Evaluating the adsorbed gas content in shale gas reservoirs is crucial for calculating total gas production potential of the reservoir. In this study, we analyzed the chemical composition and total organic carbon content of the black shale samples collected from different depths in the Liard Basin, Canada. The samples were identified as siliceous-rich shale samples; specifically, organic-rich black shale with a TOC content of more than approximately 3%. We also analyzed the adsorbed methane gas content and the pore structure of the shale samples. We conducted a mechanistic study to identify the important factors affecting the amount of adsorbed CH₄ gas in the shale by evaluating the correlation between the adsorbed CH₄ gas content and quantitative pore structure results (i.e., specific surface area and micropore, mesopore, and macropore volume). The results indicate that the micropore volume can be effectively used to predict the content of adsorbed CH₄ gas in organic-rich black shale samples from the Liard Basin.