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  • Porter, Mark  (9)
  • 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
    In: Water Resources Research, August 2010, Vol.46(8), pp.n/a-n/a
    Description: In this work, the constitutive relationship between capillary pressure (), saturation (), and fluid‐fluid interfacial area per volume (IFA) is characterized using computed microtomography for drainage and imbibition experiments consisting of a nonaqueous phase liquid and water. The experimentally measured relationship was compared to a thermodynamic model that relates the area under the − curve to the total IFA, , and the capillary‐associated IFA, . Surfaces were fit to the experimental and modeled − − and − − data in order to characterize the relationship in three dimensions (3D). For the experimental system, it was shown that the − − relationship does not exhibit hysteresis. The model is found to provide a reasonable approximation of the magnitude of the 3D surfaces for and , with a mean absolute percent error of 26% and 15%, respectively. The relatively high mean absolute percent errors are primarily the result of discrepancies observed at the wetting‐ and nonwetting‐phase residual saturation values. Differences in the shapes of the surfaces are noted, particularly in the curvature (arising from the addition of scanning curves and presence of − hysteresis in the predicted results) and endpoints (particularly the inherent nature of thermodynamic models to predict significant associated with residual nonwetting‐phase saturation). Overall, the thermodynamic model is shown to be a practical, inexpensive tool for predicting the − − and − − surfaces from − data.
    Keywords: Multiphase Flow ; Capillary Pressure ; Saturation ; Interfacial Area ; Microtomography ; Thermodynamic
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 4
    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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  • 5
    In: Water Resources Research, December 2007, Vol.43(12), pp.n/a-n/a
    Description: A Shan‐Chen–type multiphase lattice Boltzmann (LB) model was applied to observed computed microtomography data from water‐air and water‐Soltrol displacement experiments in a glass bead porous medium. Analysis of the Bond, Reynolds, and Capillary numbers for these systems showed that capillary forces were dominant removing the need to model viscous, gravitational, and density effects. A numerical parameterization of the LB model yielded lattice surface tension and contact angle, and appropriate pressure boundary conditions. Two scaling relations provided a link between lattice pressure and physical pressure and lattice time and physical time. Results showed that there was a good match between measured and simulated pressure‐saturation data for the water‐air system, but that there were large differences between the simulations and observations for the water‐Soltrol system. The discrepancies for the water‐Soltrol system were probably due to inconsistencies between experimental conditions and simulated conditions such as nonzero contact angle in the experiments. Analysis of saturation profiles indicated increasing saturation near the wetting boundary and decreasing saturations near the nonwetting boundary. We attribute these saturation transitions to pore‐neck and percolation effects. While computationally intensive, results of this study were very encouraging for the application of LB simulations to microscale interfacial phenomena. Future studies will carry out a further validation in terms of interfacial areas, contact lines, and fluid distributions.
    Keywords: Lattice Boltzmann ; Pressure Saturation ; Comparison
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 6
    Language: English
    Description: The capillary pressure-saturation curve is widely used to characterize hydraulic properties of porous media. It is often assumed that curves measured under equilibrium or steady-state flow conditions can be applied to transient flow conditions, and vice versa. Yet, substantial experimental evidence suggests that capillary pressure-saturation curves obtained during transient conditions differ from those obtained under equilibrium or steady-state conditions. It has been shown that the capillary pressure-saturation curve shows signs of dynamic behavior depending on the inflow and outflow rate applied to the porous system. The exact cause of the observed shift is not yet fully understood. It is hypothesized that the mechanisms responsible for dynamic behavior include: (1) the geometry of the pore space, (2) interfacial phenomena at the pore scale, and (3) the interplay of inertial and viscous forces. In this investigation, air/water and oil/water imbibition and drainage experiments were conducted on a column of packed glass beads. Various inflow and outflow rates were applied to each multi-phase system, which resulted in capillary pressure-saturation curves that exhibit varying degrees of dynamic behavior. The dynamic behavior observed in preliminary oil/water experiments was less pronounced than the behavior observed in past air/water experiments. This suggests that the viscous and inertial forces may only be a major factor when the density and...
    Source: DataCite
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  • 7
    Language: English
    Description: The capillary pressure-saturation curve is widely used to characterize hydraulic properties of porous media. It is often assumed that curves measured under equilibrium or steady-state flow conditions can be applied to transient flow conditions, and vice versa. Yet, substantial experimental evidence suggests that capillary pressure-saturation curves obtained during transient conditions differ from those obtained under equilibrium or steady-state conditions. It has been shown that the capillary pressure-saturation curve shows signs of dynamic behavior depending on the inflow and outflow rate applied to the porous system. The exact cause of the observed shift is not yet fully understood. It is hypothesized that the mechanisms responsible for dynamic behavior include: (1) the geometry of the pore space, (2) interfacial phenomena at the pore scale, and (3) the interplay of inertial and viscous forces. In this investigation, air/water and oil/water imbibition and drainage experiments were conducted on a column of packed glass beads. Various inflow and outflow rates were applied to each multi-phase system, which resulted in capillary pressure-saturation curves that exhibit varying degrees of dynamic behavior. The dynamic behavior observed in preliminary oil/water experiments was less pronounced than the behavior observed in past air/water experiments. This suggests that the viscous and inertial forces may only be a major factor when the density and...
    Source: DataCite
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  • 8
    Text Resource
    Text Resource
    XVI International Conference on Computational Methods in Water Resources
    Language: English
    Description: Recent advances in observational and computational techniques have facilitated the study of fluid dynamics and interfacial geometry in porous media. Within some experimental limitations, computed tomography X-ray (CMT) and magnetic resonance imaging (MRI) are now able to accurately map the 3D structure of porous geometries. Computational advances largely concern Lattice Boltzmann (LB) method that has been shown to be useful in simulating microscale flow in porous media. With some phenomenological or thermodynamic extensions, the LB method is also able to deal with microscale interfacial phenomena in single or multiphase systems. The goal of this presentation is to provide insight into what is needed to make a link between 3D experimental observations of interfacial geometry and LB simulations. The experimental data consist of CMT observations several Sotrol-water displacements inside a glass bead system with a resolution of 17 microns. Also available are capillary pressure-saturation curves between 0 and 1kPa. The LB model is that of Shan-Chen as modified by Martys and Chen (1996). We present the most parsimonious way to calibrate the surface tension and contact angle in the model, define space, pressure and time scaling. We will also identify potential problems relating to pore-size and digitization effects that are present in the simulations, but not in the original observations. ...
    Source: DataCite
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  • 9
    Text Resource
    Text Resource
    XVI International Conference on Computational Methods in Water Resources
    Language: English
    Description: Recent advances in observational and computational techniques have facilitated the study of fluid dynamics and interfacial geometry in porous media. Within some experimental limitations, computed tomography X-ray (CMT) and magnetic resonance imaging (MRI) are now able to accurately map the 3D structure of porous geometries. Computational advances largely concern Lattice Boltzmann (LB) method that has been shown to be useful in simulating microscale flow in porous media. With some phenomenological or thermodynamic extensions, the LB method is also able to deal with microscale interfacial phenomena in single or multiphase systems. The goal of this presentation is to provide insight into what is needed to make a link between 3D experimental observations of interfacial geometry and LB simulations. The experimental data consist of CMT observations several Sotrol-water displacements inside a glass bead system with a resolution of 17 microns. Also available are capillary pressure-saturation curves between 0 and 1kPa. The LB model is that of Shan-Chen as modified by Martys and Chen (1996). We present the most parsimonious way to calibrate the surface tension and contact angle in the model, define space, pressure and time scaling. We will also identify potential problems relating to pore-size and digitization effects that are present in the simulations, but not in the original observations. ...
    Source: DataCite
    Library Location Call Number Volume/Issue/Year Availability
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