Visualization experiment for characterizing the influence of an open fracture on CO2 behavior in fractured porous media

While gas behavior influenced by the intricate interplay between fractures and the surrounding porous media can create complex flow paths and distribution, there is a scarcity of experimental research focusing on the influence of a fracture on gas behavior due to the limitation of implementing an open structure within porous media. In this study, we have implemented transparent porous structures embedding an open fracture in porous media by using a 3D printer. The study encompasses a series of experiments to visualize and quantify the spatiotemporal distribution of gaseous and dissolved CO₂ concentration by high-resolution pixel-wise image analysis. Results show that the presence of an open fracture significantly influences the behavior of CO₂, affecting both the migration and distribution of gas and dissolved CO₂ concentration. In addition, capillary fingering can be the trigger of early breaching across the fracture into the upper matrix which can create a highly discontinuous and heterogeneous spatiotemporal CO₂ distribution. The implications of this research are not limited to CO₂ behavior but extend to other gases and immiscible contaminants such as non-aqueous phase liquid whose behavior is different from that of groundwater. Our results suggest the applicability of the 3D printing technique in visualization experiments and the importance of incorporating detailed geological structures into environmental monitoring and predictive models for an effective environmental management.