Table 2 Minimum and maximum threshold values of different logs to distinguish coal (modified after34,54).

From: Reservoir rock typing assessment in a coal-tight sand based heterogeneous geological formation through advanced AI methods

Logs

DEN (g/cm3)

CNL (dec)

AC (us/ft)

LLD (Ω m)

GR (API)

Minimum ranges

1.1

0.35

90

10

10

Maximum ranges

1.95

0.75

160

2000

 ~ 100*

  1. *GR varies depending upon the presence of Th or U isotope series.
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