The Effects of Injection and Production Well Arrangement on Carbon Dioxide Sequestration in Deep, Unmineable Coal Seams: A Numerical Study

Carbon dioxide (CO2) sequestration in deep, unmineable coal seams provides a promising opportunity for the reduction of anthropogenic greenhouse gas emissions. However, little is known about optimal design features of the required in-ground infrastructure. Here, we report on a numerical study investigating the influence of the number of injection (and production) wells and their arrangement on the CO2 storage capacity of a coal-seam reservoir. The results of the modelling reveal a decline in injection rates and practical storage capacities with continued CO2 injection. This is related to coal matrix swelling (and associated permeability decrease) caused by adsorption of injected CO2 on coal, coupled with increasing reservoir pore pressures during injection, which reduce the pressure gradient from well to reservoir and thus the impetus for flow. Modelling carried out for scenarios with multiple wells showed an increase in storage capacity for the two-well scenario but a reduction in storage capacity for th...