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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.


Related in: MedlinePlus

2-D cross sections of 3-D gray-scale images for the six carbonate rock samples studied: (a) Indiana limestone, (b) Estaillades limestone, (c) ME1, (d) ME2, (e) Ketton limestone, and (f) Mount Gambier limestone. The images were acquired with a SYRMEP beamline at the ELETTRA Synchrotron in Trieste, Italy.
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fig01: 2-D cross sections of 3-D gray-scale images for the six carbonate rock samples studied: (a) Indiana limestone, (b) Estaillades limestone, (c) ME1, (d) ME2, (e) Ketton limestone, and (f) Mount Gambier limestone. The images were acquired with a SYRMEP beamline at the ELETTRA Synchrotron in Trieste, Italy.

Mentions: [13] For transport studies we use four quarry carbonate samples (Indiana, Estaillades, Ketton, and Mount Gambier limestones) and two carbonate samples from a Middle East aquifer (denoted Middle Eastern carbonate 1 (ME1) and Middle Eastern carbonate 2 (ME2)). The dry scan images were acquired on cylindrical cores having 5 mm diameter and 25 mm length with a synchrotron beamline (Synchrotron Radiation MEdical Physics (SYRMEP) beamline at the ELETTRA Synchrotron in Trieste, Italy) at a resolution of 7.7 µm (for Indiana, Estaillades, Ketton, ME1, and ME2) and 9 µm (for Mount Gambier), corresponding to two different detector pixel sizes of 3.85 µm and 4.5 µm; the charge coupled device (CCD) camera binned the results giving the final voxel size of twice the detector pixel size. The range of energy used was 27–33 keV, and each scan lasted between 3 and 4 h. Reconstruction was performed by in-house software, resulting in images of around 6003 voxels from which a central cubic section was taken for our simulations. The 2-D cross sections of 3-D gray-scale images for the six carbonates studied are shown in Figures 1a–1f. Segmentation into binary images was based on a histogram analysis employing Otsu’s thresholding algorithm and using ImageJ software [Sahoo et al., 1988]. In addition, we acquired an additional image at a higher resolution, 3.3 µm voxel size, for Estaillades using a micro-CT scanner (Xradia Versa).


Insights into non-Fickian solute transport in carbonates.

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

2-D cross sections of 3-D gray-scale images for the six carbonate rock samples studied: (a) Indiana limestone, (b) Estaillades limestone, (c) ME1, (d) ME2, (e) Ketton limestone, and (f) Mount Gambier limestone. The images were acquired with a SYRMEP beamline at the ELETTRA Synchrotron in Trieste, Italy.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig01: 2-D cross sections of 3-D gray-scale images for the six carbonate rock samples studied: (a) Indiana limestone, (b) Estaillades limestone, (c) ME1, (d) ME2, (e) Ketton limestone, and (f) Mount Gambier limestone. The images were acquired with a SYRMEP beamline at the ELETTRA Synchrotron in Trieste, Italy.
Mentions: [13] For transport studies we use four quarry carbonate samples (Indiana, Estaillades, Ketton, and Mount Gambier limestones) and two carbonate samples from a Middle East aquifer (denoted Middle Eastern carbonate 1 (ME1) and Middle Eastern carbonate 2 (ME2)). The dry scan images were acquired on cylindrical cores having 5 mm diameter and 25 mm length with a synchrotron beamline (Synchrotron Radiation MEdical Physics (SYRMEP) beamline at the ELETTRA Synchrotron in Trieste, Italy) at a resolution of 7.7 µm (for Indiana, Estaillades, Ketton, ME1, and ME2) and 9 µm (for Mount Gambier), corresponding to two different detector pixel sizes of 3.85 µm and 4.5 µm; the charge coupled device (CCD) camera binned the results giving the final voxel size of twice the detector pixel size. The range of energy used was 27–33 keV, and each scan lasted between 3 and 4 h. Reconstruction was performed by in-house software, resulting in images of around 6003 voxels from which a central cubic section was taken for our simulations. The 2-D cross sections of 3-D gray-scale images for the six carbonates studied are shown in Figures 1a–1f. Segmentation into binary images was based on a histogram analysis employing Otsu’s thresholding algorithm and using ImageJ software [Sahoo et al., 1988]. In addition, we acquired an additional image at a higher resolution, 3.3 µm voxel size, for Estaillades using a micro-CT scanner (Xradia Versa).

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.


Related in: MedlinePlus