Page 556 - Petrophysics

PETROPHYSICAL PROPERTIES 523

Or, assuming the fracture length is equal to the length of the core sample:

(8.40b)

Where:

nf = number of fractures in fractured core sample
R, = Brine or water resistivity, Ohm-m
rof = electrical resistance of the fractured core sample, Ohm
D = Diameter of fractured core sample as shown in Figure 8.28A, cm
L = Length of fractured core sample as shown in Figure 8.28A, cm
kf = Fracture permeability, Darcy
$f = Fracture porosity, percent
wf = Fracture width or aperture, micrometer (pm)

EXAMPLE

Resistivity measurements were performed on a 100% water saturated
core sample containing 5 fractures. The following results were obtained:

r,f = 675 Ohm Rw = 0.15 Ohm-m D = 7.62 cm
L = 30.48 cm Qt = 10.3%

Calculate:

(a) Fracture width
(b) Fracture porosity
(c) Fracture Permeability
(d) Porosity partitioning coefficient and matrix porosity.

SOLUTION

(a) The fracture width or aperture is obtained from Eq. 8.40b:

106RwL lo6 x 0.15 x 30.48
-
Wf = - = 178ym
w0fD 5 x 6751 x 7.62
(b) The fracture porosity is estimated from Eq. 8.39:

0.04nfwf 0.04 x 5 x 178
-
Qf = - = 1.5%
7CD 7.627~