Page 260 - Reservoir Formation Damage

240 Reservoir Formation Damage

Solid matrix

nS, Non-wetting wS, Wetting
surface surface
\

Pore Pore
body throat

Figure 11-1. Multi-phase system in porous media.

experimental investigations, Muecke (1979) has observed that particles
tend to remain in the phases that can wet them. Ku and Henry, Jr. (1987)
have shown that intermediately wet particles accumulate at the interface
of the wetting and nonwetting phases, because they are most stable there.
Therefore, in the following formulation, an interface region contain-
ing the intermediately wet particles is perceived to exist in between
the wetting and nonwetting phases as schematically indicated in Figure
11-1. Further, it is reasonable to consider that the wettability of some
particles may be altered by various processes, such as asphaltene, paraffin,
and inorganic precipitation or by other mechanisms such as the turbulence
created by rapid flow in the near-wellbore region. Consequently, these
altered particles should tend to migrate into the phases that wet them as
inferred by the experimental studies of Ku and Henry, Jr. (1979).
In addition to the particles, the various phases may contain a number
of dissolved species. The salt content of the aqueous phase is particularly
important, because it can lead to conditions for colloidally induced release
of clay particles when its salt concentration is below a critical salt
concentration (Khilar and Fogler, 1983).
For convenience in formulation, the locations for particles retention can
be classified in three categories: (1) the wetting pore surface, (2) the
nonwetting pore surface, and (3) the pore space behind the plugging pore