Summarising the general characteristics and differences of shale gas and coal bed methane deposits

Term Shale Gas Coal Bed Methane (CBM)
Location Most natural gas is absorbed and trapped within nanopores in organic particles within shale formations and in the shale rock matrix Methane is absorbed in the solid matrix of the coal seam
Constituents Constituents of natural gas includes methane, ethane, butane, propane, gas condensate Coal seams contain negligible volumes of atomically heavier hydrocarbons such as butane and propane. No condensate present
Properties Intrinsic properties of shale including organic richness, maturity and clay mineral content determines how much gas may be in-place and possibly recovered Intrinsic properties of the coal seam determine how much gas can be recovered
Thickness Shale formations often hundreds of feet thick Thickness of seam not necessarily proportional to volume of gas produced (1-2 feet in Cherokee Basin in Kansas can be prolific, for example)
Porosity Shale often has significant porosity as high as 5 – 10 per cent. but low permeability which may require hydraulic fracturing) Very low porosity of coal seams (0.1 per cent. – 10 per cent.)
Production lifecycle Initial production often high before declining rapidly to produce at stable low levels Production increases during early de-watering stage and declines as water is pumped off and gas desorbs from coal
Investment lifecycle Ongoing continuous investment like a mining operation but rapid payback on wells if high commercial flow rates are achieved Large initial investment and more steady returns over time
Scale Single shale formations can be continental in scale with vast multi-TCF potential CBM often a local solution with multi-BCF resource potential