Natural gas can be contained in a variety of different types of deposits that must be accessed if the natural gas is to be used. According to the Canadian Association of Petroleum Producers (CAPP), Canada has a natural gas reserve of between 700 and 1,300 trillion cubic feet. While a little over 15% of that natural gas has been recovered, the rest is contained in four types of deposits: conventional, and the so called unconventional deposits: Shale gas deposit, Tight gas deposit, and coal bed methane.
Natural gas has been extracted from conventional natural gas deposits for a long time, the unconventional resources are resources that are being extracted using substantially new techniques. Please see conventional vs unconventional resources.
Conventional resources are "pockets" of gas contained within relatively porous rock, and they are the most easily mined. While hydraulic fracturing has allowed for more expansive access to these deposits, they can be mined without its use.
Coal bed methane is natural gas consisting mostly of methane, which is trapped inside coal seams. This is extracted while the coal is being mined, as diminishing the pressure in the coal seam allows the gas to flow out of the seam and into a wellbore, where it is extracted.
Shale gas is natural gas found inside a fine-grained sedimentary rock called shale. Shale is porous (there are lots of tiny spaces inside it), but it is non-permeable, which means the gas cannot flow through it. Shale gas requires the use of hydraulic fracturing for extraction.
Tight gas is similar to shale gas in that it is trapped inside a porous, non-permeable reservoir rock. The only differentiation between the two is that the term tight gas includes natural gas trapped inside reservoir rocks that are not shale.