scholarly journals Reliable estimation of hydraulic permeability from 3D X-ray CT images of porous rock

2020 ◽  
Vol 205 ◽  
pp. 08004
Author(s):  
Eomzi Yang ◽  
Dong Hun Kang ◽  
Tae Sup Yun
Keyword(s):  
Pore Structure ◽  
Structural Information ◽  
Pore Space ◽  
Finite Size ◽  
Image Resolution ◽  
Accurate Estimation ◽  
Hydraulic Permeability ◽  
Related Phenomenon ◽  
X Ray ◽  
Segmentation Methods

The hydraulic permeability is a key parameter for simulating the flow-related phenomenon so that its accurate estimation is crucial in both experimental and numerical simulation studies. 3D pore structure can be readily taken by X-ray computed tomography (CT) and it often serves as a flow domain for pore-scale simulation. However, one encounters the challenges in segmenting the authentic pore structure owing to the finite size of image resolution and segmentation methods. Therefore, the loss of structural information in pore space seems unavoidable to result in the unreliable estimation of permeability. In this study, we propose a novel framework to overcome these limitations by using a flexible ternary segmentation scheme. Given the pore size distribution curve and porosity, three phases of pore, solid, and gray regions are segmented by considering the partial volume effect which holds the composition information of unresolved objects. The resolved objects such as solid and pore phases are taken to equivalently solve Stokes equation while the fluid flow through unresolved objects is simultaneously solved by Stokes-Brinkmann equation. The proposed numerical scheme to obtain the permeability is applied to Indiana limestone and Navajo sandstone. The results show that the computed hydraulic permeability is similar to the experimentally obtained value without being affected by image resolution. This approach has advantages of achieving consistent permeability values, less influenced by segmentation methods.

scholarly journals An X-ray micro-tomographic study of the pore space, permeability and percolation threshold of young sea ice

2021 ◽  
Vol 15 (8) ◽  
pp. 4047-4072
Author(s):  
Sönke Maus ◽  
Martin Schneebeli ◽  
Andreas Wiegmann
Keyword(s):  
Sea Ice ◽  
Pore Space ◽  
Permeability Transition ◽  
Hydraulic Permeability ◽  
X Ray ◽  
Model Studies ◽  
Vertical Permeability ◽  
Porosity And Permeability ◽  
Brine Volume

Abstract. The hydraulic permeability of sea ice is an important property that influences the role of sea ice in the environment in many ways. As it is difficult to measure, so far not many observations exist, and the quality of deduced empirical relationships between porosity and permeability is unknown. The present work presents a study of the permeability of young sea ice based on the combination of brine extraction in a centrifuge, X-ray micro-tomographic imaging and direct numerical simulations. The approach is new for sea ice. It allows us to relate the permeability and percolation properties explicitly to characteristic properties of the sea ice pore space, in particular to pore size and connectivity metrics. For the young sea ice from the present field study we obtain a brine volume of 2 % to 3 % as a threshold for the vertical permeability (transition to impermeable sea ice). We are able to relate this transition to the necking of brine pores at a critical pore throat diameter of ≈0.07 mm, being consistent with some limited pore analysis from earlier studies. Our optimal estimate of critical brine porosity is half the value of 5 % proposed in earlier work and frequently adopted in sea ice model studies and applications. By placing our results in the broader context of earlier studies, we conclude that the present threshold is more significant in that our centrifuge experiments and high-resolution 3D image analysis enable us to more accurately identify the threshold below which fluid connectivity ceases by examining the brine inclusion microstructure on finer scales than were previously possible. We also find some evidence that the sea ice pore space should be described by directed rather than isotropic percolation. Our revised porosity threshold is valid for the permeability of young columnar sea ice dominated by primary pores. For older sea ice containing wider secondary brine channels, for granular sea ice and for the full-thickness bulk permeability, other thresholds may apply.

scholarly journals X-ray CT analysis of pore structure in sand

2016 ◽  
Author(s):  
Toshifumi Mukunoki ◽  
Yoshihisa Miyata ◽  
Kazuaki Mikami ◽  
Erika Shiota
Keyword(s):  
Image Analysis ◽  
Pore Structure ◽  
Pore Diameter ◽  
Pore Space ◽  
Soil Mechanics ◽  
Three Dimensional ◽  
Image Data ◽  
Petroleum Engineering ◽  
X Ray ◽  
Definition Of

Abstract. The development of a micro-focused X-ray CT device enables digital imaging analysis at the pore-scale. The applications have been diverse, for instance, in soil mechanics, geotechnical and geoenvironmental engineering, petroleum engineering, and agricultural engineering. In particular, imaging of the pore space of porous media has contributed to numerical simulations for single and multi-phase flow, or contaminant transport, through the pore structure as three-dimensional image data. These obtained results are affected by the pore diameter so it is necessary to verify the image pre-processing for image analysis, and validate the pore diameters obtained from the CT image data. Besides, it is meaningful to produce the parameters in a representative element volume (REV) and significant to define the dimension of REV. This paper describes the underlying method of image processing and analysis and discusses the physical properties of Toyoura sand for the verification of image analysis based on the definition of REV. Based on the obtained verification results, pore diameter analysis can be conducted and validated by the comparison of the experimental work and image analysis. The pore diameter was deduced by Laplace’s law and the water retentively test for the drainage process. The referenced result sand perforated pore diameter proposed originally in this study, called the voxel-percolation method (VPM), are compared in this paper. The paper describes the limitation of REV, the definition of pore diameter, and the effectiveness of VPM for the assessment of pore diameter.

scholarly journals X-ray CT analysis of pore structure in sand

Solid Earth ◽  
2016 ◽  
Vol 7 (3) ◽  
pp. 929-942 ◽  
Author(s):  
Toshifumi Mukunoki ◽  
Yoshihisa Miyata ◽  
Kazuaki Mikami ◽  
Erika Shiota
Keyword(s):  
Image Analysis ◽  
Pore Structure ◽  
Pore Diameter ◽  
Pore Space ◽  
Soil Mechanics ◽  
Image Data ◽  
Petroleum Engineering ◽  
Physical Parameters ◽  
X Ray ◽  
Definition Of

Abstract. The development of microfocused X-ray computed tomography (CT) devices enables digital imaging analysis at the pore scale. The applications of these devices are diverse in soil mechanics, geotechnical and geoenvironmental engineering, petroleum engineering, and agricultural engineering. In particular, the imaging of the pore space in porous media has contributed to numerical simulations for single-phase and multiphase flows or contaminant transport through the pore structure as three-dimensional image data. These obtained results are affected by the pore diameter; therefore, it is necessary to verify the image preprocessing for the image analysis and to validate the pore diameters obtained from the CT image data. Moreover, it is meaningful to produce the physical parameters in a representative element volume (REV) and significant to define the dimension of the REV. This paper describes the underlying method of image processing and analysis and discusses the physical properties of Toyoura sand for the verification of the image analysis based on the definition of the REV. On the basis of the obtained verification results, a pore-diameter analysis can be conducted and validated by a comparison with the experimental work and image analysis. The pore diameter is deduced from Young–Laplace's law and a water retention test for the drainage process. The results from previous study and perforated-pore diameter originally proposed in this study, called the voxel-percolation method (VPM), are compared in this paper. In addition, the limitations of the REV, the definition of the pore diameter, and the effectiveness of the VPM for an assessment of the pore diameter are discussed.

scholarly journals An X-ray micro-tomographic study of the pore space, permeability and percolation threshold of young sea ice

2020 ◽  
Author(s):  
Sönke Maus ◽  
Martin Schneebeli ◽  
Andreas Wiegmann
Keyword(s):  
Sea Ice ◽  
Pore Space ◽  
Permeability Transition ◽  
Hydraulic Permeability ◽  
X Ray ◽  
Model Studies ◽  
Vertical Permeability ◽  
Porosity And Permeability ◽  
Brine Volume

Abstract. The hydraulic permeability of sea ice is an important property that influences the role of sea ice in the environment in many ways. As it is difficult to measure, so far not many observations exist and the quality of deduced empirical relationships between porosity and permeability is unknown. The present work presents a study of the permeability of young sea ice based on the combination of X-ray tomographic imaging and direct numerical simulations. The approach is new for sea ice. It allows to relate the permeability and percolation properties explicitly to characteristic properties of the sea ice pore space, in particular to pore size and connectivity metrics. For the young ice from the present field study we obtain a brine volume of 2.4 ± 0.3 % as threshold for the vertical permeability (transition to impermeable sea ice). We are able to relate this transition to the necking of brine pores at a critical pore throat diameter of ≈ 0.07 mm, being consistent with some limited pore analysis from earlier studies. The obtained critical brine porosity is considerably smaller than the value of 5 % proposed in earlier work and frequently adopted in sea ice model studies and applications. We revise the uncertainties associated with earlier estimates suggesting that the present result is more accurate. We then propose a consistent parametrisation for the permeability of young sea ice that will be useful for modelling. The study highlights the large potential of X-ray tomography, in combination with appropriate sampling, storage and processing, to derive physical properties of sea ice.

Pore scale imaging and modelling of coal properties

2015 ◽  
Vol 55 (2) ◽  
pp. 468
Author(s):  
Hamed Lamei Ramandi ◽  
Peyman Mostaghimi ◽  
Ryan T. Armstrong ◽  
Christoph H. Arns ◽  
Mohammad Saadatfar ◽  
...  
Keyword(s):  
Large Scale ◽  
Pore Space ◽  
Image Resolution ◽  
X Ray ◽  
Flow Simulations ◽  
The Core ◽  
Sensitivity Studies ◽  
X Ray Computed ◽  
3D Image Registration ◽  
Stress Dependent

A key parameter in determining the productivity and commercial success of coal seam gas wells is the permeability of individual seams. Laboratory testing of core plugs is commonly used as an indicator of potential seam permeability. The highly heterogeneous and stress-dependent nature of coal makes laboratory measurements difficult to perform and the results difficult to interpret. Consequently, permeability in coal is poorly understood. The permeability of coal at the core scale depends on the geometry, topology, connectivity, mineralisation and spatial distribution of the cleat system, and a better understanding of coal permeability, that and the factors that control this depends on having a better understanding and detailed characterisation of the system. The authors used high resolution micro-focus X-ray computed tomography and 2D-3D image registration techniques to overlay tomograms of the same core plug, with and without X-ray attenuating fluids present in the pore space, with 2D scanning electron microscope images to produce detailed 3D visualisations of the geometry and topology of the cleat systems in the coal plugs. Novel filtering algorithms were used to produce segmentations that preserve cleat aperture dimensions and together with large-scale fluid flow simulations, they performed directly on the images and were used to compute porosities and permeabilities. Image resolution and segmentation sensitivity studies are also described, which show that the core scale permeability is controlled by a small number of well-connected percolating cleats. The results of this study demonstrate the potential of simple image-based analysis techniques to provide rapid estimates of core plug permeabilities.

Binarization of soil X-ray tomography images: revisiting Otsu’s method

2020 ◽  
Author(s):  
Konstantin Abrosimov ◽  
Konstantin Romanenko ◽  
Kirill Gerke
Keyword(s):  
Image Fusion ◽  
Vadose Zone ◽  
Pore Space ◽  
Three Dimensional ◽  
Hierarchical Structures ◽  
Individual Characteristics ◽  
Image Resolution ◽  
Gray Scale ◽  
X Ray ◽  
Local Methods

<p>In numerous applications the most critical step between studying soil structure with the help of X-ray tomography and its quantitative analysis is image segmentation; the simplest type is a division of the gray-scale images into solids and pores – or binarization, is necessary to perform pore-scale simulations (Gerke et al.,2018). This can be performed by either manual or automatic methods. Current state-of-the-art methods mainly include so called local segmentation where for each two phases one needs two confidence thresholds, i.e., 100% pores and 100% solids for binarization. These thresholds are either chosen manually (Karsanina et al.,2018) or automatically, the pixels/voxels in between these thresholds are classified according to some statistical measure or by growing phases from seeds. In case of global methods there is a single threshold that divides the histogram into pores and solids explicitly. There is, however, a class of popular automatic global/local methods based on gray-scale image variance minimization – Otsu’s method and its variations (Hapca et al.,2013), numerous related techniques are available in popular image processing software – ImageJ and SoilJ (Koestel,2018). The aims of our work to test Otsu-based techniques applicability to various soils and imaging resolutions.</p><p>In our study, we compared the results of using different variations of Otsu’s method working for 2D and fully 3D images for a number of soil samples of different sizes and taken at different resolutions: 240, 100, 16, 1µm. The largest samples - monoliths with a diameter of 10 cm were taken with the coarsest resolution, mesopores were segmented in micromonoliths with a diameter of 2 cm, with the most detailed resolution the pore space of microaggregates was investigated and segmented (fraction 2-1 mm). All objects of study have individual characteristics.</p><p>According to the results of the study, it can be argued that the Otsu method (3D) with a high degree of reliability worked only for detailed images of microaggregates. Its usage for all soils is generally unacceptable, as we observed for all other samples studied here. Moreover, automatic Otsu and related methods do not perform satisfactory on images with histograms resembling highly hierarchical structures (Gerke et al.,2015), which is true for all structured soils (Karsanina et al.,2018).</p><p>This research was supported by the RSF grant 19-74-10070.</p><p>References:</p><p>Karsanina, M.V., Gerke, K.M., Skvortsova, E.B., Ivanov, A.L., & Mallants,D.(2018). Enhancing image resolution of soils by stochastic multiscale image fusion. Geoderma,314, 138-145.</p><p>Gerke, K.M., Karsanina, M.V., & Mallants, D. (2015). Universal stochastic multiscale image fusion: an example application for shale rock. Scientific reports,5, 15880.</p><p>Hapca, S.M., Houston, A.N., Otten, W., & Baveye, P.C. (2013). New local thresholding method for soil images by minimizing grayscale intra-class variance. Vadose Zone Journal,12(3).</p><p>Gerke, K.M., Vasilyev, R.V., Khirevich, S., Collins, D., Karsanina, M.V., Sizonenko, T.O., Korost D.V., Lamontagne S., & Mallants, D.(2018). Finite-difference method Stokes solver (FDMSS) for 3D pore geometries: Software development, validation and case studies. Computers & Geosciences, 114, 41-58</p><p>Koestel, J.(2018). SoilJ: an ImageJ plugin for the semiautomatic processing of three-dimensional X-ray images of soils. Vadose Zone Journal,17(1).</p>

Correlations of magnetic pore fabrics with pore fabrics derived from high-resolution X-ray computed tomography and with permeability anisotropy in sedimentary rocks and synthetic samples

2021 ◽  
Author(s):  
Yi Zhou ◽  
Michele Pugnetti ◽  
Anneleen Foubert ◽  
Pierre Lanari ◽  
Christoph Neururer ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Pore Structure ◽  
Pore Space ◽  
Sedimentary Rocks ◽  
Second Order ◽  
Indirect Measure ◽  
X Ray ◽  
Digital Rock ◽  
X Ray Computed ◽  
Permeability Anisotropy

<p>Magnetic pore fabrics (MPF) are an indirect measure of the 3D pore structure. They are defined by measuring anisotropy of magnetic susceptibility after samples have been impregnated with ferrofluid. Previous studies proposed that MPFs target pores down to 10 nm. Therefore, the method complements X-ray computed tomography (XRCT) datasets, with resolution on the order of 1-10 µm. Empirical relationships exist between MPF and pore fabric, and between MPF and permeability anisotropy. This study investigates quantitative correlations between these three properties, and between measured quantities and digital-rock-model-simulations of permeability anisotropy and MPF. Samples used for this study include natural sedimentary rocks and synthetic samples. Sediments are Plio-Pleistocene calcarenite (Apulia, Italy) with ~50% porosity and complex pore structure, and Upper Marine Molasse sandstone (Belpberg, Switzerland) with 10-20% porosity and relatively homogeneous pore space properties. Synthetic samples were made from quartz sand and calcite powder in different proportions, to simulate sandstone and carbonate rocks. Samples were characterized by pycnometry, XRCT scans, MPF determination and directional permeability measurements to obtain porosity, digital rock models, MPFs and permeability anisotropy. Porosity, permeability anisotropy, and MPFs were also computed based on digital rock models derived from XRCT data, and compared to direct measurements. Permeability anisotropy and MPF are both second-order tensors, representing the average property of the entire sample. To directly relate the XRCT-derived individual pore properties to these second-order tensor quantities, a total shape ellipsoid was computed by adding the second-order tensors reflecting the best-fit ellipsoids of single pores. Once all properties were described by second-order tensors, they were correlated in terms of fabric orientation, degree and shape of anisotropy. The MPF and total shape ellipsoids are coaxial when the samples have sufficiently large pores to be resolved, and good impregnation efficiency, and as expected, total shape ellipsoids have larger anisotropy degree. Preliminary results further indicate that the permeability anisotropy is partly consistent with total shape ellipsoids and MPFs. The defined quantitative relationships facilitate the interpretation of MPF data, thus making the method more applicable to geological and fluid migration studies.</p>

Direct visualization of phase-separated domains in lipid membranes

1978 ◽  
Vol 36 (2) ◽  
pp. 290-291
Author(s):  
S. W. Hui ◽  
T. P. Stewart
Keyword(s):  
Lipid Membranes ◽  
Structural Information ◽  
Freeze Fracture ◽  
Biological Molecules ◽  
Vacuum Drying ◽  
Direct Visualization ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
X Ray ◽  
Hydrocarbon Chains

Direct electron microscopic study of biological molecules has been hampered by such factors as radiation damage, lack of contrast and vacuum drying. In certain cases, however, the difficulties may be overcome by using redundent structural information from repeating units and by various specimen preservation methods. With bilayers of phospholipids in which both the solid and fluid phases co-exist, the ordering of the hydrocarbon chains may be utilized to form diffraction contrast images. Domains of different molecular packings may be recgnizable by placing properly chosen filters in the diffraction plane. These domains would correspond to those observed by freeze fracture, if certain distinctive undulating patterns are associated with certain molecular packing, as suggested by X-ray diffraction studies. By using an environmental stage, we were able to directly observe these domains in bilayers of mixed phospholipids at various temperatures at which their phases change from misible to inmissible states.

Correlation of Pore Structure and Permeability by SEM-Image Analysis

1990 ◽  
Vol 48 (1) ◽  
pp. 428-429
Author(s):  
C. A. Callender ◽  
Wm. C. Dawson ◽  
J. J. Funk
Keyword(s):  
Image Analysis ◽  
Pore Structure ◽  
Imaging System ◽  
Pore Space ◽  
Simulation Models ◽  
Image Analyzer ◽  
Imaging Data ◽  
Sem Images ◽  
Thin Sections ◽  
Rock Types

The geometric structure of pore space in some carbonate rocks can be correlated with petrophysical measurements by quantitatively analyzing binaries generated from SEM images. Reservoirs with similar porosities can have markedly different permeabilities. Image analysis identifies which characteristics of a rock are responsible for the permeability differences. Imaging data can explain unusual fluid flow patterns which, in turn, can improve production simulation models.Analytical SchemeOur sample suite consists of 30 Middle East carbonates having porosities ranging from 21 to 28% and permeabilities from 92 to 2153 md. Engineering tests reveal the lack of a consistent (predictable) relationship between porosity and permeability (Fig. 1). Finely polished thin sections were studied petrographically to determine rock texture. The studied thin sections represent four petrographically distinct carbonate rock types ranging from compacted, poorly-sorted, dolomitized, intraclastic grainstones to well-sorted, foraminiferal,ooid, peloidal grainstones. The samples were analyzed for pore structure by a Tracor Northern 5500 IPP 5B/80 image analyzer and a 80386 microprocessor-based imaging system. Between 30 and 50 SEM-generated backscattered electron images (frames) were collected per thin section. Binaries were created from the gray level that represents the pore space. Calculated values were averaged and the data analyzed to determine which geological pore structure characteristics actually affect permeability.

Characterizations of Synthetic 8mol% YSZ with Comparison to 3mol %YSZ for HT-SOFC

2020 ◽  
Vol 38 (4A) ◽  
pp. 491-500
Author(s):  
Abeer F. Al-Attar ◽  
Saad B. H. Farid ◽  
Fadhil A. Hashim
Keyword(s):  
Ionic Conductivity ◽  
Electrochemical Impedance ◽  
Structural Information ◽  
Impedance Analysis ◽  
High Energy ◽  
Yttria Stabilized Zirconia ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
Powder Morphology ◽  
X Ray

In this work, Yttria (Y2O3) was successfully doped into tetragonal 3mol% yttria stabilized Zirconia (3YSZ) by high energy-mechanical milling to synthesize 8mol% yttria stabilized Zirconia (8YSZ) used as an electrolyte for high temperature solid oxide fuel cells (HT-SOFC). This work aims to evaluate the densification and ionic conductivity of the sintered electrolytes at 1650°C. The bulk density was measured according to ASTM C373-17. The powder morphology and the microstructure of the sintered electrolytes were analyzed via Field Emission Scanning Electron Microscopy (FESEM). The chemical analysis was obtained with Energy-dispersive X-ray spectroscopy (EDS). Also, X-ray diffraction (XRD) was used to obtain structural information of the starting materials and the sintered electrolytes. The ionic conductivity was obtained through electrochemical impedance spectroscopy (EIS) in the air as a function of temperatures at a frequency range of 100(mHz)-100(kHz). It is found that the 3YSZ has a higher density than the 8YSZ. The impedance analysis showed that the ionic conductivity of the prepared 8YSZ at 800°C is0.906 (S.cm) and it was 0.214(S.cm) of the 3YSZ. Besides, 8YSZ has a lower activation energy 0.774(eV) than that of the 3YSZ 0.901(eV). Thus, the prepared 8YSZ can be nominated as an electrolyte for the HT-SOFC.

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