Natural gas

Natural gas are a type of natural resource which are hydrocarbons that exist as a gas or vapor at ordinary pressures and temperatures.

Methane is the most important, but ethane, propane, or others may be present.

Natural gas production world

Fossil energy

Natural gas is a fossil energy source that formed deep beneath the earth's surface and contains many different compounds.

Methane

The largest component of natural gas is methane, a compound with one carbon atom and four hydrogen atoms (CH4).

Formation

Millions of years(or hundreds of millions) ago and over long periods of time, the remains of plants and animals (such as diatoms) built up in thick layers on the earth’s surface and ocean floors, sometimes mixed with sand, silt, and calcium carbonate.

Gradually, these layers were buried under sand, silt, and rock. Pressure and heat changed some of this carbon and hydrogen-rich material into coal, some into oil (petroleum), and some into natural gas.

Types of natural gas

In some places, natural gas moved into large cracks and spaces between layers of overlying rock.

Darvasa gas crater

Conventional natural gas

The natural gas found in these types of formations is sometimes called conventional natural gas.

Shale gas

In other places, natural gas occurs in the tiny pores (spaces) within some formations of shale, sandstone, and other types of sedimentary rock. This natural gas is referred to as shale gas or tight gas, and it is sometimes called unconventional natural gas.

Associated natural gas

Natural gas also occurs with deposits of crude oil, and this natural gas is called associated natural gas.

Coalbed methane

Natural gas deposits are found on land, and some are offshore and deep under the ocean floor. A type of natural gas found in coal deposits is called coalbed methane.

Health and environmental concerns

The natural gas industry is a significant source of emissions of methane, a potent greenhouse gas with a global warming potential more than 25 times that of carbon dioxide.

Volatile organic compounds

It also is the largest industrial source of emissions of volatile organic compounds (VOCs), a group of chemicals that contribute to the formation of ground-level ozone (smog). Exposure to ozone is linked to a wide range of health effects, including aggravated asthma, increased emergency room visits and hospital admissions, and premature death.

In addition to helping form ozone, these VOC emissions from the oil and gas industry include air toxics such as benzene, ethylbenzene, and n-hexane, also come from this industry. Air toxics are pollutants known, or suspected of causing cancer and other serious health effects.