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Transport processes in porous media have been traditionally studied through the parameterization of macroscale properties, by means of volume-averaging or upscaling methods over a representative elementary volume. The possibility of upscaling results from pore-scale simulations, to obtain volume-averaging properties useful for practical purpose, can enhance the understanding of transport effects that manifest at larger scales. Several studies have been carried out to investigate the impact of the geometric properties of porous media on transport processes for solute species. However, the range of pore-scale geometric properties, which can be investigated, is usually limited to the number of samples acquired from microcomputed tomography images of real porous media. The present study takes advantage of synthetic porous medium generation to propose a systematic analysis of the relationships between geometric features of the porous media and transport processes through direct simulations of fluid flow and advection-diffusion of a non-reactive solute. Numerical simulations are performed with the lattice Boltzmann method on synthetic media generated with a geostatistically based approach. Our findings suggest that the advective transport is primarily affected by the specific surface area and the mean curvature of the porous medium, while the effective diffusion coefficient scales as the inverse of the tortuosity squared. Finally, the possibility of estimating the hydrodynamic dispersion coefficient knowing only the geometric properties of porous media and the applied pressure gradient has been tested, within the range of tested porous media, against advection-diffusion simulations at low Reynolds (, Geofluids, 11 (6), ISSN:1468-8115, ISSN:1468-8123

Biochar was tested as an active capping material for oil spill contaminated sediment and its performance was compared to activated carbon and organoclay. Polydimethyilsiloxane fibers were used as passive samplers to evaluate the vertical porewater concentration of selected polycyclic aromatic hydrocarbons through the sea-sediment and the capping layer (1 cm resolution). Experiments were carried out on the laboratory scale using 7.5 cm (∼500 g) of contaminated sea-sediment that were capped with 3 cm (∼150 g) of capping materials. The porewater concentrations of the polycyclic aromatic hydrocarbons were compared using a reactive-diffusion model. Biochar showed a greater capping efficiency than activated carbon and organoclay. For example, anthracene porewater concentrations in the first centimetre of capping material, after 1 month, were reduced by 69%, 56% and 99% respectively for activated carbon, organoclay and biochar. The porewater concentrations were used to model the long term (≥12 months) behaviour of various cap configurations with a numerical simulations. Biochar can be considered a cost-effective alternative to the more consolidated sorbent materials.

Phase separation of formation fluids in the subsurface introduces hydrodynamic perturbations which are critical for mass and energy transport of geofluids. Here, we present pore-scale lattice-Boltzmann simulations to investigate the hydrodynamical response of a porous system to the emergence of non-wetting droplets under background hydraulic gradients. A wide parameter space of capillary number and fluid saturation is explored to characterize the droplet evolution, the droplet size and shape distribution, and the capillary-clogging patterns. We find that clogging is favored by high capillary stress; nonetheless, clogging occurs at high non-wetting saturation (larger than 0.3), denoting the importance of convective transport on droplet growth and permeability. Moreover, droplets are more sheared at low capillary number; however, solid matrix plays a key role on droplet’s volume-to-surface ratio., Geofluids, 2019, ISSN:1468-8115, ISSN:1468-8123