Chapter 15. pdf

partial concentration of hydrogens per unit mass by the density of the material, 
(C
H
)
vol
= 
ρ
b
×
(C
H
)
mass
.
Hence, the partial concentration of hydrogens per unit volume 
(C
H
)
vol
= 
ρ
bwater
/9 = 1/9, because the
density of pure water is 1.000 g/cm
3
.
Now, the 
Hydrogen Index
of a material is defined as the partial concentration of hydrogens per unit
volume 
relative to water
. So, if the hydrogen index of water is constrained by the definition to be
unity, and water has a partial concentration of hydrogens per unit volume of 1/9, the hydrogen index of
a material 
is
(15.5)
where:
A
H
= the atomic mass of hydrogen atoms in the material
A
i
= the atomic mass of non-hydrogen element 
i
γ
+
⇒
+
H
n
H
2
1
1
0
1
1
γ
+
⇒
+
Cl
n
Cl
36
17
1
0
35
17
b
H
H
i
i
i
H
H
A
n
A
n
A
n
HI
ρ
+
=
∑
9
( )
H
H
i
i
i
H
H
mass
H
A
n
A
n
A
n
C
+
=
∑

---

Petrophysics MSc Course Notes The Neutron Log
Dr. Paul Glover Page 154
n
H
= the number of hydrogen atoms in a molecule of the material
n
i
= the number of non-hydrogen atoms of element 
i
in a molecule of the material
Note
:
 i 
is summed over every non-hydrogen element in the material.
Table 15.1 shows Eq. (15.5) in practice for a few minerals and fluids commonly found in reservoirs.