Investigating Dispersive H2 and CO2 Transport by means of medicalCT and GC-Supported Core Flooding Experiments

This study aims to quantify diffusion and dispersion effects that are important for reactivetransport processes and the efficiency of geological hydrogen storage. The focus is on hydrogen storage andhydrogen methanation in formations such as depleted natural gas reservoirs and aquifers. The interactionsbetween the initially equilibrated subsurface system and the injected gases, such as hydrogen or carbondioxide, are studied experimentally at the macroscopic level using computed tomography-based coreflooding. The experiments were carried out in a core flooding facility specially developed to characterisereactive transport processes in porous rock samples under reservoir conditions. Phenomena such asmolecular diffusion, dispersion, solubility in the remaining aqueous phase and biochemical reactionsinfluence the purity of the injected components and lead to concentration gradients in reservoirs andgeological storage sites. The spatial distribution of fluids and their effect on transport processes has a stronginfluence on the loss of recoverable hydrogen, as well as on microbial metabolism and, thus, on the growthof biomass in the pore space. This work includes gas-gas dispersion experiments in dry sandstone coresamples to quantify diffusive and dispersive effects during gas-gas displacement. Furthermore, comparableexperiments were carried out in water-saturated cores to determine the influence of the brine phase usuallypresent in reservoirs and its interaction with the injected gaseous components. The combined data fromchemical in-line analysis (gas chromatography) of the effluent gas, in-situ saturation measurements usingcomputed tomography, density and differential pressure measurements will ultimately be used to calibratereactive transport models that can also be upscaled to the field scale. As a future follow-up to this work, coreflooding experiments are planned with core samples that have been incubated with methanogenicmicroorganisms.