Page 200 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Formation Evaluation 169

0 10 20 30 40
$sN~~~~, Porosity Index (pu)
Neutron
(Apparent Limestone Porosity)
Figure 5-96. Chart for finding porosity and matrix composition from an
FDC-SNP log combination in salt water [199].

3. Stationary display mode-a signal-stacking mode where eight signals are
stacked from each of six polarization times to obtain precise T,, T,, and
FFI values.
FFI readings yield porosity that is filled with moveable fluid and is related
to irreducible water saturation (Si,). Addition of paramagnetic ions to the mud
filtrate will disrupt the water portion of the signal and residual oil saturation
(So,) can be determined.
Desbrandes [212] summarized the following uses for the NML:
1. Measuring free fluid volume in the pores ($,)
2. Evaluating permeability by comparing 41~ with $= (total porosity from a
neutron-density log combination).