Page 166 - Reservoir Formation Damage

148 Reservoir Formation Damage

Electrostatic Double-Layer Force. These forces are created due to the
ionic conditions measured by pH and ionic strength. When the particle
and grain surfaces carry the electrostatic charges of the same sign, they
repel each other. The repulsive force is expressed by (Ives, 1985):

(8-10)
+ Qxp[-kd(s-2)]

where s is the dimensionless separation distance expressed as the ratio
of the radial separation distance divided by the particle radius (d/2), k is
the Debye reciprocal double-layer thickness, and d is the particle diameter.
When the ionic strength is higher, then the double-layer thickness is
smaller, and hence k is larger.

Born Repulsion Force. This force is generated as a result of the over-
lapping of the election clouds (Wojtanowicz et al., 1987, 1988).

Rate Equations for Participate
Processes in Porous Matrix
Ohen and Civan (1993) classified the indigenous particles that are
exposed to solution in the pore space in two groups: lump of total
expansive (swelling, that is, total authigenic clay that is smectitic) and
lump of total nonexpansive (nonswelling) particles, because of the differ-
ence of their rates of mobilization and sweepage from the pore surface.
They considered that the particles in the flowing suspension are made of
a combination of the indigenous particles of porous media entrained by
the flowing suspension and the external particles introduced to the porous
media via the injection of external fluids. They considered that the
particles of the flowing suspension can be redeposited and reentrained
during their migration through porous media and the rates of mobilization
of the redeposited particles should obey a different order of magnitude than
the indigenous particles of the porous media. Further, they assumed that the
deposition of the suspended particles over the indigenous particles of the
porous media blocks the indigenous particles and limits their contact and
interaction with the flowing suspension in the pore space. They considered
that the swelling clays of the porous media can absorb water and swell to
reduce the porosity until they are mobilized by the flowing suspension.
The rate at which the various paniculate processes occur in porous
media can be expressed by empirical equations. These equations can also
be considered as the particulate material balance equations for the porous
matrix. Here they are written as volume balance of particles.