The injection of carbon dioxide (CO2) and/or nitrogen (N2) in deep, unmineable coalbeds can enhance the recovery of coalbed methane (CBM). If CO2, a greenhouse gas (GHG), is injected, it is also a very attractive option for geologic storage of GHG, as CO2 is strongly adsorbed onto the coal.

Existing CBM numerical simulators have been developed to model the primary CBM recovery process. However, mechanisms in the enhanced CBM processes are more complex. Therefore, improvements on the simulators are needed to consider the additional features such as: (1) stress related permeability alteration during gas injection/production; (2) coal swelling/shrinkage due to gas adsorption/desorption on coal; (3) mixed gas adsorption; (4) mixed gas diffusion; and (5) non-isothermal effect for gas injection.

This presentation describes an overview of the new developments on the existing CBM simulators (e.g., CMG's GEM, CSIRO/TNO's SIMED II and ARI's COMET3) to meet the challenges of modelling the enhanced CBM recovery processes. An ongoing CBM simulator comparison study funded by the National Energy Technology Laboratory (NETL) of the U.S. Department of Energy (DOE) in the GEO-SEQ Project led by the Lawrence Berkeley National Laboratory (LBNL) is providing an opportunity for the software developers to test the new features in their simulators.