Influence of Depth on CO2/CH4 Sorption Ratio in Deep Coal Seams

Abstract

The present work aims to analyse the influence of present-day burial depths of coal seams on the sorption properties towards CH4 and CO2, respectively. For medium-rank coals located in the southwestern area of the Upper Silesian Coal Basin (USCB), the gravimetric sorption measurements were carried out with pure gases at a temperature of 30 °C. The variability of CO2/CH4 exchange sorption and diffusivity ratios was determined. It was revealed that in coal seams located at a depth above 700 m, for which the sorption exchange ratio was the greatest, the process of CO2 injection for permanent storage was more beneficial. In the coal seams lying deeper than 700 m with a lower CO2/CH4 sorption ratio, the CH4 displacement induced by the injection of CO2 (CO2-ECBM recovery) became more favourable.