Page 161 - Petrophysics 2E

134 PETROPHYSICS: RESERVOIR ROCK PROPERTIES

SOLUTION

(a) The Permeability of an oil-bearing core sample according to the
Wyllie and Rose correlation (Equation 3.63) is [32]:

2

The Timur correlation (Equation 3.64) gives:

Q4.4
k = 0.136-
%i
(0.24)4.4
k = 0.136 = 179mD
(30l2
The permeability obtained from the Timur equation is 25.7% higher
than that obtained from the Wyllie and Rose equation. One of
the reasons is that the Timur permeability-porosity correlation was
obtained from core samples with high permeability.
(b) The average grain size can be estimated from Equation 3.62. Solving
for the grain diameter d,, we have, for k = 133 mD:

k = 10.5 dg43.3

k

133 = 1.4m
dgt. = lC1.5(0.24)~-~

For k = 179 mD, the grain diameter is dg = 1.9 mm. Thus, accord-
ing to Table 1.7, the particles of the sandstone are very coarse and
range in diameter from 1 to 2 mm.

PERMEABILITY FROM NMR LOG

The NMR log uses a permanent magnet, a radio frequency (RF)
transmitter, and an RF receiver. The tool responds to the fluids in
the pore space and is used to measure lithology-independent effective