A numerical simulation study of injecting CO2 into coal bed (enhanced coal bed methane) to reduce GHG emission

Abstract

Increasing concentrations of greenhouse gases (GHG), including CO2, will lead to changes in the Earth’s climate with the consequence of the rise in the global average temperature. Reducing CO2 atmospheric concentrations by capturing emissions at the source and then storing them in subsurface reservoirs is considered a reliable solution until emission-free energy sources are developed and viable. Depleted oil and gas reservoirs, saline water aquifer, un-mineable coals are common sites for underground storage. The injection of CO2 in coal beds, known as ECBM is considered one of the most efficient and favorable economic options of all storage because CO2 is stored and at the same time will improve the recovery of coal bed methane. This method has huge potential as Indonesia hosts many coal deposits, however, exploitation of CBM is still very limited and mostly on pilot project status. The objectives of this study are to realize the potential value of ECBM and understand important operating parameters that will optimize the project. Reservoir simulations are an inexpensive method for predicting optimal trade-offs between these two separated processes (maximum storage/sequestration and maximum CBM production). This study reveals that methane recovery dependent strongly on the injection rate, while coal swelling/shrinkage only affects early production.