied Natural Gas?

Liquefied natural gas (LNG) is natural gas that has been cooled to a liquid state, at about -260°Fahrenheit, for shipping and storage. The volume of natural gas in its liquid state is about 600 times smaller than its volume in its gaseous state. This process, which was developed in the 19th century, makes it possible to transport natural gas to places pipelines do not reach.

The United States imports and exports LNG. Sometimes, LNG originally imported to the United States is re-exported to other destinations where prices are higher. In 2016, the United States imported about 88 billion cubic feet (Bcf) of LNG. All LNG imports were from Trinidad and Tobago (95%), Norway (4%), and Canada (1%).

In 2016, the U.S. exported about 187 Bcf of LNG to 18 countries, which included about 3 Bcf of re-exported LNG. Nearly all LNG exports were by vessel (tanker ships). A small amount was exported by truck to Canada and Mexico.

The top 5 destination countries and shares of total U.S. LNG exports in 2016

  • Chile—16%
  • Mexico—15%
  • India—9%
  • Argentina—9%
  • China—9%

Interest in using LNG as a fuel for heavy-duty vehicles, ocean tankers, and other transportation applications is on the rise.

File Scrub L3 ::::: EE ... natural_gas_home-basics ... natural_gas_where-basics

Where Our Natural Gas Comes From

The United States now produces nearly all of the natural gas that it uses

U.S. natural gas production in 2016 was the second-highest level recorded, down slightly from 2015, which has the highest-recorded production level. Production increases since 2005 have mainly been the result of horizontal drilling and hydraulic fracturing techniques, notably in shale, sandstone, carbonate, and other tight geologic formations. Natural gas is produced from onshore and offshore natural gas and oil wells and from coal beds. In 2016, U.S. dry natural gas production was equal to about 97% of U.S. natural gas consumption.

Five states accounted for about 65% of total U.S. dry natural gas production in 2016:

  • Texas—24%
  • Pennsylvania—20%
  • Oklahoma—9%
  • Louisiana—6%
  • Wyoming—5%

What is shale?

Shale is a fine-grained sedimentary rock that forms when silt and clay-size mineral particles are compacted, and it is easily broken into thin, parallel layers. Black shale contains organic material that can generate oil and natural gas, which is trapped within the rock's pores.

Offshore natural gas production

Although most of the natural gas and oil wells in the United States are on land, some wells are drilled into the ocean floor in waters off the coast of the United States. Most of U.S. offshore natural gas production occurs in federal waters in the Gulf of Mexico, the source of about 4% of U.S. dry natural gas production in 2016.

Coalbed methane and supplemental gaseous fuels

The United States obtains methane from coal beds. In 2016, U.S. coalbed methane production was equal to about 4% of total U.S. natural gas consumption.

Supplemental gaseous fuels include blast furnace gas, refinery gas, biomass gas, propane-air mixtures, and synthetic natural gas (natural gas made from petroleum hydrocarbons or from coal). These supplemental supplies were equal to about 0.2% of U.S. natural gas consumption in 2015. The largest source of synthetic natural gas is the Great Plains Synfuels Plant in Beulah, North Dakota, where coal is converted to pipeline-quality natural gas. {/ee}

File Scrub L3 ::::: EE ... natural_gas_home-basics ... natural_gas_imports-basics

Natural Gas Imports and Exports

Although most of the natural gas consumed in the United States is produced domestically, the United States is a net importer of natural gas, meaning that it imports more natural gas than it exports.

The United States has relied less on natural gas imports in recent years, mainly because of increases in U.S. natural gas production. U.S. net imports of natural gas peaked in 2007. In 2016, the United States imported about 3 trillion cubic feet (Tcf) of natural gas and exported about 2.3 Tcf, resulting in net imports of about 0.7 Tcf.1 In 2016, net imports (imports minus exports) of natural gas were equal to about 3% of U.S. natural gas consumption.

Did you know?

Natural gas is transported on specially designed ships as liquefied natural gas (LNG). LNG is natural gas that is cooled to -260┬░Fahrenheit at which point the gas becomes a liquid. The volume of the liquid is 600 times smaller than the gaseous form.

Most natural gas imports and exports are by pipeline as a gas and by ship as liquefied natural gas (LNG). Small amounts of natural gas are also exported on trucks as LNG and as compressed natural gas (CNG)..

In 2016, 97% of U.S. net imports of natural gas came by pipeline, and 3% came in LNG ships from around the world. A small amount came as compressed natural gas (CNG) from Canada.

Pipeline imports of natural gas are mostly from Canada

In 2016, nearly all of U.S. pipeline imports of natural gas were from Canada. Less than 1% of natural gas pipeline imports were from Mexico.

LNG imports are a small share of total U.S. natural gas imports and consumption

In 2016, imports of LNG totaled about 0.09 Tcf. About 95% of the LNG imports were from Trinidad and Tobago, 4% were from Norway, and 1% were from Canada.

Most U.S. natural gas exports go to Canada and Mexico by pipeline

U.S. exports of natural gas reached a record high in 2016. In 2016, pipeline exports accounted for 92% of U.S. natural gas exports. Canada received 36% of U.S. pipeline natural gas exports, and Mexico received 64%.

The United States also exports LNG and CNG. In 2016, U.S. exports of LNG and CNG accounted for about 8% of total U.S. exports of natural gas.

1 Preliminary data for 2016.
File Scrub L3 ::::: EE ... natural_gas_home-basics ... natural_gas_use-basics

Uses of Natural Gas

The United States used about 27.49 trillion cubic feet (Tcf) of natural gas in 2016, the equivalent of 28.4 quadrillion British thermal units (Btu) and 29% of total U.S. energy consumption.

Natural gas use by U.S. consuming sectors by amount and share of total U.S. natural gas consumption in 2016:

  • Electric power—9.987 Tcf—36%
  • Industrial—9.31 Tcf—34%
  • Residential—4.35 Tcf—16%
  • Commercial—3.11 Tcf—11%
  • Transportation—0.74 Tcf—3%

How natural gas is used in the United States

Most U.S. natural gas use is for heating buildings and generating electricity, but some consuming sectors have other uses for natural gas.

The electric power sector uses natural gas to generate electricity. In 2016, the electric power sector accounted for about 36% of U.S. natural gas consumption, and natural gas was the source of about 27% of the U.S. electric power sector's energy consumption. (Other consuming sectors also use natural gas to generate electricity.)

The industrial sector uses natural gas as a fuel for process heating and for combined heat and power systems and as a raw material (feedstock) to produce chemicals, fertilizer, and hydrogen. In 2016, the industrial sector accounted for about 34% of U.S. natural gas consumption, and natural gas was the source of about 31% of the U.S. industrial sector's energy consumption.

The residential sector uses natural gas to heat buildings and water, to cook, and to dry clothes. About half of the homes in the United States use natural gas for these purposes. In 2016, the residential sector accounted for about 16% of U.S. natural gas consumption, and natural gas was the source of about 22% of the U.S. residential sector's energy consumption.

The commercial sector uses natural gas to heat buildings and water, to operate refrigeration and cooling equipment, to cook, to dry clothes, and to provide outdoor lighting. Some consumers in the commercial sector also use natural gas as a fuel in combined heat and power systems. In 2016, the commercial sector accounted for about 11% of U.S. natural gas consumption, and natural gas was the source of about 18% of the U.S. commercial sector's energy consumption.

The transportation sector uses natural gas as a fuel to operate compressors that move natural gas through pipelines. A relatively small amount of natural gas is used as vehicle fuel in the form of compressed natural gas and liquefied natural gas. Nearly all vehicles that use natural gas as a fuel are in government and private vehicle fleets. In 2016, the transportation sector accounted for about 3% of total U.S. natural gas consumption. Natural gas was the source of about 3% of the U.S. transportation sector's energy consumption in 2016, of which 97% was for natural gas pipeline and distribution operations.

Where natural gas is used

Natural gas is used throughout the United States, but five states accounted for about 39% of total U.S. natural gas consumption in 2016:

  • Texas—14.7%
  • California—7.90%
  • Louisiana—5.7%
  • New York—5.0%
  • Florida—4.8%

File Scrub L3 ::::: EE ... natural_gas_home-basics ... natural_gas_environment-basics

Natural Gas & the Environment

Natural gas well drilling operation
Natural Gas Well Drilling Operation

Source: Bureau of Land Management (public domain)

Did you know?

Advanced technologies like satellites, global positioning systems, remote sensing devices, and 3-D and 4-D seismic technologies make it possible to discover natural gas reserves while drilling fewer wells.

Natural gas has many qualities that make it an efficient, relatively clean burning, and economical energy source. However, the production and use of natural gas have some environmental and safety issues to consider.

Natural gas is a relatively clean burning fossil fuel

Burning natural gas for energy results in fewer emissions of nearly all types of air pollutants and carbon dioxide (CO2) than burning coal or petroleum products to produce an equal amount of energy. About 117 pounds of carbon dioxide are produced per million British thermal units (MMBtu) equivalent of natural gas compared with more than 200 pounds of CO2 per MMBtu of coal and more than 160 pounds per MMBtu of distillate fuel oil. The clean burning properties of natural gas have contributed to increased natural gas use for electricity generation and as a transportation fuel for fleet vehicles in the United States.

Natural gas is mainly methane—a strong greenhouse gas

Some natural gas leaks into the atmosphere from oil and natural gas wells, storage tanks, pipelines, and processing plants. These leaks were the source of about 32% of total U.S. methane emissions and about 4% of total U.S. greenhouse gas emissions in 20151. The oil and natural gas industry takes steps to prevent natural gas leaks.

Natural gas exploration, drilling, and production affects the environment

When geologists explore for natural gas deposits on land, they may disturb vegetation and soil with their vehicles. Drilling a natural gas well on land may require clearing and leveling an area around the well site. Well drilling activities produce air pollution and may disturb people, wildlife, and water resources. Laying pipelines that transport natural gas from wells usually requires clearing land to bury the pipe. Natural gas production can also produce large volumes of contaminated water. This water requires proper handling, storage, and treatment so that it does not pollute land and other waters. Natural gas wells and pipelines often have engines to run equipment and compressors, which produce air pollutants and noise.

In areas where natural gas is produced at oil wells but is not economical to transport for sale or contains high concentrations of hydrogen sulfide (a toxic gas), it is burned (flared) at well sites. Natural gas flaring produces CO2, carbon monoxide, sulfur dioxide, nitrogen oxides, and many other compounds, depending on the chemical composition of the natural gas and on how well the natural gas burns in the flare. However, flaring is safer than releasing natural gas into the air and results in lower overall greenhouse gas emissions because CO2 is not as strong a greenhouse gas as methane.

Advances in drilling and production technologies have positive and negative effects on the environment

New drilling and natural gas recovery technologies significantly reduce the land area that is disturbed to develop oil and gas resources. Horizontal and directional drilling techniques make it possible to produce more natural gas from a single well than in the past, so fewer wells are necessary to develop a natural gas field.

Hydraulic fracturing (commonly called hydrofracking, fracking, or fracing) of shale, sandstone, and carbonate rock formations is opening up large reserves of natural gas that were previously too expensive to develop. Fracking involves pumping liquids under high pressure into a well to fracture the rock, which allows natural gas to escape from the rock. Producing natural gas with this technique has some effects on the environment:

  • The fracturing of wells requires large amounts of water. In some areas of the country, significant use of water for fracking may affect aquatic habitats and the availability of water for other uses.
  • If mismanaged, hydraulic fracturing fluid—which may contain potentially hazardous chemicals—could be released through spills, leaks, faulty well construction, or other exposure pathways. These releases could contaminate surrounding areas.
  • Hydraulic fracturing produces large amounts of wastewater at the surface, which may contain dissolved chemicals and other contaminants that require treatment before disposal or reuse. Because of the quantities of water produced and the complexities inherent in treating some of the wastewater components, proper treatment and disposal of the wastewater is important.
  • According to the U.S. Geological Survey, hydraulic fracturing "...causes small earthquakes, but they are almost always too small to be a safety concern. In addition to natural gas, fracking fluids and formation waters are returned to the surface. These wastewaters are frequently disposed of by injection into deep wells. The injection of wastewater into the subsurface can cause earthquakes that are large enough to be felt and may cause damage."
  • Natural gas could be released to the atmosphere during and after well drilling, and the amount of these releases are under investigation.

Natural gas production, transportation, distribution, and storage require strict safety regulations and standards

Because a natural gas leak could cause an explosion, strict government regulations and industry standards are in place to ensure the safe transportation, storage, distribution, and use of natural gas. Because processed natural gas has no odor, natural gas companies add a strong, rotten egg-like smelling substance called mercaptan to natural gas so that people can smell leaks.

1Based on carbon-dioxide equivalents.