What is natural gas?

Natural gas is a naturally occurring mixture of hydrocarbons. It is colourless, shapeless and odourless. When burned, it produces energy in the form of heat and light. One of the primary components of natural gas is methane – the chemical compound CH₄ – one atom of carbon and four atoms of hydrogen.

Natural gas can also contain lesser amounts of ethane, propane, butane and condensates (also, referred to as natural gas liquids (NGL's)), and other substances such as carbon dioxide, nitrogen, sulfur compounds and helium.

Natural gas is created daily by both organic and inorganic processes. Natural gas is an abundant resource that is found in many environments across the earth. New technologies have unlocked vast quantities of this resource that have historically been uneconomic to recover.

Common components of uncompressed natural gas

How is natural gas formed?

Natural gas is formed in many different ways. Huge quantities of natural gas have been discovered in shale formations. These formations and their associated hydrocarbons formed millions of years ago when oceans covered much of the land that is now above sea level. The most prolific natural gas and NGL deposits have been created from shallow water marine environments. In these settings micro-organisms die and create a pelagic rain of organic material that accumulates over time at the bottom of the sea. Low oxygen levels allow for the preservation of this material. Enriched in these organic carbon components, these fine grained rocks become the sources for the vast majority of oil and gas fields on earth.

Over time the intense heat and pressure from these layers turned the sand and silt into sedimentary rock thousands of feet thick. This same heat and pressure chemically changed organic remains into natural gas and other petroleum products.

As natural gas began to migrate, it became trapped in rock pores and cracks like water in a sponge. Layers of less permeable, dense cap rock overlaying sedimentary formations prevent natural gas from reaching the surface.

With emergent technologies, these deposits once thought of as seals or source are now known to be vast reservoirs capable of producing some of the largest oil and gas fields found on earth.

Types of natural gas

Shale

Natural gas stored in extremely small pore spaces or bonded to organic material within rock composed mostly of consolidated clay, carbonate and siltstone.

Tight

Natural gas stored in small pore spaces in very low permeability underground formations, such as sandstone, siltstone or limestone.

Deep

Natural gas that's located deep within geological formations.

Coalbed methane

A sweet methane gas generated and stored in naturally occurring coal seams.

Natural gas liquids (NGL)

A combination of natural gas fluids associated with dry gas production, including ethane, propane, butanes, and condensate, which are light hydrocarbons that condense out of the fluid flow at the surface when the pressure and temperature fall from those in the reservoir.

Sweet gas

Raw natural gas with a relatively low concentration of sulfur compounds, such as hydrogen sulfide.

Sour gas

Raw natural gas with a relatively high concentration of sulfur compounds, such as hydrogen sulfide. All natural gas containing more than one percent hydrogen sulfide is considered sour.

How is natural gas found?

Today, exploration depends on the use of sophisticated technology to identify potential new sources of natural gas. The process for finding natural gas includes:

inspecting and mapping outcrop geology for surface features like the presence of sedimentary rock, potential reservoir rock, potential traps and hydrocarbon-bearing source rocks
examining all known geological information about the area, including surface observations, exploration results from adjacent areas and records from previous area wells
testing cuttings and core samples brought to the surface from the test well to measure age, chemistry, porosity, and permeability of the rock
measuring the wells flow rate to determine if economic quantities of natural gas are present; economic wells are then completed for production
running a seismic survey by transmitting acoustic energy into the earth and recording the energy reflected back to identify subsurface features; if seismic surveys identify potential economic structures, companies will drill a test well