Page 91 - Reservoir Formation Damage

74 Reservoir Formation Damage

CcosG
P c
(4-10)
<r,cose,
for which Kl§ can be estimated using one of the methods presented in
Chapter 5, such as by the Carman-Kozeny equation.
Ajufo et al. (1993) have demonstrated that the capillary pressure data
is sensitive to overburden pressure. In poorly sorted and cemented
formations, the effect of overburden may create an irreversible decay of
the formation integrity.
Frequently, the capillary pressure and relative permeability data are
correlated by Corey type power law empirical expressions of the nor-
malized saturation given, respectively, by (Mohanty et al., 1995):

(4-11)

and
(4-12)

where G jo is the interfacial tension of the j th fluid phase with oil, k^ is
the permeability at the end-point saturation of the j th phase, bj and « ;
are some correlation exponents, and ~Sj is the normalized saturation of
the j th phase defined as:

(4-13)

Chang et al. (1997) have resorted to Sigmund and McCaffery (1979)
type formulae to represent relative permeabilities, which can be general-
ized as:

(4-14)

where ra ; and a,- are some empirical parameters. Chang et al. (1997) have
used the following expression to represent the capillary pressure function:

where F is a scaling factor for the capillary pressure and (3 ; is an empir-
ical parameter.