Low-permeability, dual-porosity media such as coal and gas shale (i.e., mudstone) exhibit structural and chemical features across a range of scales spanning from tens of meters to nanometers. Characterization methods and efforts for these porous media are needed to understand gas in place, gas flow behavior, and storage capacity for potential CO sequestration. Characterizing the structure and heterogeneity of representative samples helps determine how the physical and chemical processes associated with CO transport in coal and gas shale affect injectivity and storage capacity (over long periods of time), and the ability of these media to sequester CO (as both a free and adsorbed phase) for thousands of years. In this study, an imaging technique focused on the submillimeter scale is applied to shale and coal samples of interest. In particular, porosity, component matrix distribution, and evidence of gas transport through these tight media were studied.