Abstract: CO2 and CH4 Sorption Kinetics on Coal: Experiments and Potential Application in CBM/Ecbm Modeling (original) (raw)

Numerical modelling of the processes of CO 2 storage in coal seams and enhanced coalbed methane (ECBM) production requires information on the kinetics (rates) of the sorption/desorption processes. In order to address this issue which is of relevance in different EU-projects (ICBM, RECOPOL, Siemons et al. 2003), the sorption kinetics of CO 2 and methane were studied on a high volatile bituminous coal (VR r = 0.68 %) from the Upper Silesian Basin, Poland, in the dry and moisture-equilibrated state. The experiments were conducted on six different grain size fractions, ranging from <63 µm to >2000 µm at temperatures of 45°C and 32°C using a volumetric experimental setup. CO 2 sorption was consistently faster than methane sorption under all experimental conditions. Further qualitative results showed that moisture in the coal leads to a significant reduction in the sorption rates by a factor of >two and that the sorption rate is positively correlated with temperature. Generally, adsorption rates decreased with increasing grain size for all experimental conditions. Based on the experimental results simple modelling approaches are proposed for the sorption kinetics of carbon dioxide and methane that may be readily implemented into reservoir simulators. Evaluation of the fitting parameters resulted in a two phase process associated with the combined adsorption/diffusion process, one slow and one rapid process. These two processes have been compared in terms of a dependency of grain size.