download pdf version of PhD book - Universiteit Utrecht

5. Pore-Network Modeling of Two-Phase Flow
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Probability
0.2
0.15
0.1
0.05
0
1 3 5 7 9 11 13 15
Coordination number
(a)
(b)
Figure 5.2: The coordination number distribution and a representative subdomain
of MDPN. The mean coordination number is equal to 6.0.
ditions, a given pore body or pore throat can be invaded and filled mostly by
the non-wetting phase, forcing the wetting phase to flow only along the edges.
Figure (5.3) shows a schematic example of two pore bodies connected to each
other by a pore throat of triangular cross section. Under such conditions, pore
throats are no longer necessarily the narrowest constriction along the flow path.
In fact, resistance to the flow within the edges of pore bodies may be comparable
to, or even larger than, the resistance to flow within the pore throats.
Thus, it is more realistic to consider conductance, and calculate fluxes, within
the pore bodies as well as pore throats. This lower conductivity of a pore body
can also reduce the connectivity among saturated pore throats connected to a
drained pore body (such as pore throats number 2, 3, 4 in Figure 5.3b), and
thus reduce their effective conductance although they are still saturated.
Figure 5.3: (a) Example of two drained pore-bodies connected to each other by
a drained pore throat with triangular cross section, and (b) a pore body which is
invaded by non-wetting phase, through one of its throats, and as a result reduces
the connectivity of the neighboring saturated pore throats.
100