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  • Articles  (14)
  • Articles: DFG German National Licenses  (14)
  • two-phase flow  (14)
  • 2010-2014
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  • Articles  (14)
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  • Articles: DFG German National Licenses  (14)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 17 (1994), S. 133-144 
    ISSN: 1573-1634
    Keywords: Pressure-difference equation ; immiscible ; two-phase flow ; hydrodynamic forces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Because of the influence of hydrodynamic forces, the difference in macroscopic pressure which exists, at static equilibrium, between two immiscible phases located in a porous medium may be different from that which pertains during flow. In this paper, the concept of relative pressure difference, together with a new pressure-difference equation, is used to investigate the impact that the hydrodynamic forces have on the difference in macroscopic pressure which pertains when two immiscible fluids flow simultaneously through a homogeneous, water-wet porous medium. This investigation reveals that, in general, the equation defining the difference in pressure between two flowing phases must include a term which takes proper account of the hydrodynamic effects. Moreover, it is pointed out that, while neglect of the hydrodynamic effects introduces only a small amount of error when the two fluids are flowing cocurrently, such neglect is not permissible during steady-state, countercurrent flow. This is because failure to include the impact of the hydrodynamic effects in the latter case makes it impossible to explain the pressure behaviour observed in steady-state, countercurrent flow. Finally, the results of this investigation are used as a basis for arguing that, during steady-state, countercurrent flow, saturation is uniform, as is the case of steady-state, cocurrent flow.
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  • 2
    ISSN: 1573-1634
    Keywords: two-phase flow ; ganglion dynamics ; immiscible displacement ; relative permeability ; enhanced oil recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A comparative experimental study of ‘steady-state’ two-phase flow in two types of model porous media is made to determine the effects of nonplanarity on the flow mechanisms and the mesoscopic flow behavior. The two model porous media have virtually the same pore geometry, but one has a planar network skeleton, whereas the other has a nonplanar (two-layer) skeleton. The latter is a new type of model porous medium that permits detailed visual observation and quantitative measurements without sacrificing the 3D character of the pore network topology. The capillary number and the flowrate ratio are changed systematically, whereas the viscosity ratio and the wettability (contact angle) are kept constant. Conventional relative permeabilities are determined and correlated with the porescale flow phenomena. In the range of parameter values investigated, the flow mechanism observed was ganglion dynamics (intrinsically unsteady, but giving a time-averaged steady-state). The nonplanarity is shown to have small qualitative but significant quantitative effects. In the nonplanar porous medium, the ganglion size distribution is wider, the mean ganglion size larger, and the stranded ganglia are fewer than those in the planar one, under the same flow conditions.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 15 (1994), S. 71-79 
    ISSN: 1573-1634
    Keywords: Coupling ; transport coefficients ; porous media flow ; relative permeability ; two-phase flow ; Steady-state displacement ; dynamic state displacement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The interaction between immiscible flowing phases can play a significant role in flow in porous media. Traditional relative permeability theory which does not consider the coupling effect between immiscible flowing phases, is perforce blinded to any dynamics in the flows. Therefore, the determination of the transport coefficients characterizing the coupling effect becomes crucial. Useful analytical or numerical solutions without restrictions have not been possible. Mathematical descriptions that encode the coupling effect for immiscible phase flowing in porous media become complex and unwieldy. Resort must be to experiment. A new experimental method of measuring coupling coefficients of two-phase flow in porous media is developed in this work; it is simply a combination of steady and dynamic state displacement experiments.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 17 (1994), S. 105-120 
    ISSN: 1573-1634
    Keywords: Porous medium ; two-phase flow ; steam-water flow ; saturated steam flows ; air-water flow ; relative permeability ; effective permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper presents a method and describes an experimental device for determining the steam-water relative permeabilites of unconsolidated porous media. The experimental conditions are as close as possible to those of geothermal reservoirs. The relative permeabilities have been obtained at 180 and 150
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 17 (1994), S. 121-132 
    ISSN: 1573-1634
    Keywords: Capillary pressure ; relative permeability ; immiscible ; two-phase flow ; hydrodynamic forces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Because of the influence of hydrodynamic forces, the capillary pressure measured at static equilibrium may be different from that which pertains during flow. If such is the case, it may not be permissible to use steady-state relative permeabilities to predict unsteady-state flow. In this paper, the idea that the total flux of a given phase may be partitioned into several individual fluxes, together with a new pressure difference equation, is used to explore the possible impact that the hydrodynamic forces might have on capillary pressure and, as a consequence, relative permeability. This exploration reveals that, provided the pressure difference equation is implemented properly, capillarity has no impact on the relative permeability curves for the homogeneous, water-wet porous media considered. Moreover, it is demonstrated that, if the hydrodynamic effects are neglected, very little error is introduced into the analysis.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 11 (1993), S. 201-218 
    ISSN: 1573-1634
    Keywords: Porous medium model ; two-phase flow ; Darcy's law ; relative permeabilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An idealized model of a porous rock consisting of a bundle of capillary tubes whose cross-sections are regular polygons is used to assess the importance of viscous coupling or lubrication during simultaneous oil-water flow. Fluids are nonuniformly distributed over tubes of different characteristic dimension because of the requirements of capillary equilibrium and the effect of interfacial viscosity at oil-water interfaces is considered. With these assumptions, we find that the importance of viscous coupling depends on the rheology of the oil-water interface. Where the interfacial shear viscosity is zero, viscous coupling leading to a dependence of oil relative permeability on oil-water viscosity ratio for viscosity ratios greater than one is important for a range of pore cross-section shapes and pore size distributions. For nonzero interfacial shear viscosity, viscous coupling is reduced. Using values reported in the literature for crude oil-brine systems, we find no viscous coupling.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 8 (1992), S. 99-131 
    ISSN: 1573-1634
    Keywords: Characteristic ; wavespeed ; shock ; expansion fan ; Rankine-Hugoniot equations ; entropy inequality ; two-phase flow ; counterflow ; saturation ; pressure ; convection ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: abstract New concepts are introduced to describe single-component two-phase flow under gravity. The phases can flow simultaneously in opposite directions (counterflow), but information travels either up or down, depending on the sign of the wavespeedC. Wavespeed, saturation and other quantities are defined on a two-sheeted surface over the mass-energy flow plane, the sheets overlapping in the counterflow region. A saturation shock is represented as an instantaneous displacement along a line of constant volume fluxJ Q in the flow plane. Most shocks are of the wetting type, that is, they leave the environment more saturated after their passage. When flow is horizontal all shocks are wetting, but it is a feature of vertical two-phase flow that for sufficiently small mass and energy flows there also exist drying shocks associated with lower final saturations.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 7 (1992), S. 223-253 
    ISSN: 1573-1634
    Keywords: Characteristic ; wavespeed ; shock ; expansion fan ; Rankine-Hugoniot equations ; entropy inequality ; two-phase flow ; saturation ; pressure ; geothermal ; convection ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract In the absence of capillarity the single-component two-phase porous medium equations have the structure of a nonlinear parabolic pressure (equivalently, temperature) diffusion equation, with derivative coupling to a nonlinear hyperbolic saturation wave equation. The mixed parabolic-hyperbolic system is capable of substaining saturation shock waves. The Rankine-Hugoniot equations show that the volume flux is continuous across such a shock. In this paper we focus on the horizontal one-dimensional flow of water and steam through a block of porous material within a geothermal reservoir. Starting from a state of steady flow we study the reaction of the system to simple changes in boundary conditions. Exact results are obtainable only numerically, but in some cases analytic approximations can be derived. When pressure diffusion occurs much faster than saturation convection, the numerical results can be described satisfactorily in terms of either saturation expansion fans, or isolated saturation shocks. At early times, pressure and saturation profiles are functionally related. At intermediate times, boundary effects become apparent. At late times, saturation convection dominates and eventually a steady-state is established. When both pressure diffusion and saturation convection occur on the same timescale, initial simple shock profiles evolve into multiple shocks, for which no theory is currently available. Finally, a parameter-free system of equations is obtained which satisfactorily represents a particular case of the exact equations.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 6 (1991), S. 519-547 
    ISSN: 1573-1634
    Keywords: Heterogeneous porous media ; two-phase flow ; numerical simulation ; finite element method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A mathematically rigorous method of homogenization is presented and used to analyze the equivalent behavior of transient flow of two incompressible fluids through heterogeneous media. Asymptotic expansions and H-convergence lead to the definition of a global or effective model of an equivalent homogeneous reservoir. Numerical computations to obtain the homogenized coefficients of the entire reservoir have been carried out via a finite element method. Numerical experiments involving the simulation of incompressible two-phase flow have been performed for each heterogeneous medium and for the homogenized medium as well as for other averaging methods. The results of the simulations are compared in terms of the transient saturation contours, production curves, and pressure distributions. Results obtained from the simulations with the homogenization method presented show good agreement with the heterogeneous simulations.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 5 (1990), S. 215-229 
    ISSN: 1573-1634
    Keywords: Coupling ; relative permeabilities ; porous media flows ; two-phase flow ; Darcy's law
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An extended formulation of Darcy's two-phase law is developed on the basis of Stokes' equations. It leads, through results borrowed from the thermodynamics of irreversible processes, to a matrix of relative permeabilities. Nondiagonal coefficients of this matrix are due to the viscous coupling exerted between fluid phases, while diagonal coefficients represent the contribution of both fluid phases to the total flow, as if they were alone. The coefficients of this matrix, contrary to standard relative permeabilities, do not depend on the boundary conditions imposed on two-phase flow in porous media, such as the flow rate. This formalism is validated by comparison with experimental results from tests of two-phase flow in a square cross-section capillary tube and in porous media. Coupling terms of the matrix are found to be nonnegligible compared to diagonal terms. Relationships between standard relative permeabilities and matrix coefficients are studied and lead to an experimental way to determine the new terms for two-phase flow in porous media.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 5 (1990), S. 97-102 
    ISSN: 1573-1634
    Keywords: Coupled transport processes ; two-phase flow ; pore space models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Here it is acknowledged that analytical descriptions of idealized two-phase flow of immiscible fluids in certain capillary pore spaces (e.g. those shaped like cylinders and cracks) actually are quite easy to derive. Such flow also can be regarded as primitive examples of coupled transport processes. As such, they may be employed to serve as models of how comparable processes probably occur in real porous media of complex pore structure. While the degree of coupling to be expected for all transport systems inherently is a question that ultimately must be answered by making experimental observations, qualitative indications also can come from model studies such as the ones presented in this paper. The main conclusion drawn from the work reported herein is that ambiguities can result whenever coupling effects arbitrarily are ignored just because direct measurements are too difficult or inconvenient to obtain.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 4 (1989), S. 319-334 
    ISSN: 1573-1634
    Keywords: Finite elements ; consolidation ; porous media ; two-phase flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper details a finite element model which describes the flow of two-phase fluid and heat within a deforming porous medium. The coupled governing equations are derived in terms of displacements, pore pressures and temperatures, and details of the time-stepping algorithm and thermodynamic considerations are also presented. Two numerical examples are included for verification.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 2 (1987), S. 383-393 
    ISSN: 1573-1634
    Keywords: Volume averaging ; deviation variable boundary conditions ; closure ; two-phase flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The derivation of the governing equations for immiscible, two-phase flow through porous media by Whitaker (Transport in Porous Media 1, 105–125 (1986)) contains an error which is corrected in the present work. The modified equations contain terms not present in the original equations, but their presence does not cause any fundamental changes from the conclusions reached in the original work. However, these extra terms may be important in computations associated with the closure problem.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 2 (1987), S. 397-420 
    ISSN: 1573-1634
    Keywords: Geothermal energy ; numerical models ; two-phase flow ; thermodynamic properties ; finite difference simulator ; hydrodynamic properties ; thermodynamic domain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
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