Page 179 - Petrophysics 2E

152 PETROPHYSICS: RESERVOIR ROCK PROPERTIES

irreducible water saturation is:

(3.99)

Substituting Equation 3.99 in Equation 3.97 and simplifying yields:
kv = 4.012 X 103@,3.728 F) (3.100)
(
1 - swi
2.4855

Equation 3.100 can be used to develop a vertical permeability profile in
the well, using the Swi and + from logs in clean sandstone rocks.

Shaly Sandstone Formations
Permeability in shaly heterogeneous formations is extremely
influenced by the nature of shale distribution in the rock. Shale
exists in dispersed and laminated form. Overall reservoir quality in
heterogeneous sandstones is controlled by diagenesis, dissolution of
feIdspars and carbonate, crystal feeding, mineralogical redistribution
of clay, and various cementation processes. Tiab and Zahaf related
vertical permeability to the mean hydraulic radius [46]. They defined
three general forms of correlation between vertical and horizontal
permeability as follows:

(a) Vertical permeability as a function of hydraulic mean radius:
kv = Al ( (3.101)

(b) Vertical permeability as a function of clay content:

(3.102)

(c) Vertical permeability as a function of mean grain size:

(3.103)

where AI, A2, A3, B1, B2, and B3 are coefficients and have to be
determined for specific formation.