This study presents experimental adsorption–desorption data of CH4 and CO2 on shale samples from the Cesar-Ranchería Basin, Colombia, a region with limited characterization of gas–rock interactions under reservoir-relevant conditions. The work addresses the behavior of early-mature shales, contributing to the understanding of gas retention mechanisms in tropical basins. Adsorption–desorption isotherms were obtained using a high-pressure manometric system at 50 °C and 80 °C, with pressures up to 3 MPa, and were fitted using the Langmuir model. The results show a consistently higher adsorption capacity for CO2 compared to CH4 across all conditions, along with a clear decrease in adsorption capacity with increasing temperature, confirming the exothermic nature of the process. No hysteresis was observed, indicating fully reversible adsorption dominated by physisorption mechanisms. The integration of adsorption data with mineralogical, BET surface area, and geochemical characterization provides insight into the factors controlling gas retention in early-mature shales. The results highlight the combined influence of surface area, organic matter, and clay mineralogy on adsorption performance, and demonstrate that CO2 exhibits a stronger affinity for the shale matrix under all tested conditions. These findings contribute experimental evidence of gas adsorption behavior in an underexplored basin and provide a reference framework for evaluating gas storage potential in similar geological settings.
Cancino et al. (Mon,) studied this question.