Page 581 - Petrophysics

548 PETROPHYSICS: RESERVOIR ROCK PROPERTIES

Substituting the values of km, kf, and Qf into Equation 8.83 yields
approximately the same value of the effective permeability obtained
from well testing, i.e.

k * k, + @fkf = 0.15 + 0.0019 x 41,216 = 79.4 mD

(c) The fracture width or aperture may be estimated from Eq. 8.84

,
41,216
= 187 microns = 0.187 mm
33 x 0.25 x 0.1419

The side length Xm of the cubic block is calculated from Equation
8.73b:

This interpretation assumes that (a) the change in matrix compress-
ibility and porosity of this naturally fractured reservoir is negligible
and (b) the Warren and Root sugarcube model is applicable.

PROBLEMS

1. What are the major factors in the creation of natural fractures in the
reservoir rock?
2. Discuss (a) the geological classification and (b) the engineering
classification of natural fractures. What are these classifications based
on?

3. What are the major indicators of natural fractures?
4. Name the most prolilic naturally fractured oilfields of the world.
5. What are the major petrophysical characteristics of the natural
fractures. How do these characteristics affect the flow of fluids
through the fractures?
6. Name the most common techniques used to characterize natural
fractures in petroleum bearing rocks.
7. What are the two main parameters involved in the Warren and Root
sugar cube model? Discuss their significance and physical meaning.