Abstract
Recent displacement experiments show ‘anomalously’ rapid spreading of water during imbibition into a prewet porous medium. We explain this phenomenon, calledhyperdispersion, as viscous flow along fractal pore walls in thin films of thicknessh governed by disjoining forces and capillarity. At high capillary pressure, total wetting phase saturation is the sum of thin-film and pendular stucture inventories:S w =S tf +S ps . In many cases, disjoining pressure ∏ is inversely proportional to a powerm of film thicknessh, i.e. ∏ ∞h −m , so thatS tf ∞P c −1/m. The contribution of fractal pendular structures to wetting phase saturation often obeys a power lawS ps ∞P c (3−D), whereD is the Hausdorff or fractal dimension of pore wall roughness. Hence, if wetting phase inventory is primarily pendular structures, and if thin films control the hydraulic resistance of wetting phase, the capillary dispersion coefficient obeysD c ∞S v w , where v=[3−m(4−D) ]/m(3−D). The spreading ishyperdispersive, i.e.D c (S w ) rises as wetting phase saturation approaches zero, ifm>3/(4−D),hypodispersive, i.e.D c (S 2) falls as wetting phase saturation tends to zero, ifm<3/(4−D), anddiffusion-like ifm=3/(4−D). Asymptotic analysis of the ‘capillary diffusion’ equation is presented.
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Abbreviations
- a :
-
Pre-exponential factor in power-law scaling ofD c withS w
- b :
-
Exponent in power-law scaling ofD c withS w
- B :
-
Ratio of gravitational forces to viscous forces
- D :
-
Hausdorff or fractal dimension
- D c :
-
Capillary dispersion coefficient (m2s−1)
- f(r) :
-
Pore radius probability density function
- F :
-
Fractional flow
- G :
-
Mutual permeability (m3s Kg−1)
- g :
-
Gravitational potential per unit mass (m s−)
- h :
-
Film thickness (m)
- k :
-
Absolute permeability (m2)
- k i :
-
Effective permeability of phasei(m2)
- m :
-
Power law exponent of ∏ (h) in the limit of smallh
- P c :
-
Capillary pressure,P nw −P w (Pa)
- P i :
-
Pressure in bulk phasei (Pa)
- S :
-
Wetting phase saturation
- t :
-
Time coordinate (s)
- v :
-
Net flow velocity (m s−1)
- x :
-
Spatial coordinate (m)
- z :
-
Elevation (m)
- γ :
-
Interfacial tension (N m−1)
- δ:
-
Density contrast
- λ :
-
Boltzmann transform
- Μ i :
-
Viscosity of phasei (Kg m−1 s−1)
- v :
-
Exponent in power-law scaling ofD c withS w
- ∏:
-
Disjoining pressure (Pa)
- ρ i :
-
Density of phasei (Kg m−3)
- σ 2 :
-
Variance of parent normal distribution
- Φ :
-
Porosity
- nw :
-
Nonwetting phase (oil, air)
- ps :
-
Pendular structure
- tf :
-
Thin film
- w :
-
Wetting phase (water)
References
Bacri, J.-C., Leygnac, C., and Salin, D., 1985, Evidence of capillary hyperdiffusion in two-phase fluid flows,J. Phys. Lett. (Paris) 46, L467–473.
Bacri, J.-C., Leygnac, C., and Salin, D., 1984, Study of miscible fluid flows in a porous medium by an acoustical method,J. Phys. Lett. (Paris) 45, L767.
Brooks, R. H. and Corey, A. T., 1964, Hydraulic properties of porous media, Hydrology Paper No. 3, Colorado State University, Fort Collins.
Crank J. and Henry, M. E., 1949a, Diffusion in media with variable properties: I,Trans. Faraday Soc. 45, 636–642.
Crank, J. and Henry, M. E., 1949b, Diffusion in media with variable properties: II,Trans. Faraday Soc. 45, 1119–1128.
Davis, H. T., 1989, On the fractal character of the porosity of natural sandstone,Europhys. Lett. 8, 629–632.
de Gennes, P. G., 1985, Partial filling of a fractal structure by a wetting fluid, in D. Adleret al. (eds),Physics of Disordered Materials, Plenum Press, New York, pp. 227–241.
Derjaguin, B. V. and Churaev, N. V., 1974, Structural component of disjoining pressure,J. Colloid Interface Sci. 49, 249–255.
Derjaguin, B. V. and Landau, L. D., 1941, Theory of stability of strongly charged lyophobic sols and of the adhesion of strongly charged particles in solutions of electrolytes,Acta Phys.-Chim. URSS. 14, 633–662.
Feder, J., 1988,Fractals, Plenum, New York.
Gardner, W. R. and Mayhugh, M. S., 1958, Solution and tests of the diffusion equation for the movement of water in soils,Soil Sci. Soc. Am. Proc. 22, 197–201.
Hillel, D., 1971,Soil and Water: Physical Principles and Processes, Academic Press, New York.
Jackson, R. D., 1964a, Water vapor diffusion in relatively dry soil: I. Theoretical considerations and sorption experiments,Soil Sci. Soc. Am. Proc. 27, 172–176.
Jackson, R. D., 1964b, Water Vapor diffusion in relatively dry soil: III. Steady state experiments,Soil. Sci. Soc. Am. Proc. 27, 467–470.
Katz, A. J. and Thompson, A. H., 1985, Fractal sandstone pores: Implications for conductivity and pore formation,Phys. Rev. Lett. 54, 1325–1328.
Klute, A., 1952, A numerical method for solving the flow equation for water in unsaturated materials,Soil Sci. 73, 105.
Melrose, J. C., 1988, Characterization of petroleum reservoir rocks by capillary pressure techniques, in K. K. Ungeret al. (eds.),Characterization of Porous Solids, Elsevier, Amsterdam, pp. 253–261.
Mohanty, K. K., 1981, Fluids in porous media: Two-phase distribution and flow, PhD Thesis, University of Minnesota, Minneapolis.
Novy, R. A., Toledo, P. G., Davis, H. T., and Scriven, L. E., 1989, Capillary dispersion in porous media at low wetting phase saturations,Chem. Eng. Sci. 44, 1785–1797.
Pashley, R. M., 1980, Multilayer adsorption of water on silica: An analysis of experimental results,J. Colloid Interface Sci. 78, 246–248.
Peaceman, D. W., 1977,Fundamentals of Numerical Reservoir Simulation, Elsevier-North-Holland, New York.
Philip, J. R., 1955a, Numerical solution of equations with diffusivity concentration-dependent,Trans. Faraday Soc. 51, 885–892.
Philip, J. R., 1955b, The concept of diffusion applied to soil water,Proc. Natl. Acad. Sci. India A24, 93–104.
Sahimi, M., 1984, Transport and dispersion in porous media and related aspects of petroleum recovery, PhD Thesis, University of Minnesota, Minneapolis.
Toledo, P. G., Novy, R. A., Davis, H. T., and Scriven, L. E., 1990a, Hydraulic conductivity of porous media at low water content,Soil Sci. Soc. Am. J. 54, 673–679.
Toledo, P. G., Novy, R. A., Davis, H. T., and Scriven, L. E., 1990b, On the transport properties of porous media at low water content, in M. Th. van Genuchten (ed.),Indirect Methods for Estimating the Hydraulic Properties of Unsaturated Soils, Riverside, California.
Ward, J. S. and Morrow, N. R., 1987, Capillary pressure and gas relative permeabilities of low-permeability sandstone,Soc. Pet. Eng. Form. Eval. 1, 93–104.
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Toledo, P.G., Ted Davis, H. & Scriven, L.E. Capillary hyperdisperson of wetting liquids in fractal porous media. Transp Porous Med 10, 81–94 (1993). https://doi.org/10.1007/BF00617512
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DOI: https://doi.org/10.1007/BF00617512