l' abaque de orosité

1. Porosity
Schlumberger
3-10
Por
Thermal Neutron Porosity Equivalence Curves
CNL* Compensated Neutron Log; TNPH and NPHI porosity logs
Por-13b
40
30
20
10
0
0 10 20 30 40
φCNLcor, apparent limestone neutron porosity (p.u.)
φ,trueporosityforindicatedmatrixmaterial
Q
uartz
sandstone
C
a
lcite
(lim
estone)
Dolom
ite
Formation salinity
TNPH
NPHI
0 kppm
250 kppm
*Mark of Schlumberger
© Schlumberger
Chart Por-13b can be used in the same way as Chart Por-13a,
on the previous page, to convert CNL porosity logs (TNPH or
NPHI) from one lithology to another. If a log is recorded in lime-
stone porosity units in a pure quartz sandstone formation, the
true porosity can be derived.
Example: Quartz sandstone formation
TNPH = 18 p.u. (apparent limestone porosity)
Formation salinity = 250 kppm
giving True porosity in sandstone = 24 p.u.