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Insights into non-Fickian solute transport in carbonates.

Bijeljic B, Mostaghimi P, Blunt MJ - Water Resour Res (2013)

Bottom Line: Mostaghimi, and M.Blunt (2013), Insights into non-Fickian solute transport in carbonates, Water Resour.Res., 49, 2714-2728, doi:10.1002/wrcr.20238.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Science and Engineering, Imperial College London London, UK.

ABSTRACT
[1] We study and explain the origin of early breakthrough and long tailing plume behavior by simulating solute transport through 3-D X-ray images of six different carbonate rock samples, representing geological media with a high degree of pore-scale complexity. A Stokes solver is employed to compute the flow field, and the particles are then transported along streamlines to represent advection, while the random walk method is used to model diffusion. We compute the propagators (concentration versus displacement) for a range of Peclet numbers (Pe) and relate it to the velocity distribution obtained directly on the images. There is a very wide distribution of velocity that quantifies the impact of pore structure on transport. In samples with a relatively narrow spread of velocities, transport is characterized by a small immobile concentration peak, representing essentially stagnant portions of the pore space, and a dominant secondary peak of mobile solute moving at approximately the average flow speed. On the other hand, in carbonates with a wider velocity distribution, there is a significant immobile peak concentration and an elongated tail of moving fluid. An increase in Pe, decreasing the relative impact of diffusion, leads to the faster formation of secondary mobile peak(s). This behavior indicates highly anomalous transport. The implications for modeling field-scale transport are discussed. Citation: Bijeljic, B., P. Mostaghimi, and M. J. Blunt (2013), Insights into non-Fickian solute transport in carbonates, Water Resour. Res., 49, 2714-2728, doi:10.1002/wrcr.20238.

No MeSH data available.


Estaillades limestone image: (a) the geometry shown as the pore volume represented by gray color; (b) normalized pressure field with a unit pressure difference across the model; (c) normalized flow field, where the ratios of the magnitude of u at the voxel centers divided by the average flow speed uav are shown using cones that are colored using a logarithmic scale spanning from 5 to 500. The same figures are shown for the Mount Gambier limestone image, denoted as (d), (e), and (f), respectively.
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fig03: Estaillades limestone image: (a) the geometry shown as the pore volume represented by gray color; (b) normalized pressure field with a unit pressure difference across the model; (c) normalized flow field, where the ratios of the magnitude of u at the voxel centers divided by the average flow speed uav are shown using cones that are colored using a logarithmic scale spanning from 5 to 500. The same figures are shown for the Mount Gambier limestone image, denoted as (d), (e), and (f), respectively.

Mentions: [22] An illustration of how flow is computed on the synchrotron images of Estaillades limestone (that is an exemplar for a carbonate with a wide spread of velocities) and Mount Gambier limestone (that is an exemplar for a carbonate with a narrower spread of velocities) is presented in Figures 3a–3f. The pore geometry, pressure field, and velocity field are shown. The velocity field figures show a subset of pore voxels where advection is dominant in comparison to diffusion: the stagnant flow voxels are not represented in Figure 3.


Insights into non-Fickian solute transport in carbonates.

Bijeljic B, Mostaghimi P, Blunt MJ - Water Resour Res (2013)

Estaillades limestone image: (a) the geometry shown as the pore volume represented by gray color; (b) normalized pressure field with a unit pressure difference across the model; (c) normalized flow field, where the ratios of the magnitude of u at the voxel centers divided by the average flow speed uav are shown using cones that are colored using a logarithmic scale spanning from 5 to 500. The same figures are shown for the Mount Gambier limestone image, denoted as (d), (e), and (f), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3814002&req=5

fig03: Estaillades limestone image: (a) the geometry shown as the pore volume represented by gray color; (b) normalized pressure field with a unit pressure difference across the model; (c) normalized flow field, where the ratios of the magnitude of u at the voxel centers divided by the average flow speed uav are shown using cones that are colored using a logarithmic scale spanning from 5 to 500. The same figures are shown for the Mount Gambier limestone image, denoted as (d), (e), and (f), respectively.
Mentions: [22] An illustration of how flow is computed on the synchrotron images of Estaillades limestone (that is an exemplar for a carbonate with a wide spread of velocities) and Mount Gambier limestone (that is an exemplar for a carbonate with a narrower spread of velocities) is presented in Figures 3a–3f. The pore geometry, pressure field, and velocity field are shown. The velocity field figures show a subset of pore voxels where advection is dominant in comparison to diffusion: the stagnant flow voxels are not represented in Figure 3.

Bottom Line: Mostaghimi, and M.Blunt (2013), Insights into non-Fickian solute transport in carbonates, Water Resour.Res., 49, 2714-2728, doi:10.1002/wrcr.20238.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Science and Engineering, Imperial College London London, UK.

ABSTRACT
[1] We study and explain the origin of early breakthrough and long tailing plume behavior by simulating solute transport through 3-D X-ray images of six different carbonate rock samples, representing geological media with a high degree of pore-scale complexity. A Stokes solver is employed to compute the flow field, and the particles are then transported along streamlines to represent advection, while the random walk method is used to model diffusion. We compute the propagators (concentration versus displacement) for a range of Peclet numbers (Pe) and relate it to the velocity distribution obtained directly on the images. There is a very wide distribution of velocity that quantifies the impact of pore structure on transport. In samples with a relatively narrow spread of velocities, transport is characterized by a small immobile concentration peak, representing essentially stagnant portions of the pore space, and a dominant secondary peak of mobile solute moving at approximately the average flow speed. On the other hand, in carbonates with a wider velocity distribution, there is a significant immobile peak concentration and an elongated tail of moving fluid. An increase in Pe, decreasing the relative impact of diffusion, leads to the faster formation of secondary mobile peak(s). This behavior indicates highly anomalous transport. The implications for modeling field-scale transport are discussed. Citation: Bijeljic, B., P. Mostaghimi, and M. J. Blunt (2013), Insights into non-Fickian solute transport in carbonates, Water Resour. Res., 49, 2714-2728, doi:10.1002/wrcr.20238.

No MeSH data available.