Page 77 - Percolation Models for Transport in Porous Media With

4.3 MIXED WETTABILITY 69

Figure 19: Curves for the calculation of the phase permeabilities for a - flow of
the Binghamian plastic (code: r'.,Jro); b- visco-plastic and dilatant liquids (code:
n)

The results ofthe calculation of kt(S) for the Binghamian plastic are presented
in fig.19, a. As Tp goes up, the phase permeabilities of both the displacing and the
displaced fluid drop sharply; therefore, the limiting shear during the extraction of
anomalous oils should be made as small as possible.
The obtained results qualitatively agree with the experimental data [65] and
with the results of the numerical computations [8] based on the network model,
carried out in the development [59] {the agreement is satisfactory). In the latter
case, the only non-Newtonian (Binghamian) fluid is oil (water is Newtonian), and
it is for oil that the typical transformation of the k~ ( S) curve like the one shown
in fig. 19, a, is observed.
The plots of the relations kf(S} for visco-plastic and dilatant fluids are pre-
sented in fig.19, b. The case of n = 1 corresponds to the Newtonian fluids; n = 2,
to the dilatant fluids; n = 1/2, to the pseudo-plastic fluids. When the exponent n
in (4.23} changes, all the more at the transfer from one fluid type to another (from
n < 1 ton> 1), the phase permeabilities change notably. This phenomenon can
be widely used in various applications.

4.3 Phase Permeabilities of a Medium with Mixed
Wettability

In actual media capillaries often differ not only in size, but also in properties of
wettability of their surfaces. The effects of mixed wettability of a porous medium
on the relative phase permeabilities of fluids flowing through it has been studied
earlier in [9] by means of the numerical simulation of the capillary displacement