Formation Evaluation Through Casing - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 157

Capture Cross Sections

The capture cross section of a formation depends on the elements that make up the
formation and their relative abundance. ʣ values vary over a wide range. The cap-
ture cross sections for thermal neutrons are listed in Table 11.1 for a number of
elements and in Table 11.2 for various compounds found in rocks.

Table 11.1 Capture cross
sections of elements

Element ʣ (cu)

Common elements
Chlorine 570

Hydrogen 200

Nitrogen 83

Potassium 32

Iron 28

Sodium 14

Sulfur 9.8

Calcium 6.6

Aluminum 5.4

Phosphorus 3.9

Silicon 3.4

Magnesium 1.7

Carbon 0.16

Oxygen 0.01

Rare elements
Boron 45,000

Cadmium 18,000

Lithium 6,200

Mercury 1,100

Manganese 150