This section provides an overview for natural gas:
Raw natural gas consists mostly of methane and other hydrocarbon gases, but it also contains nonhydrocarbons, such as nitrogen, carbon dioxide, and hydrogen sulphide (H2S). These impurities typically make up less than 10 per cent of raw natural gas. The estimated average composition of the hydrocarbon component without impurities is about 92 per cent methane, 5 per cent ethane, and lesser amounts of propane, butanes, and pentanes plus.
Alberta’s natural gas has a wide spectrum of components, and gas varieties range from dry gas to liquids-rich gas. Dry gas generally consists of mostly methane with some examples being shallow gas pools located in southeast Alberta and coalbed methane (CBM) deposits in central Alberta. Gas with small amounts of extractable liquids is referred to as lean gas, whereas gas with larger amounts is called wet gas. Liquids-rich gas refers to natural gas that contains an unusually high amount of liquids. Pools containing liquids-rich gas are often found along the front of the foothills of the province.
Marketable gas is the gas that remains after the raw gas is processed to remove nonhydrocarbons and heavier natural gas liquids and that meets specifications for use as a fuel. Natural gas volumes are referred to as either the actual metered volume with the combined heating value of the hydrocarbon components present in the gas (i.e., “as is” gas) or the volume at standard conditions of 37.4 megajoules per cubic metre (MJ/m3). The average heat content of produced conventional natural gas leaving field plants is estimated to be 39.2 MJ/m3. This compares with a heat content of about 37.0 MJ/m3 for CBM.
This section discusses both conventional and unconventional natural gas, with unconventional gas including “tight,” CBM, and shale gas. Tight gas refers to natural gas found in low-permeability rock, including sandstone, siltstone, and carbonates. Shale gas is natural gas locked in fine-grained, organic-rich rock. CBM is methane found in coal, both as adsorbed gas and free gas. It is often difficult or impossible to separate the tight portion of the reserves or production of a conventional reservoir. Therefore, unconventional tight gas volumes are included within the AER’s conventional natural gas reserves and production reporting.