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1.3 Pore-scale modeling approach
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features of the pore geometry of porous medium. The primary topological feature
of a pore system is the coordination number distribution. Physical flow
and solute transport properties on the other hand require, in addition, exact or
approximate equations of motion. Often this involves steady or unsteady state
transport of physical quantities such as mass, energy, charge or momentum.
Pore-network models are commonly based on an idealized description of pore
spaces [Scheidegger, 1957, De Jong, 1958]. However, in order to mimic realistic
porous media processes, network models should reproduce the main morphological
and topological features of real porous media. This should include pore-size
distribution, and coordination number and connectivity [Helba et al., 1992, Hilfer
et al., 1997, Øren et al., 1998b, Ioannidis and Chatzis, 1993a, Sok et al.,
2002, Arns et al., 2004]. In the present study, we have used a Multi-Directional
Pore Network (MDPN) for representing a porous medium. One of the main
features of our network is that pore throats can be oriented not only in the
three principal directions, but in 13 different directions, allowing a maximum
coordination number of 26, as shown in Figure 1.1.
Figure 1.1: Schematic of a 26-connected network. Numbers inside
the squares show tube directions and others are pore body numbers
[Raoof and Hassanizadeh, 2009].
Flow and transport processes are simulated at the pore scale in detail by explicitly
modeling the interfaces and mass exchange at surfaces. The solution of the
pore network model provides local concentrations and enables computation of
the relationship between concentrations and reaction rates at the macro scale
to concentrations and reaction rates at the scale of individual pores, a scale at
which reaction processes are well defined [Li et al., 2007a,b]. Comparing the
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