Types of natural gas deposits

Natural gas can be found in a variety of different types of deposits that can be accessed for production.Natural gas occurs in four main types of deposits: conventional natural gas deposits and the three major unconventional deposits: shale gas, tight gas, and coal bed methane.

Natural gas has been extracted from conventional natural gas deposits for many decades, whereas unconventional natural gas resources require specialized extraction techniques such as horizontal drilling and hydraulic fracturing. See conventional vs unconventional resources for more information.

Conventional natural gas deposits

Conventional natural gas resources are accumulations of gas trapped within relatively porous and permeable rock formations, making them the easiest type of natural gas deposit to produce. Although hydraulic fracturing has expanded access to some conventional natural gas deposits, conventional reservoirs can often be produced without its use.

Coal bed methane

Coalbed methane is natural gas consisting primarily of methane that is trapped within coal seams. Coalbed methane is produced by reducing the pressure within the coal seam allowing the gas to flow into a wellbore for collection. It may be extracted before, during, or independently of coal mining, depending on the location and the intended use of the coal seam.

Shale gas

Shale gas is natural gas found within a fine-grained sedimentary rock called shale. Shale is porous (t contains many tiny spaces), but it is has very low permeability, meaning the gas cannot flow through it easily. Shale gas typically requires hydraulic fracturing to be produced economically.

Tight gas

Tight gas is similar to shale gas in that it is trapped inside a porous reservoir rock with very low permeability. The main difference is that tight gas refers to natural gas trapped within low permeability reservoir rocks that are not shale, such as sandstone or carbonate formations.