Page 90 - Basic Well Log Analysis for Geologist

POROSITY LOGS

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Figure 28. Example of a bulk density log with a gamma ray log and caliper. and formation factor curve (*). This log is presented
to show you the scales of a density log, and is used in picking values for Figure 29.

Track #1—This track includes both the gamma ray and caliper logs. Note that both scales read left-to-right: the gamma
ray values range from 0 to 100 APT gamma ray units. and the caliper measures the borehole size from 6 to 16
inches.
Tracks #2 and #3—The bulk density curve (p,). correction curve (A,,), and formation factor curve (F) are recorded in this
track. The correction (A,), formation factor, and the bulk density scales increase in value from left to right,

The bulk density (p,) scale ranges in value from 2.0 gni/cc to 3.0 gnice and is represented by a solid line. The
density log correction curve (A,) ranges in value from —0.05 gm/ce to +0.45 gm/ce in increments of 0.05 gni/ee,
but only uses the left half of the log track. The formation factor curve (F) ranges in value from 1 to 10,000
(discussed later) and is represented by a dashed line.
At the sample depth used in Figure 29 (9,310 ft) read a bulk density value (p,) of 2.56 gm/cc.

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