Page 536 - Petrophysics

PETROPHYSICAL PROPERTIES 503

TABLE 8.2
POROSITY
OF VARIOUS NATURALLY FRACTURED RESERVOIRS [2 11
Field Porosity Range (“h)

Beaver Gas Field 0.05-5
Austin chalk 0.2
General statement 1
South African Karst Zone 1-2
CT scan examples 1.53-2.57
Epoxy injection examples 1.81-9.64
Monterey 0.01-1.1

TABLE 8.3
FRACTURE WIDTH AND SPACINGS OF VARIOUS NATURALLY FRACTURED
FORMATIONS [2 11
Spacing/
Field Width Range (mm) Average Frequency
Spraberry 0.33 max. 0.05 1 Few inches to a
few feet
Selected dam sites 0.051 to 0.10 4to14ft
La Paz-Mara field 6.53 max.
Small joints 0.01 to 0.10
Extension fractures 0.1 to 1.0 0.2
Major extension fractures 0.2 to 2
Monterey 0.01 3 to 36ft

oil in place in the reservoir is given by the following equation [ 101 :

where Nom and Nof are, respectively, the oil volumes trapped in the
matrix and fractures. Assuming a volumetric system, these two volumes,
expressed in STB, are calculated as follows:

where: A = surface area of the reservoir, acres
h = average reservoir thickness, ft