PERMFILE49521

• Permit No: M1999002
• IBM Index Class Name: Permit File
• Doc Name: Reference: NUCLEAR WELL LOGGING
• Media Type: D
• Archive: No

I SG NUCLEAR w'ELL LOGGING 4
(b) Clay type identification:~lot of thorium versus potassium will indica~at type
of clay is present as shown in Fig. 4.3. The thorium/potassium ratio can also be
used.
(c) Source rock potentiel of shale: A relation exists between the uranium-to-potassium
ratio and the organic carbon content. The source rock potential of shale can thus be
evaluated.
»m
Th
(GPm)
mm
~m
e4l
om
K(°f~
Fig. 4.3. -Plot of thorium versus uranium.
(After W. H. Ferrt)
4.3. DIFFUSED GAMMA-RAY LOGS
Gamma rays interact with matter in three different ways:
(a) Pairs (electron + positron) are produced if the energy of the incident GR is greater
than 1.02 MeV.
(b) Compton diffusion by the electrons occurs in the entire gamma spectrum, and this is
used in density logging. The amount of Compton diffusion is related to the number of
electrons by the unit volume which in turn is linked to the specific gravity o(the
matter.
(c) Photoelectric absorption occurs (or low-energy gamma rays. This absorption
depends on the nucleus-electron bonding energy which in turn is linked to the
atomic number Z of the nucleus. This absorption is the basis (or another log, the
Litholog.
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4.3.1. Densil
As shown in Fi
mounted on the
the gamma rays
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equation:
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where
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pm, is the den
pf is the den
~ is the por