Page 100 - Basic Well Log Analysis for Geologist

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POROSITY LOGS

Figure 33. © Chart for correcting Neutron-Density Log porosities for lithology where treshwater-based drilling mud is used (where
> 3 Ry).
Rur mit -
Courtesy. Schlumberger Well Services.
Copyright 1972, Schlumberger.
Given: p; = 1.0 gm/ce (suggested fluid density of fresh muds; see text under the heading: Density Logs). dy = 24 %.
and bp = 9% at a depth of 9,310 ft (from log; see Fig. 32).

Procedure:
1. Locate the neutron porosity value (@y) on the bottom scale (24%) and find the density porosity value (dp) on
the right-hand scale (9%).
lo Follow the values until they intersect on the chart. [n this example, the values meet on the lithology curve for
dolomite, and the intersection shows a true porosity value of 16.5%.