The Huntly coalfield has significant coal deposits that contain biogenically-sourced methane. The coals are subbituminous in rank and Eocene in age and have been previously characterised with relatively low to moderate measured gas (CH 4 ) contents (2–4 m 3 /ton). The CO 2 holding capacity is relatively high (18.0 m 3 /ton) compared with that of CH 4 (2.6 m 3 /ton) and N 2 (0.7 m 3 /ton) at the same pressure (4 MPa; all as received basis). The geothermal gradient is also quite high at 55 °C/km.A study has been conducted which simulates enhancement of methane recovery (ECBM) from these deposits using a new version of the TOUGH2 (version 2) reservoir simulator (ECBM-TOUGH2) that can handle non-isothermal, multi-phase flows of mixtures of water, CH 4 , CO 2 and N 2 . The initial phase of the simulation is CH 4 production for the first 5 years of the field history. The model indicates that methane production can be significantly improved (from less than 80% recovery to nearly 90%) through injection of CO 2 . However, although an increase in the rate of CO 2 injection increases the amount of CO 2 sequestered, the methane recovery (because of earlier breakthrough with increasing injection rate) decreases. Modeling of pure N 2 injection produced little enhanced CH 4 production. The injection of a hypothetical flue gas mixture (CO 2 and N 2 ) also produced little increase in CH 4 production. This is related to the low adsorption capacity of the Huntly coal to N 2 which results in almost instantaneous breakthrough into the production well.