Quantitative Analysis of Flow Processes in a Sand Using Synchrotron-Based X-ray Microtomography

Wildenschild, D.; Hopmans, Jan W.; Rivers, Mark L.; Kent, Adam J.R.

doi:10.2113/4.1.112

Cited by 127 publications

(94 citation statements)

References 35 publications

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“…[5] X-ray computed microtomography (X-CMT) performed at a synchrotron research center provides the ability to obtain three-dimensional, in situ observations of the internal structure of materials with micron-scale resolution [Auzerais et al, 1996;Flannery et al, 1987;Li et al, 2006;Spanne et al, 1994;Wildenschild et al, 2005]. The distributions of individual elements can be determined by performing difference tomography, where the X-rays used to image the sample are selected to be just below and above the absorption edge of the element of interest.…”

Section: X-ray Difference Microtomographymentioning

confidence: 99%

Imaging of colloidal deposits in granular porous media by X‐ray difference micro‐tomography

Gaillard

Chen

Stonedahl

et al. 2007

Geophysical Research Letters

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[1] High resolution synchrotron-based X-ray computed microtomography (X-CMT) was used to identify the morphology of colloidal deposits formed in porous media. We show that difference microtomography -whereby a tomographic reconstruction is performed across an absorption edge -provides valuable information on the nature and location of the aggregates formed by the deposition of colloidal particles. Column experiments were performed using an idealized porous medium consisting of glass beads through which colloidal ZrO 2 particles were transported. Tomographic reconstructions of the porous medium and of the aggregate structure provide an unique opportunity to observe colloidal particle deposits and of their morphology. These results show that the local pore geometry controls particle deposition and that deposits tend to form in a rather heterogeneous manner in the porous medium.

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Section: X-ray Difference Microtomographymentioning

confidence: 99%

Imaging of colloidal deposits in granular porous media by X‐ray difference micro‐tomography

Gaillard

Chen

Stonedahl

et al. 2007

Geophysical Research Letters

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“…X-ray micro-computed tomography (µ-CT) multiphase flow experiments are aimed at imaging the in situ fluid phase distributions in porous media (Wildenschild et al 2005;Silin et al 2010;Iglauer et al 2011;Setiavan et al 2012;Andrew et al 2014). Recently, fast synchrotron-based µ-CT has been used to image fluid distributions under dynamic conditions (Berg et al 2013b); the term "dynamic" means that fluid flow is maintained while imaging, with ms integration times thus enabling dynamic process studies on basis of a series of images.…”

Section: Introductionmentioning

confidence: 99%

Fast X-ray Micro-Tomography of Multiphase Flow in Berea Sandstone: A Sensitivity Study on Image Processing

et al. 2014

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Synchrotron-based fast micro-tomography is the method of choice to observe in situ multiphase flow and displacement dynamics on the pore scale. However, the image processing workflow is sensitive to a suite of manually selected parameters which can lead to ambiguous results. In this work, the relationship between porosity and permeability in response to systematically varied gray-scale threshold values was studied for different segmentation approaches on a dataset of Berea sandstone at a voxel length of 3 µm. For validation of the image processing workflow, porosity, permeability, and capillary pressure were compared to laboratory measurements on a larger-sized core plug of the same material. It was found that for global thresholding, minor variations in the visually permissive range lead to large variations in porosity and even larger variations in permeability. The latter is caused by changes in the pore-scale flow paths. Pore throats were found to be open for flow at large thresholds but closed for smaller thresholds. Watershed-based segmentation was found to be significantly more robust to manually chosen input parameters. Permeability and capillary pressure closely match experimental values; for capillary pressure measurements, the plateau of calculated capillary pressure curves was similar to experimental curves. Modeling on structures segmented with hysteresis thresholding was found to overpredict experimental capillary pressure values, while calculated permeability showed reasonable agreement to experimental data. This demonstrates that a good representation of permeability or capillary pressure alone is not a sufficient quality criterion for appropriate segmentation, but the data should be validated with both parameters. However, porosity is the least reliable quality criterion. In the segmented images, always a lower porosity was found compared to experimental values due to micro-porosity below the imaging resolution. As a result, it is recommended to base the validation of image processing workflows on permeability and capillary pressure and not on porosity. Decane-brine distributions from a multiphase flow experiment were modeled in a thus validated µ-CT pore space using a morphological approach which captures only capillary forces. A good overall correspondence was found when comparing (capillary-controlled) equilibrium fluid distributions before and after pore-scale displacement events.

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“…The previously unidentified displacement mechanism has implications for (i) enhanced oil recovery, (ii) remediation of nonaqueous liquid contaminants in aquifers, and (iii) subsurface CO 2 storage. such as bead packs (22), sand packs (22)(23)(24)(25)(26), and sandstones (8,18,21,23), but less attention has been paid to carbonate rocks. However, more than 50% of the world's remaining oil reserves are located in carbonate reservoirs (27), and carbonate aquifers supply water wholly or partially to one quarter of the global population (28).…”

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confidence: 99%

Droplet fragmentation: 3D imaging of a previously unidentified pore-scale process during multiphase flow in porous media

Pak

Butler

Geiger

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

151

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Using X-ray computed microtomography, we have visualized and quantified the in situ structure of a trapped nonwetting phase (oil) in a highly heterogeneous carbonate rock after injecting a wetting phase (brine) at low and high capillary numbers. We imaged the process of capillary desaturation in 3D and demonstrated its impacts on the trapped nonwetting phase cluster size distribution. We have identified a previously unidentified pore-scale event during capillary desaturation. This pore-scale event, described as droplet fragmentation of the nonwetting phase, occurs in larger pores. It increases volumetric production of the nonwetting phase after capillary trapping and enlarges the fluid−fluid interface, which can enhance mass transfer between the phases. Droplet fragmentation therefore has implications for a range of multiphase flow processes in natural and engineered porous media with complex heterogeneous pore spaces.droplet fragmentation | X-ray computed microtomography | pore-scale imaging | heterogeneous porous media | carbonate rock M ultiphase fluid displacement processes in porous media are important for a broad range of natural and engineering applications such as transport of nonaqueous phase liquid contaminants in aquifers, oil and gas production from hydrocarbon reservoirs, subsurface CO 2 storage, or gas transport in fuel cells. Herein, capillary trapping is a fundamental mechanism that causes immobilization of a portion of the resident nonwetting phase when it is displaced by an invading wetting phase. As a result, production of the nonwetting phase is always less than 100%.The pore-scale physics of capillary trapping are broadly understood, as the underlying mechanisms such as piston-like displacement, snap-off and film development have been observed in physical micromodel experiments and quantitative theories have been established for them (1-4). The conventional view considers such pore-scale processes to occur between multiple pores, i.e., they are interpore processes and the pores are defined as volumes connected by narrower pore throats. By contrast, intrapore processes, as presented in this paper, are not well established in the literature. During drainage (i.e., where a nonwetting phase displaces the wetting phase), the wetting phase can establish films in the corners of the pores, which results in its continuous production and hence low residual saturations of the wetting phase. During imbibition (i.e., where the wetting phase displaces a nonwetting phase), swelling of the corner wetting films causes snap-off of the nonwetting phase, which results in capillary trapping of the nonwetting phase. The trapped nonwetting phase exists as disconnected ganglia within the pore network. Numerical pore network models have been developed to include these porelevel mechanisms with the aim of predicting the macroscopic flow properties of porous materials such as the structure of the phase distributions, residual saturation, relative permeability functions, and capillary pressure curves. Some of these mod...

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Quantitative Analysis of Flow Processes in a Sand Using Synchrotron-Based X-ray Microtomography

Cited by 127 publications

References 35 publications

Imaging of colloidal deposits in granular porous media by X‐ray difference micro‐tomography

Imaging of colloidal deposits in granular porous media by X‐ray difference micro‐tomography

Fast X-ray Micro-Tomography of Multiphase Flow in Berea Sandstone: A Sensitivity Study on Image Processing

Droplet fragmentation: 3D imaging of a previously unidentified pore-scale process during multiphase flow in porous media

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