Natural gas is one of the world's most important energy sources — cleaner-burning than coal or oil and used for everything from home heating to electricity generation. Chemically, it is dominated by one simple molecule: methane (CH4), a single carbon atom bonded to four hydrogen atoms.
Natural gas is mostly methane (CH4). It is found either associated (dissolved in or sitting on top of oil) or non-associated (in gas-only reservoirs). It is measured in cubic feet and must be processed before it can be used.
Associated vs non-associated gas
Natural gas occurs in two main settings:
- Associated gas is found together with oil — dissolved in the crude or forming a gas cap above it. It is produced as a byproduct of oil production.
- Non-associated gas comes from reservoirs that hold gas with little or no oil. These are developed specifically for their gas.
The simplest hydrocarbon and the main component of natural gas. When processed and delivered to a pipeline, the gas is almost pure methane.
How natural gas is measured
Unlike oil, which is measured in barrels, natural gas is measured by volume in cubic feet. Because the quantities are so large, the industry uses shorthand multiples: Mcf (thousand cubic feet), MMcf (million), Bcf (billion) and Tcf (trillion). Gas is also valued by its energy content in BTUs. See our units guide for the full breakdown, or convert volume to energy with the Mcf to MMBtu converter.
From raw gas to fuel
Gas straight from a well is not ready to use. Raw gas is processed to remove water, impurities such as hydrogen sulfide and CO2, and the heavier natural gas liquids, leaving clean pipeline-quality methane. (See natural gas processing for how that works.)
What natural gas is used for
- Heating — homes, businesses and industrial processes.
- Power generation — fueling gas-fired electricity plants.
- Feedstock — a raw material for fertilizers, plastics and chemicals.
- LNG export — chilled to a liquid and shipped overseas by tanker.
Together these uses make natural gas a versatile bridge fuel central to the modern energy system.
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Frequently asked
Natural gas is mostly methane (CH4). Raw gas also contains water, heavier hydrocarbons (natural gas liquids) and impurities, which are removed during processing to leave nearly pure methane.
Associated gas is produced together with oil — dissolved in it or as a gas cap above it. Non-associated gas comes from reservoirs that hold gas with little or no oil.
Natural gas is measured by volume in cubic feet, using multiples like Mcf (thousand), MMcf (million), Bcf (billion) and Tcf (trillion), and by energy content in BTUs.