Biogenic methane generation in the degradation of eastern Australian Permian coals

Hydrocarbons extracted from one Sydney Basin coal have a distribution of aromatic and aliphatic hydrocarbons consistent with a high degree of biodegradation as previously demonstrated for Bowen Basin coals. On the same basis, hydrocarbons from two other coals from the Sydney Basin are less biodegraded and display an additional minor series of alkylaromatic degradation products. All these degradation reactions generate CO2 which on biogenic reduction to CH4 is reservoired in association with the Permian coal-seams of the Sydney and Bowen Basins, Australia. Variations in access to oxygenated waters, nutrients and micro-organisms are held to be largely responsible for the extent of biodegradation of coal hydrocarbons and for the reduction of CO2.