Coalbed Methane - Reserves

Reserves

Coalbed methane reserve estimates vary; however a 1997 estimate from the U.S. Geological Survey predicts more than 700 trillion cubic feet (20 trillion cubic metres) of methane within the US. At a natural gas price of US$6.05 per million Btu (US$5.73/GJ), that volume is worth US$4.37trillion. At least 100 trillion cubic feet (2.8 trillion cubic metres) of it is economically viable to produce.

In Canada, British Columbia is estimated to have approximately 90 trillion cubic feet (2.5 trillion cubic metres) of coalbed gas. Alberta, to date the only province with commercial coalbed methane wells, is estimated to have approximately 170 trillion cubic feet (4.8 trillion cubic metres) of economically recoverable coalbed methane.

Recent depressed natural gas prices have made CBM less economically viable compared to the past few years.

Currently it is considered a non-renewable resource, there is evidence by the Alberta Research Council, Alberta Geological Survey and others showing coalbed methane is a renewable resource, because the bacterial action that formed the methane is ongoing. The assertion of being renewable, however, has itself become one of debate since it has also been shown that the dewatering that accompanies CBM production destroys the conditions needed for the bacteria to produce methane. In addition, the rate of formation of additional methane is undetermined. This debate is currently causing a right of ownership issue in the Canadian province of Alberta, as only non-renewable resources can legally be owned by the province.

Production forecasting of CBM wells and fields can be performed using specialised Material Balance tools or Numerical simulators, as it requires an explicit coupling of the matrix gas diffusion process with the flow within fractures (Darcy law applies).