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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
    In: Geophysical Research Letters, 16 January 2016, Vol.43(1), pp.196-205
    Description: We recreate three‐phase reservoir conditions (high‐pressure/temperature) using a microfluidics system and show that the use of scCO for restimulation operations, such as hydraulic fracturing, can enhance mixing and production. The results inform hydrocarbon extraction from deep shale formations, which has recently generated an energy boom that has lowered hydrocarbon costs. However, production decreases rapidly and methods to increase efficiency or allow restimulation of wells are needed. In our experiments, the presence of residual brine from initial production creates spatiotemporal variability in the system that causes the injected scCO to more effectively interact‐mix with trapped hydrocarbon, thereby increasing recovery. We apply volume‐averaging techniques to upscale brine saturation, which allows us to analyze the complex three‐phase system in the framework of well characterized two‐phase systems. The upscaled three‐phase system behaves like a two‐phase system: greater mixing with larger non‐wetting content and higher heterogeneity. The results are contrary to previous observations in water‐wet systems. Mixing in three‐phase systems Residual brine enhances mixing between scCO2 and hydrocarbons in oil‐wet rocks Restimulation operations in hydraulic fracturing: Alternatives to water
    Keywords: Porous Media ; Multiphase ; Mixing ; Fossil Fuels ; Restimulation
    ISSN: 0094-8276
    E-ISSN: 1944-8007
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  • 3
    Language: English
    In: Physical review. E, Statistical, nonlinear, and soft matter physics, September 2012, Vol.86(3 Pt 2), pp.036701
    Description: This work focuses on an improved multicomponent interparticle-potential lattice Boltzmann model. The model results in viscosity-independent equilibrium densities and is capable of simulating kinematic viscosity ratios greater than 1000. External forces are incorporated into the discrete Boltzmann equation, rather than through an equilibrium velocity shift as in the original Shan and Chen (hereafter, SC) model. The model also requires the derivation of a momentum conserving effective velocity, which is substituted into the equilibrium distribution function and applies to both the single- and multiple-relaxation-time formulations. Additionally, higher-order isotropy is used in the calculation of the fluid-fluid interaction forces to reduce the magnitude of spurious currents (i.e., numerical errors) in the vicinity of interfaces. First, we compare the model to the SC model for static bubble simulations. We demonstrate that the model results in viscosity-independent equilibrium bubble densities for a wide range of kinematic viscosities, which is not the case for the SC model. Furthermore, we show that the model is capable of simulating stable bubbles for kinematic viscosity ratios greater than 1000 (when higher-order isotropy is used), whereas the SC model is known to be limited to kinematic viscosity ratios on the order of 10. Next we verify the model for surface tension via Laplace's law and show that the model results in the same surface tension values for a range of kinematic viscosities and kinematic viscosity ratios of 10, 100, and 1000. The model is also verified for layered cocurrent flow though parallel plates. We show that the simulated velocity profiles preserve continuity at the interface for kinematic viscosity ratios ranging from 0.001 to 1000 and that the model accurately predicts nonwetting and wetting phase relative permeability for kinematic viscosity ratios of 0.01 to 100.
    Keywords: Algorithms ; Models, Chemical ; Viscosity ; Rheology -- Methods ; Solutions -- Chemistry
    ISSN: 24700045
    E-ISSN: 1550-2376
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  • 4
    Language: English
    In: Advances in Water Resources, Sept, 2012, Vol.46, p.55(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.advwatres.2012.05.009 Byline: Ryan T. Armstrong (a), Mark L. Porter (b), Dorthe Wildenschild (a) Keywords: Capillary pressure; Interfacial curvature; Young-Laplace; Drainage; Imbibition; Computed microtomography Abstract: a* Computed tomography datasets were analyzed for interfacial curvature. a* Curvature and transducer-based measurements compare well. a* Disconnected and connected phase interfaces have significantly different curvatures. a* Connected phase interfacial curvature relaxes as the system equilibrates. Author Affiliation: (a) School of Chemical, Biological, and Environmental Engineering, Oregon State University, 103 Gleeson Hall Corvallis, OR 97331-2702, United States (b) Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM 87545, United States Article History: Received 12 December 2011; Revised 18 May 2012; Accepted 18 May 2012
    ISSN: 0309-1708
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Computational Geosciences, 2014, Vol.18(1), pp.17-27
    Description: The lattice Boltzmann method is a popular tool for pore-scale simulation of flow. This is likely due to the ease of including complex geometries such as porous media and representing multiphase and multifluid flows. Many advancements, including multiple relaxation times, increased isotropy, and others have improved the accuracy and physical fidelity of the method. Additionally, the lattice Bolzmann method is computationally very efficient, thanks to the explicit nature of the algorithm and relatively large amount of local work. The combination of many algorithmic options and efficiency means that a software framework enabling the usage and comparison of these advancements on computers from laptops to large clusters has much to offer. In this paper, we introduce Taxila LBM , an open-source software framework for lattice Boltzmann simulations. We discuss the design of the framework and lay out the features available, including both methods in the literature and a few new enhancements which generalize methods to complex geometries. We discuss the trade-off of accuracy and performance in various methods, noting how the Taxila LBM makes it easy to perform these comparisons for real problems. And finally, we demonstrate a few common applications in pore-scale simulation, including the characterization of permeability of a Berea sandstone and analysis of multifluid flow in heterogenous micromodels.
    Keywords: Pore-scale simulation ; Lattice Boltzmann method ; Software framework
    ISSN: 1420-0597
    E-ISSN: 1573-1499
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  • 6
    Language: English
    In: Transport in Porous Media, 2011, Vol.88(1), pp.1-30
    Description: The concept of tortuosity is an integral part of models that describe transport in multiscale systems. Traditionally, tortuosity is defined as the ratio of an effective path length to the shortest path length in the microstructure. While the shortest path length can be unambiguously specified, the same is not true for the effective path length, since it changes from one type of transport to another. Consequently, it is possible to have different values of tortuosity for different transport processes taking place in the same system. This is convenient since, under this approach, different transport processes can involve the same type of filters of the microscale information, but the nature of such information is what characterizes each type of transport process. In order to avoid running into unclear interpretations, a set of tortuosity rules are proposed, which relate this concept only to the microscale geometry. On the basis of these rules, we examine the pertinence of introducing the tortuosity concept in mass transport. In particular, we study mass diffusion with and without chemical reaction and convection in porous media. Of all these cases, our analysis indicates that the concept of tortuosity is only adequate for passive diffusion, since in the other cases there is an unavoidable coupling of the transport phenomena that determine the effective path of the solute.
    Keywords: Tortuosity ; Volume averaging ; Dispersion ; Diffusion ; Reaction
    ISSN: 0169-3913
    E-ISSN: 1573-1634
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  • 7
    Language: English
    In: Transport in Porous Media, 2011, Vol.89(1), pp.135-137
    Description: Byline: Francisco J. Valdes-Parada (1), Mark L. Porter (2), Brian D. Wood (3) Author Affiliation: (1) Area de Ingenieria en Recursos Energeticos, Universidad Autonoma Metropolitana-Iztapalapa, Mexico, D.F., 09340, Mexico (2) EES-14, MS D462, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA (3) School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR, 97331, USA Article History: Registration Date: 17/05/2011 Online Date: 08/06/2011 Article note: The online version of the original article can be found under doi: 10.1007/s11242-010-9613-9.
    Keywords: Earth Sciences ; Hydrogeology ; Classical Continuum Physics ; Industrial Chemistry/Chemical Engineering ; Geotechnical Engineering ; Civil Engineering ; Chemistry ; Physics;
    ISSN: 0169-3913
    E-ISSN: 1573-1634
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  • 8
    Language: English
    In: International Journal of Greenhouse Gas Control, August 2015, Vol.39, pp.51-61
    Description: The physicochemical processes associated with CO leakage into shallow aquifer systems are complex and span multiple spatial and time scales. Continuum-scale numerical models that faithfully represent the underlying pore-scale physics are required to predict the long-term behavior and aid in risk analysis regarding regulatory and management decisions. This study focuses on benchmarking the numerical simulator, FEHM, with intermediate-scale column experiments of CO gas evolution in homogeneous and heterogeneous sand configurations. Inverse modeling was conducted to calibrate model parameters and determine model sensitivity to the observed steady-state saturation profiles. It is shown that FEHM is a powerful tool that is capable of capturing the experimentally observed outflow rates and saturation profiles. Moreover, FEHM captures the transition from single- to multi-phase flow and CO gas accumulation at interfaces separating sands. We also derive a simple expression, based on Darcy's law, for the pressure at which CO free phase gas is observed and show that it reliably predicts the location at which single-phase flow transitions to multi-phase flow.
    Keywords: Carbon Sequestration ; Co2 Leakage ; Exsolution ; Multiphase Flow ; Fehm ; Engineering
    ISSN: 1750-5836
    E-ISSN: 1878-0148
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  • 9
    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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  • 10
    In: Journal of Fluid Mechanics, 2016, Vol.805, pp.118-146
    Description: We report on a refined macroscopic model for slightly compressible gas slip flow in porous media developed by upscaling the pore-scale boundary value problem. The macroscopic model is validated by comparisons with an analytic solution on a two-dimensional (2-D) ordered model structure and with direct numerical simulations on random microscale structures. The symmetry properties of the apparent slip-corrected permeability tensor in the macroscale momentum equation are analysed. Slip correction at the macroscopic scale is more accurately described if an expansion in the Knudsen number, beyond the first order considered so far, is employed at the closure level. Corrective terms beyond the first order are a signature of the curvature of solid–fluid interfaces at the pore scale that is incompletely captured by the classical first-order correction at the macroscale. With this expansion, the apparent slip-corrected permeability is shown to be the sum of the classical intrinsic permeability tensor and tensorial slip corrections at the successive orders of the Knudsen number. All the tensorial effective coefficients can be determined from intrinsic and coupled but easy-to-solve closure problems. It is further shown that the complete form of the slip boundary condition at the microscale must be considered and an important general feature of this slip condition at the different orders in the Knudsen number is highlighted. It justifies the importance of slip-flow correction terms beyond the first order in the Knudsen number in the macroscopic model and sheds more light on the physics of slip flow in the general case, especially for large porosity values. Nevertheless, this new nonlinear dependence of the apparent permeability with the Knudsen number should be further verified experimentally.
    Keywords: Papers; Low-Reynolds-Number Flows; Porous Media; Rarefied Gas Flow
    ISSN: 0022-1120
    E-ISSN: 1469-7645
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