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  • 1
    Language: English
    In: Computational Geosciences, 2010, Vol.14(1), pp.15-30
    Description: Image analysis of three-dimensional microtomographic image data has become an integral component of pore scale investigations of multiphase flow through porous media. This study focuses on the validation of image analysis algorithms for identifying phases and estimating porosity, saturation, solid surface area, and interfacial area between fluid phases from gray-scale X-ray microtomographic image data. The data used in this study consisted of (1) a two-phase high precision bead pack from which porosity and solid surface area estimates were obtained and (2) three-phase cylindrical capillary tubes of three different radii, each containing an air–water interface, from which interfacial area was estimated. The image analysis algorithm employed here combines an anisotropic diffusion filter to remove noise from the original gray-scale image data, a k-means cluster analysis to obtain segmented data, and the construction of isosurfaces to estimate solid surface area and interfacial area. Our method was compared with laboratory measurements, as well as estimates obtained from a number of other image analysis algorithms presented in the literature. Porosity estimates for the two-phase bead pack were within 1.5% error of laboratory measurements and agreed well with estimates obtained using an indicator kriging segmentation algorithm. Additionally, our method estimated the solid surface area of the high precision beads within 10% of the laboratory measurements, whereas solid surface area estimates obtained from voxel counting and two-point correlation functions overestimated the surface area by 20–40%. Interfacial area estimates for the air–water menisci contained within the capillary tubes were obtained using our image analysis algorithm, and using other image analysis algorithms, including voxel counting, two-point correlation functions, and the porous media marching cubes. Our image analysis algorithm, and other algorithms based on marching cubes, resulted in errors ranging from 1% to 20% of the analytical interfacial area estimates, whereas voxel counting and two-point correlation functions overestimated the analytical interfacial area by 20–40%. In addition, the sensitivity of the image analysis algorithms on the resolution of the microtomographic image data was investigated, and the results indicated that there was little or no improvement in the comparison with laboratory estimates for the resolutions and conditions tested.
    Keywords: Multiphase flow ; Porous media ; Computed microtomography ; Image analysis ; Marching cubes
    ISSN: 1420-0597
    E-ISSN: 1573-1499
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  • 2
    Language: English
    In: Advances in Water Resources, September 2012, Vol.46, pp.55-62
    Description: ► Computed tomography datasets were analyzed for interfacial curvature. ► Curvature and transducer-based measurements compare well. ► Disconnected and connected phase interfaces have significantly different curvatures. ► Connected phase interfacial curvature relaxes as the system equilibrates. Synchrotron-based tomographic datasets of oil–water drainage and imbibition cycles have been analyzed to quantify phase saturations and interfacial curvature as well as connected and disconnected fluid configurations. This allows for close observation of the drainage and imbibition processes, assessment of equilibrium states, and studying the effects of fluid phase disconnection and reconnection on the resulting capillary pressures and interfacial curvatures. Based on this analysis estimates of capillary pressure calculated from interfacial curvature can be compared to capillary pressure measured externally with a transducer. Results show good agreement between curvature-based and transducer-based measurements when connected phase interfaces are considered. Curvature measurements show a strong dependence on whether an interface is formed by connected or disconnected fluid and the time allowed for equilibration. The favorable agreement between curvature-based and transducer-based capillary pressure measurements shows promise for the use of image-based estimates of capillary pressure for interfaces that cannot be probed with external transducers as well as opportunities for a detailed assessment of interfacial curvature during drainage and imbibition.
    Keywords: Capillary Pressure ; Interfacial Curvature ; Young–Laplace ; Drainage ; Imbibition ; Computed Microtomography ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 3
    Language: English
    In: Advances in Water Resources, April 2018, Vol.114, pp.249-260
    Description: We present an improved method for estimating interfacial curvatures from x-ray computed microtomography (CMT) data that significantly advances the potential for this tool to unravel the mechanisms and phenomena associated with multi-phase fluid motion in porous media. CMT data, used to analyze the spatial distribution and capillary pressure–saturation ( – ) relationships of liquid phases, requires accurate estimates of interfacial curvature. Our improved method for curvature estimation combines selective interface modification and distance weighting approaches. It was verified against synthetic (analytical computer-generated) and real image data sets, demonstrating a vast improvement over previous methods. Using this new tool on a previously published data set (multiphase flow) yielded important new insights regarding the pressure state of the disconnected nonwetting phase during drainage and imbibition. The trapped and disconnected non-wetting phase delimits its own hysteretic – curve that inhabits the space within the main hysteretic – loop of the connected wetting phase. Data suggests that the pressure of the disconnected, non-wetting phase is strongly modified by the pore geometry rather than solely by the bulk liquid phase that surrounds it.
    Keywords: Multiphase Flow ; Porous Media ; Computed Microtomography ; Curvature ; Capillary Pressure Measurement ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 4
    Language: English
    In: 2012
    Description: Acknowledgment is made to the Donors of the American ChemicalSociety Petroleum Research Fund for support (or partial support)of this research (grant number 48505-AC9) and by US NSF(EAR 337711 and EAR 0610108). Microtomography was performedat GeoSoilEnviroCARS (Sector 13), Advanced Photon Source (APS),Argonne National Laboratory. GeoSoilEnviroCARS is supported by the National Science Foundation-Earth Sciences (EAR-0217473),Dept. of Energy-Geosciences (DE-FG01-94ER14466) and the Stateof Illinois. Additionally, we would like to acknowledge the followingpeople for their help with either collecting the data: Mark Rivers(GSECARS APS/University of Chicago), or with interpreting theresults: James McClure (University of North Carolina), Casey Miller(University of North Carolina), William Gray (University of NorthCarolina), and Adrian Sheppard (Australian National University).
    Description: Synchrotron-based tomographic datasets of oil–water drainage and imbibition cycles have been analyzed to quantify phase saturations and interfacial curvature as well as connected and disconnected fluid configurations. This allows for close observation of the drainage and imbibition processes, assessment of equilibrium states, and studying the effects of fluid phase disconnection and reconnection on the resulting capillary pressures and interfacial curvatures. Based on this analysis estimates of capillary pressure calculated from interfacial curvature can be compared to capillary pressure measured externally with a transducer. Results show good agreement between curvature-based and transducer-based measurements when connected phase interfaces are considered. Curvature measurements show a strong dependence on whether an interface is formed by connected or disconnected fluid and the time allowed for equilibration. The favorable agreement between curvature-based and transducer-based capillary pressure measurements shows promise for the use of image-based estimates of capillary pressure for interfaces that cannot be probed with external transducers as well as opportunities for a detailed assessment of interfacial curvature during drainage and imbibition.
    Description: This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/advances-in-water-resources/. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. ; 10.1016/j.advwatres.2012.05.009
    Keywords: Drainage ; Computed Microtomography ; Capillary Pressure ; Young–Laplace ; Interfacial Curvature ; Imbibition
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 5
    Language: English
    In: Advances in Water Resources, 2009, Vol.32(11), pp.1632-1640
    Description: Hysteresis in the relationship between capillary pressure , wetting phase saturation and nonwetting–wetting interfacial area per volume is investigated using multiphase lattice-Boltzmann simulations of drainage and imbibition in a glass bead porous system. In order to validate the simulations, the and main hysteresis loops were compared to experimental data reported by Culligan et al. [Culligan KA, Wildenschild D, Christensen BS, Gray WG, Rivers ML, Tompson AB. Interfacial area measurements for unsaturated flow through porous media. Water Resour Res 2004;40:W12413]. In general, the comparison shows that the simulations are reliable and capture the important physical processes in the experimental system. curves, curves and phase distributions (within the pores) show good agreement during drainage, but less satisfactory agreement during imbibition. Drainage and imbibition scanning curves were simulated in order to construct surfaces. The root mean squared error (RMSE) and mean absolute error (MAE) between drainage and imbibition surfaces was 0.10 mm and 0.03 mm , respectively. This small difference indicates that hysteresis is virtually nonexistent in the relationship for the multiphase system studied here. Additionally, a surface was fit to the main loop (excluding scanning curves) of the drainage and imbibition data and compared to the surface fit to all of the data. The differences between these two surfaces were small (RMSE = 0.05 mm and MAE = 0.01 mm ) indicating that the surface is adequately represented without the need for the scanning curve data, which greatly reduces the amount of data required to construct the non-hysteretic surface for this data.
    Keywords: Multiphase Flow ; Lattice-Boltzmann ; Interfacial Area ; Capillary Pressure ; Porous Media ; Computed Microtomography ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 6
    Language: English
    In: Advances in water resources, 2009, Vol.32, pp.1632-1640
    Description: Includes references ; p. 1632-1640.
    Keywords: Hysteresis ; Computed Tomography ; Porous Media ; Drainage ; Water Flow ; Mathematical Models ; Unsaturated Conditions ; Simulation Models ; Unsaturated Flow ; Lattice-Boltzmann Simulation ; Capillary Pressure ; Capillary Pressure-Saturation-Interfacial Relationship ; Computed Microtomography
    ISSN: 0309-1708
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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