Deviation from Archie's law in partially saturated porous media: Wetting film versus disconnectedness of the conducting phase.
Phys Rev E Stat Nonlin Soft Matter Phys
; 79(3 Pt 1): 031127, 2009 Mar.
Article
de En
| MEDLINE
| ID: mdl-19391922
ABSTRACT
We experimentally study the electrical transport in partially water-saturated pore network. The porous medium under investigation is a Fontainebleau sandstone, characterized by x-ray tomography. We show the existence of two electrical conductivity regimes. At high water saturation, the electric resistivity follows a well-known Archie law. Below a water saturation S_{w} approximately 0.2 , a strong negative deviation from this Archie law is observed. We attribute this transition to the existence of "a thick liquid film," assuring the ionic conduction in the low saturation regime. A numerical simulation is proposed to confirm this scenario. Two possible protocols are used to distribute the brine phase in the pore network of a three-dimensional microtomography image. The first one is based on a minimization of the interfacial energy. The second takes into account a quasistatic capillary displacement. The classical random-walk algorithm is used to compute the electric conductivity at various water saturations. Without the "thick film," both of the two fluid-placing protocols show a disconnectedness transition of the brine phase when S_{w}<0.2 . Adding this "film" to solid surface, the electrical continuity is maintained. The bending down trend is correctly reproduced, showing that in this range, the electric response cannot be described by a power law as usual.
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Collection:
01-internacional
Base de données:
MEDLINE
Langue:
En
Journal:
Phys Rev E Stat Nonlin Soft Matter Phys
Sujet du journal:
BIOFISICA
/
FISIOLOGIA
Année:
2009
Type de document:
Article
Pays d'affiliation:
France