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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, where it 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 & natural gas deposits. Today, we drill down through layers of sand, silt, and rock to reach the rock formations that contain oil and natural gas deposits.

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

How do we get natural gas?

Did you know?

Because natural gas is colorless, odorless, and tasteless, natural gas companies add mercaptan to natural gas to give it a distinct and unpleasant odor to help detect leaks in natural gas pipelines. Mercaptan is a harmless chemical that smells like rotten eggs.

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 oil and natural gas 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 process 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.

The natural gas withdrawn from a well is called wet natural gas because it usually contains liquid hydrocarbons and nonhydrocarbon gases. Methane and other useful gases are separated from the wet natural gas near the site of the well or at a natural gas processing plant. The processed natural gas is called dry or consumer-grade natural gas. This natural gas is sent through pipelines to underground storage fields or to distribution companies and then to consumers.

Coal deposits 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.

Last updated: October 31, 2018

Natural gas statistics

Data for the United States for 2017, except where noted. Physical amounts (volumes) are in billion cubic feet (Bcf) and prices are in dollars per thousand cubic feet (Mcf).

U.S. production (dry gas) 27,291 Bcf
U.S. consumption 27,110 Bcf
U.S. imports  3,042 Bcf
U.S. exports  3,168 Bcf
Average citygate price  $4.16 per Mcf
Average price delivered to consumers
  • $10.91 per Mcf
  •  $7.88 per Mcf
  •  $4.10 per Mcf
  •  $3.52 per Mcf
Ranking of state residential prices

Highest—Hawaii—$38.88 per Mcf

Lowest—Montana—$7.62 per Mcf

Natural gas consumption by end use Amount—share of total
  • 9,250 Bcf—34%
  • 7,949 Bcf—29%
  • 4,412 Bcf—16%
  • 3,164 Bcf—12%
  • 1,564 Bcf—6%
  •    770 Bcf—3%
Liquefied natural gas (LNG) imports 78 Bcf
Number of producing natural gas wells 486,258
Natural gas percentage of utility-scale electricity generation 32%
Natural gas percentage of utility-scale electricity generation capacity (2016) 42%
Top natural gas-producing state Texas
World dry natural gas production(2015) 124,258 Bcf
World consumption(2015) 124,866 Bcf

Last updated: October 10, 2018