BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
Isotopes
These different forms of the same element are called isotopes and are denoted by writing the
atomic weight as a superscript. Thus, carbon has three isotopes; C 12 , C 13 , and C 14 .
Hydrogen also has three isotopes, with either zero, one or two neutrons in the nucleus. The most
common form is H 1 (99.985%). The other two isotopes have been given special names (the only
isotopes to have been so honored). H 2 is known as deuterium (D) and H 3 is known as tritium (T).
Tritium is radioactive, that is, it has an unstable nucleus which can emit an electron and thus
change the tritium into a stable isotope of helium He 3 . This fact makes tritium easy to detect and
for this reason titrated water (that is water to which T 2 O gas been added) is used as a tracer in
formation analysis.
Many other isotopes are also radioactive. For example, the heavy isotope of potassium, K 40 emits
high energy radiation known as gamma rays. This gamma radiation is utilized in well logging. A
gamma ray log shows high concentrations of potassium bearing minerals, such as micas, in a
shale, or carnallite in a salt section.
Molecular Weight
The molecular weight of a compound is simply the sum of the atomic weights of the atoms it
contains. For example, water, H 2 O, has molecular weight 18 (atomic weight of hydrogen = 1,
atomic weight of oxygen = 16).
The Periodic Table
Table 3 - 2 shows the elements grouped together in a special way known as the periodic table.
The elements are shown in order of increasing atomic number and are arranged in a series of
column (groups IA – VIIA). This reflects an earlier classification based on the chemical
properties of the various elements. In the modern form, elements in the same group are
chemically related and show regular trends in chemical properties. Thus the chemical nature of
an element is in some way related to its atomic number. This relationship involves the
configuration of the electrons which orbit the nucleus where the number of electrons is
determined by the atomic number.
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 3-5