The Horn River Formation is composed of dark siliceous and calcareous shale, and argillaceous bituminous limestone.

[2] It is subdivided into the following members, from top to base: The Horn River Formation is present in the subsurface in northeastern British Columbia and extends to Great Slave Lake in the Northwest Territories, where it outcrops.

[2] It reaches a maximum thickness of 320 metres (1,050 ft) in the subsurface of the Fort Nelson area.

Horizontal drilling and fracturing techniques are used to extract the gas from the low permeability shales.

[8] The original-gas-in-place volumes are estimated to be up to 500 Tcf,[9] making it the third largest North American natural gas accumulation discovered prior to 2010.