Page 86 - Basic Well Log Analysis for Geologist

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POROSITY LOGS

Figure 26. Example sonic log with gamma ray log and caliper. This example is shown to display the scales of a sonic log, and to
be used in picking an interval transit tume (At) value for Figure 27.

Track #1—This track includes both the gamma ray and caliper curves. Note that the gamma ray scale reads from 0 to 100
API gamma ray units, increasing from left-to-right in increments of 10 untts. The gamma ray scale is represented
by a solid line.

The caliper scale ranges from 6 to 16 inches, from left-to-right in one-inch increments, and is represented by a
dashed line.
Tracks #2 and #3—Both the interval transit time (Av) scale and the porosity scale are shown in this track. Sonic log
interval transit time (At) is represented by a solid line, on a scale ranging from 40 to 80 wsce/ft increasing from
right-to-left.
The sonic porosity measurement (limestone matrix) is shown by a dashed line, on a scale ranging from ~ 10% to
+30% porosity increasing from right-to-left.

At the sample depth used in Figure 27 (9.310 ft), read a sonic log interval transit time (At) value of 63 psec/tft.

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