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  • 1
    Electronic Resource
    Electronic Resource
    A Simple Model for the Variation of Permeability due to Partial Saturation in Dual Scale Porous Media (1997)
    Springer
    Transport in porous media 27 (1997), S. 243-264 
    Details
    ISSN: 1573-1634
    Keywords: permeability ; Darcy's law ; unsaturated flow ; dual scale ; resin transfer molding ; liquid injection molding.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The main focus of this work is to model macroscopically the effects of partial saturation upon the permeability of dual scale fibrous media made of fiber bundles when a Newtonian viscous fluid impregnates it. A new phenomenological model is proposed to explain the discrepancies between experimental pressure results and analytical predictions based on Darcy's law. This model incorporates the essential features of relative permeability but without the necessity of measuring saturation of the liquid for its prediction. The model is very relevant for the small scale industrial systems where a liquid is forced to flow through a fibrous porous medium. It requires four parameters. Two of them are the two permeability values based on the two length scales. One length scale is of the order of magnitude of the individual fiber radius and corresponds to the permeability of the completely staurated medium, the other is of the order of magnitude of the distance between the fiber bundles and corresponds to the permeability of the partially saturated medium. The other two parameters are the lengths of the two partially saturated regions of the flow domain. The two lengths of the partially saturated region and the permeability of the fully saturated flow domain can be directly measured from the experiments. The excellent agreement between the model and the experimental results of inlet pressure profile with respect to time suggests that this model may be used to describe the variation of the permeability behind a moving front in such porous media for correct pressure prediction. It may also be used to characterize the fibrous medium by determining the two different permeabilities and the relative importance of the unsaturated portion of the flow domain for a given architecture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006544107324
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  • 2
    Electronic Resource
    Electronic Resource
    The thermogravitational effect in porous media: A modelling approach (1992)
    Springer
    Transport in porous media 9 (1992), S. 223-240 
    Details
    ISSN: 1573-1634
    Keywords: Thermodiffusion ; Soret effect ; thermogravitational effect ; irreversible thermodynamics ; porous medium ; permeability ; transport model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The thermogravitational effect may induce large concentration contrasts, particularly in porous media. This phenomenon arises from a coupling of the Soret effect and convection currents in a temperature field. The present study of this phenomenon is motivated by the safety assessment of nuclear waste repositories, which are sources of thermal energy. Here, we present a modelling approach of laboratory experiments carried out at the University of Toulouse. The results of this model, though more adequate than the analytical solution to account for the influence of permeability, remain far from the experimental ones. In conclusion, it appears that the research must now focus on both a comprehensive phenomenology of the transport processes and experiments with new dimensional constraints.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611968
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  • 3
    Electronic Resource
    Electronic Resource
    Mean field calculation of effective permeability based on fractal pore space (1992)
    Springer
    Transport in porous media 8 (1992), S. 93-97 
    Details
    ISSN: 1573-1634
    Keywords: Porous rock ; permeability ; porosity ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Effective permeability for porous rocks is calculated using mean field theory. We make two simplifying assumptions about the internal conductances in a network representation of the porous rock: (i) Pore space is characterized by a uniform fractal scaling; (ii) the internal conductances depend only on the characteristic pore sizes. Within these approximations, it is possible to derive a simple probability density for the internal conductances which is used for calculating effective permeability. Good agreement between calculations and experimental data of permeability vs. porosity is achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616894
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  • 4
    Electronic Resource
    Electronic Resource
    Implication of fractal geometry for fluid flow properties of sedimentary rocks (1992)
    Springer
    Transport in porous media 8 (1992), S. 133-147 
    Details
    ISSN: 1573-1634
    Keywords: Fractal ; multifractal ; sedimentary rocks ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract It is demonstrated that a certain amount of order can be extracted from an apparently random distribution of pores in sedimentary rocks by exploiting the scaling characteristics of the geometry of the porespace with the help of fractal statistics. A simple fractal model of a sedimentary rock is built, and is tested against both the Archie law for conductivity and the Carman-Kozeny equation for permeability. We demonstrate how multifractal scaling of pore-volume can be used as a tool for rock characterization by computing its experimentalf(α) spectrum, which can be modelled by a simple two-scale Cantor set.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617114
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  • 5
    Electronic Resource
    Electronic Resource
    Effective-medium treatment of flow through anisotropic fracture system — Improved permeability estimates using a new lattice mapping (1992)
    Springer
    Transport in porous media 9 (1992), S. 287-295 
    Details
    ISSN: 1573-1634
    Keywords: Anisotropic fracture system ; effective medium theory ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The permeability tensor of a fractured reservoir, which will typically be anisotropic because of the presence of stress, is an important parameter to be taken into account when formulating a production strategy for the reservoir. Extensive computational effort is involved in calculating the permeabilities of model fracture systems by solving the fluid flow equations through finite realisations of the systems, and this renders a search for alternative techniques worthwhile. An attractive approach is to perform a rough mapping of the fracture system onto a lattice so that effective medium theory can be applied. For isotropic systems that are well-connected, this technique works well, but it gives increasingly poor results as the degree of anisotropy increases. In this contribution, a refinement of the lattice mapping is presented that incorporates an important aspect of the randomness present in the original system. This greatly increases the applicability of the technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611972
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  • 6
    Electronic Resource
    Electronic Resource
    Wavelet upscaling based on piecewise bilinear approximation of the permeability field (1996)
    Springer
    Transport in porous media 23 (1996), S. 125-134 
    Details
    ISSN: 1573-1634
    Keywords: permeability ; upscaling ; flow prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A method for upscaling of permeability in heterogeneous porous media is presented. The upscaled field takes the form K = e Y , where Y, in two dimensions, is a piecewise bilinear function. The method is tested on a number of random permeability fields, with different integral scale/correlation length and variance. The numerical results show that this method conserves much more of the heterogeneous fingering than classical block-based upscaling methods, e.g., geometric mean.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178122
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  • 7
    Electronic Resource
    Electronic Resource
    Permeability evolution induced by the precipitation of an advected solute: Effect of the microscopic and the macroscopic scales competition on the clogging mechanism (1996)
    Springer
    Transport in porous media 24 (1996), S. 341-375 
    Details
    ISSN: 1573-1634
    Keywords: precipitation ; porous medium ; clogging ; feedback mechanism ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A model is proposed for coupling the one-dimensional transport of solute with surface precipitation kinetics which induces the clogging of an initially homogeneous porous medium. The aim is to focus the non-linear feedback effect between the transport and the chemical reaction through the permeability of the medium. A Lagrangian formulation, used to solve the coupled differential equations, gives semi-analytical expressions of the hydrodynamic quantities. A detailed analysis reveals that the competition between the microscopic and macroscopic scales controls the clogging mechanism, which differs depends on whether short or long times are considered. In order to illustrate this analysis, more quantitative results were obtained in the case of a second and zeroth order kinetic. It was necessary to circumvent the semi-analytic character of the solutions problem by successive approximation. A comparison with results obtained by simulations displays a good agreement during the most part of the clogging time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154097
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  • 8
    Electronic Resource
    Electronic Resource
    Two-phase flow in heterogeneous porous media: The method of large-scale averaging (1988)
    Springer
    Transport in porous media 3 (1988), S. 357-413 
    Details
    ISSN: 1573-1634
    Keywords: Two-phase flow ; heterogeneous porous media ; large-scale averaging ; permeability ; capillary pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The analysis of two-phase flow in porous media begins with the Stokes equations and an appropriate set of boundary conditions. Local volume averaging can then be used to produce the well known extension of Darcy's law for two-phase flow. In addition, a method of closure exists that can be used to predict the individual permeability tensors for each phase. For a heterogeneous porous medium, the local volume average closure problem becomes exceedingly complex and an alternate theoretical resolution of the problem is necessary. This is provided by the method of large-scale averaging which is used to average the Darcy-scale equations over a region that is large compared to the length scale of the heterogeneities. In this paper we present the derivation of the large-scale averaged continuity and momentum equations, and we develop a method of closure that can be used to predict the large-scale permeability tensors and the large-scale capillary pressure. The closure problem is limited by the principle of local mechanical equilibrium. This means that the local fluid distribution is determined by capillary pressure-saturation relations and is not constrained by the solution of an evolutionary transport equation. Special attention is given to the fact that both fluids can be trapped in regions where the saturation is equal to the irreducible saturation, in addition to being trapped in regions where the saturation is greater than the irreducible saturation. Theoretical results are given for stratified porous media and a two-dimensional model for a heterogeneous porous medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233177
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of NAPL Contaminants on the Permeability of a Soil‐Bentonite Slurry Wall Material (2000)
    Springer
    Transport in porous media 38 (2000), S. 43-56 
    Details
    ISSN: 1573-1634
    Keywords: NAPL ; hydraulic conductivity ; permeability ; slurry walls ; soil ; bentonite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Soil‐bentonite slurry walls are designed to inhibit the subsurface movement of contaminants from hazardous waste sites. Although it is generally accepted that high concentrations of organic compounds will adversely affect soil‐bentonite slurry walls and clay liners, previous research investigating the effects of NAPLs on the conductivity of clay wall materials has been inconclusive. In this study the effects of various organics (benzene, aniline, trichloroethylene, ethylene dichloride, methylene chloride) on the effective conductivity of a typical soil‐bentonite slurry wall material were studied under two effective stress conditions, 200 and 52 kPa. The hydraulic conductivity for the soil‐bentonite material permeated with water averaged 1.52×10-8 cm s-1. Compared to water, there was little change in conductivity when the sample was permeated with a solution containing a NAPL compound at its solubility limit, except for aniline. However, there was a one to two order of magnitude decrease in conductivity when the sample was permeated with a pure NAPL for all NAPLs tested. When the soil‐bentonite material was permeated with a water/NAPL/water/NAPL sequence, the conductivity decreased one to two orders of magnitude when a NAPL was introduced following water; however, when water was reintroduced after the NAPL, the conductivity increased to the initial hydraulic conductivity. The conductivity again decreased one to two orders of magnitude when the NAPL was reintroduced. This trend occurred for all NAPLs tested, and the fluid properties of the NAPL compounds alone did not account for the decrease in conductivity compared to water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006655015509
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  • 10
    Electronic Resource
    Electronic Resource
    Data interpretation problems to be expected in the study of coupled fluid flow in porous media (1989)
    Springer
    Transport in porous media 4 (1989), S. 185-198 
    Details
    ISSN: 1573-1634
    Keywords: Transport coefficients ; coupling ; fluid flow ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract On the basis of recent work, it would appear that the transport coefficients descriptive of certain idealized cases of coupled flow of immiscible fluids in porous media, can be determined in principle by calculations employing well-defined experimental data. Other considerations show, however, that even small errors inherent in laboratory observations sometimes will have an enormously large effect on the accuracy of the calculated values. On the other hand, it often will be the case that values for the transport coefficients are not needed individually, as long as those particular functions which appear lumped together in the equations of motion, can be calculated from the same data but with less error. In any case, it will be clear that error problems will be, to some extent, mitigated when very accurate instrumentation is available to control and measure the fluxes and driving forces that give rise to the transport processes under study. Thus, the aim of this paper is to present an error analysis that will facilitate laboratory design in preparation for experimental work, and will also facilitate the interpretation of the data that eventually are to be obtained. Another aim is to underscore the risks taken by those who fail to take coupling effects into account just because the potential importance of them is not appreciated or not clearly revealed by existing data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00134996
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