Page 102 - Basic Well Log Analysis for Geologist

POROSITY LOGS

Figure 34. Chart for correcting Neutron-Density Log porosities for lithology where saltwater-based drilling mud is used (where
Runt = Ry).
Courtesy, Schlumberger Well Services.
Copyright 1972, Schlumberger.
Given: p; = 1.1 gin/cc (suggested fluid density of salt muds; see text under the heading: Density Logs). gy = 24%, and
dp = 9% at a depth of 9,310 ft (from log; Fig. 32).

Procedure:
1. Locate the neutron porosity value (fy) on the bottom scale (24%), and find the density porosity value (¢bp) on
the right-hand scale (9%).
2. Follow the values until they intersect on the chart. In this example. the values meet at a point just off the
lithology curve for dolomite, and the intersection shows a true porosity value of 17%.

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