Effect of tomography resolution on the calculated microscopic properties of porous materials: Comparison of sandstone and carbonate rocks

Gooya, R.; Bruns, Stefan; Müter, Dirk; Moaddel, A.; Harti, Ralph P.; Stipp, S. L. S.; Sørensen, Henning Osholm

doi:10.1063/1.4962389

Cited by 27 publications

(13 citation statements)

References 16 publications

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“…However, it has been shown that the spatial resolution of the 3D reconstruction has to be much finer than the morphological feature size to ensure that possible effects of medium structure on the transport characteristics are adequately captured. 37 Only in a few studies, information on the void space, obtained by physical reconstruction of porous materials with sufficiently fine resolution, was used to investigate numerically the diffusion of finite-size tracer particles. Langford et al 15 employed Brownian dynamics simulations to model diffusion of spherical probes of different sizes (varying from 0 up to 70 nm) in chromatographic adsorbents physically reconstructed using electron tomography with a resolution of about 3 × 3 × 5 nm.…”

Section: ■ Introductionmentioning

confidence: 99%

Tracer-Size-Dependent Pore Space Accessibility and Long-Time Diffusion Coefficient in Amorphous, Mesoporous Silica

2017

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Heterogeneous porous materials are widely used as fixed beds in adsorption, separation, and catalysis. An important aspect of mass transport in these materials is the hindrance to diffusion of molecules with dimensions approaching the pore size. We numerically study hindered diffusion of finite-size, passive (i.e., nonadsorbing, nonreacting) tracer particles in physically reconstructed amorphous, mesoporous silica from a hierarchical, macroporous–mesoporous silica monolith. The long-time, effective diffusion coefficient D eff is determined as a function of λ, the ratio of the tracer diameter to the average size of the mesopores. Results demonstrate a strong reduction of D eff with increasing tracer size. Comparison with theoretical models of hindered diffusion in a single uniform, cylindrical pore reveals that these models significantly overestimate D eff for λ > 0.2. Morphological analysis of the mesopore pore space accessible for finite-size tracers shows that its effective geometrical and topological properties are a function of λ. The nonuniform distribution of mesopore size results in an increased fraction of pores that become impermeable for larger tracers. As a consequence, not only is the accessible mesopore space (porosity) reduced for larger values of λ but also the connectivity of the accessible pore network decreases. Thus, in contrast to a single uniform pore, an increase of tracer size leads to two complementary effects in a heterogeneous porous medium: a constriction of the accessible pore space in individual pores and a reduction of the number of available diffusion paths in the pore network.

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Section: ■ Introductionmentioning

confidence: 99%

Tracer-Size-Dependent Pore Space Accessibility and Long-Time Diffusion Coefficient in Amorphous, Mesoporous Silica

2017

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“…This indicated that the sample was quite homogeneous and that the sampling volume we selected was a good representation of the material. The pore analysis of the sample 32 indicated that the pore radii within the volume ranged between 0.2 μ m and 1.0 μ m and the average pore radius was 0.4 μ m. The calculated absolute permeability for the volume, determined using the method described by Gooya et al . 32 , was 9.06 mD, which is within the range expected for chalk 33 .…”

Section: Resultsmentioning

confidence: 99%

“…The pore analysis of the sample 32 indicated that the pore radii within the volume ranged between 0.2 μ m and 1.0 μ m and the average pore radius was 0.4 μ m. The calculated absolute permeability for the volume, determined using the method described by Gooya et al . 32 , was 9.06 mD, which is within the range expected for chalk 33 . Because of the sample’s demonstrated homogeneity and because of computational limitations, we chose to use a 100 3 voxel volume, i.e.…”

Section: Resultsmentioning

confidence: 99%

Unstable, Super Critical CO2–Water Displacement in Fine Grained Porous Media under Geologic Carbon Sequestration Conditions

Gooya

Silvestri

Moaddel

et al. 2019

Sci Rep

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In this study we investigated fluid displacement water with supercritical (sc) CO 2 in chalk under conditions close to those used for geologic CO 2 sequestration (GCS), to answer two main questions: How much volume is available for scCO 2 injection? And what is the main mechanism of displacement over a range of temperatures? Characterization of immiscible scCO 2 displacement, at the pore scale in the complex microstructure in chalk reservoirs, offers a pathway to better understand the macroscopic processes at the continuum scale. Fluid behavior was simulated by solving the Navier-Stokes equations, using finite-volume methods within a pore network. The pore network was extracted from a high resolution 3D image of chalk, obtained using X-ray nanotomography. Viscous fingering dominates scCO 2 infiltration and pores remain only partially saturated. The unstable front, developed with high capillary number, causes filling of pores aligned with the flow direction, reaching a maximum of 70% scCO 2 saturation. The saturation rate increases with temperature but the final saturation state is the same for all investigated temperatures. The higher the saturation rate, the higher the dynamic capillary pressure coefficient. A higher dynamic capillary pressure coefficient indicates that scCO 2 needs more time to reach capillary equilibrium in the porous medium.

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“…We have previously analysed the effect of imaging resolution in two numerical contexts. We used a conventional CFD approach (finite volume method to solve the Stokes equation on binarised tomogram [ 48 ]) to show that the influence is rock type specific and is predominately reflected in the interconnectivity of pore spaces that require discretisation. We have also applied the reactor network model on tomographic data at three different resolutions [ 34 ].…”

Section: Discussionmentioning

confidence: 99%

Patterns of entropy production in dissolving natural porous media with flowing fluid

et al. 2018

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The tendency for irreversible processes to generate entropy is the ultimate driving force for structure evolution in nature. In engineering, entropy production is often used as an indicator for loss of usable energy. In this study, we show that the analysis of entropy production patterns can provide insight into the diverse observations from experiments that investigate porous medium dissolution in imposed flow field. We first present a numerical scheme for the analysis of entropy production in dissolving porous media. Our scheme uses a greyscale digital model for chalk (an extremely fine grained rock), that was obtained using X-ray nanotomography. Greyscale models preserve structural heterogeneities with very high fidelity. We focussed on the coupling between two types of entropy production: the percolative entropy, generated by dissipating the kinetic energy of fluid flow, and the reactive entropy, originating from the consumption of chemical free energy. Their temporal patterns pinpoint three stages of microstructural evolution. We then showed that local mixing deteriorates fluid channelisation by reducing local variations of reactant concentration. We also showed that microstructural evolution can be sensitive to the initial transport heterogeneities, when the macroscopic flowrate is low. This dependence on flowrate indicates the need to resolve the structural features of a porous system when fluid residence time is long.

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Effect of tomography resolution on the calculated microscopic properties of porous materials: Comparison of sandstone and carbonate rocks

Abstract: Effect of tomography resolution on the calculated microscopic properties of porous materials: comparison of sandstone and carbonate rocks.

Cited by 27 publications

References 16 publications

Tracer-Size-Dependent Pore Space Accessibility and Long-Time Diffusion Coefficient in Amorphous, Mesoporous Silica

Tracer-Size-Dependent Pore Space Accessibility and Long-Time Diffusion Coefficient in Amorphous, Mesoporous Silica

Unstable, Super Critical CO2–Water Displacement in Fine Grained Porous Media under Geologic Carbon Sequestration Conditions

Patterns of entropy production in dissolving natural porous media with flowing fluid

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