Coalbed methane (CBM) is the naturally occurring methane-rich gas in coal seams, but its nomenclature is somewhat confusing in Australia. Coalbed methane is commonly known as coal seam gas (CSG) in Queensland and as coal seam methane (CSM) in New South Wales, South Australia and Western Australia. The coalbed methane that is associated with coalmining operations is traditionally called coalmine methane (CMM). The coalmine methane that is emitted to the atmosphere through mine ventilation systems is called ventilation air methane (VAM).
Table 1 contains a statistical summary of wells drilled for stand-alone coalbed methane exploration or development but does not list coalmine methane drainage wells. A total of 229 wells were drilled in 2005, but drilling activity was lower in 2005 than in 2004. This lower activity is primarily attributable to the fact that fewer development wells were drilled for the Moranbah project in the Bowen Basin in Queensland. However, this decline was partially offset by an increase in the number of development wells drilled in the Surat Basin in Queensland.
A notable increase in exploration drilling activities was achieved in the Clarence-Moreton, Nagoorin and Styx basins in the coastal regions of Queensland and in the Perth Basin in Western Australia in 2005. Not all these basins have been extensively explored for conventional petroleum.
A list of the operators of coalbed methane wells in Table 2 shows a gradual decrease in the number of operators despite the fact that overall drilling activities were much higher than several years before. Only five operators drilled more than 10 wells in 2005. This trend is a result of mergers and acquisitions. CH4 Gas (now a part of Arrow Energy) was the operator that drilled the most coalbed methane wells in 2003, 2004 and 2005.
Table.3 is a summary of coalbed methane production, which includes coalmine methane utilisation. Annual production growth in Queensland is remarkable, and this trend is likely to be maintained for a few more years.
Production commenced at the Spring Gully field in the Bowen Basin in 2005: this is the only new project commissioned during the year. This field adjoins the Fairview field, and the combined reserves of these two fields represent half of Australia's entire coalbed methane reserves.
Table 4 contains information on existing and future coalbed methane production and coalmine methane utilisation projects. The proven plus probable (2P) reserves on the table may be called ultimate recoveries in a strict sense, as no production adjustments have been made on the figures. In reality, however, frequent upward revisions of the reserves are more significant than the volumes of cumulative production.
As of September 2005, Australia's total 2P reserves of coalbed methane reached 3,477 PJ. This total amount is comparable roughly to those of an offshore conventional gas field to be developed for an LNG project in Australia.