Page 540 - Petrophysics

PETROPHYSICAL PROPERTIES 507

1000

.-
v) 800
Q
F“
2 600
v)
F
a
400

200

0
0 100 200 300
Volume of water injected, cc
Figure 8.11. Locke and Bliss Method for Estimating the Pore Space of Fractures.

The term v is commonly referred to as the “porosity partitioning
coefjcient.” This coefficient represents the apportioning of total porosity
(@) between the matrix (intergranular) porosity, @m, and secondary
pores (vugs, fractures, joints, and fissures), @f.
The value of v ranges between zero and unity for dual porosity systems.
For total porosity equal to matrix porosity (absence of fracture porosity),
v = 0. For total porosity equal to fracture porosity, v = 1. This coefficient
can be estimated from core analysis using the Locke and Bliss method,
pressure analysis, and well logging data. By assuming that the fractures
and matrix are connected in parallel, as shown in Figure 8.20, Pirson
suggested the following equations for short and long normal or induction
tools [25]. If the drilling fluid used is non-conductive, the following
correlations can be used to estimate the porosity partitioning coefficient
and fracture intensity index:

(a) Short Normal

(8. loa)

(8.10b)