A primer for understanding Canadian shale gas : ABC du gaz de schistes au Canada

The principal Canadian shale gas plays are the Horn River Basin and Montney shales in northeast British Columbia, the Colorado Group of Alberta and Saskatchewan, the Utica Shale of Quebec, and the Horton Bluff Shale of New Brunswick and Nova Scotia. [...] In other words, the Barnett Shale is expected to produce the equivalent of almost one-third of Canada's 2008 natural gas production (458 106m3/d; 16.2 Bcf/d) or two-thirds of Canada’s 2008 natural gas consumption (216 106m3/d; 7.6 Bcf/d).8 Source of Natural Gas in Shale As mud turns into shale during shallow burial, generally just a few hundred metres deep, in the “nursery”, bacteria feed on the a [...] However, shale gas, both biogenic and thermogenic, remains where it was first generated and can be found in three forms: 1) free gas in the pore spaces and fractures; 2) adsorbed gas, where the gas is electrically stuck to the organic matter and clay; and 3) a small amount of dissolved gas that is dissolved in the organic matter. [...] The choice of the fluid used in a frac depends on many factors, including whether clay in the reservoir is sensitive to water (some clays swell in the presence of fresh water, such as in the Colorado Shale) or whether the reservoir happens to respond better to particular fluids, usually only determined through experimentation. [...] Overpressured shales develop during the generation of natural gas: because of the low permeability, much of the gas cannot escape and builds in place, increasing the internal pressure of the rock.