BAKER HUGHES - Drilling Fluids Reference Manual

Water-base Drilling Fluids
Chapter 3
Water-based drilling fluids, regardless of the name assigned to them, usually
contain clays, water soluble chemicals (including salts), a pH control additive
(hydroxyl source), and one or more organic polymers, surfactants, and
deflocculants.
Introduction
In order for drilling fluid engineering to be a science and not an art, a basic understanding of the
chemistry involved is required. This chapter attempts to provide the chemical background to the
reactions that take place in the fluid.
By adoption of this approach the engineer will be well equipped to deal with variations in the
fluid properties which may occur from time to time. If the basic chemical concepts are well
understood, then the causes of any problems can be better identified and dealt with
The Structure of Matter
The properties and reactions of materials can be related to the basic structures of the atoms and
molecules of which they are formed. The difference between water and diesel, bentonite and
sand, and so on, arises from their physical and chemical properties which are best understood in
these terms
Elements and Compounds
An element is a chemically unique substance which cannot be split up into a simpler chemical
form by chemical means. The names of the various elements are usually written as abbreviations
to simplify chemical notation. A full list of elements and their symbols is given in Table 3-1.
Elements can combine together to form compounds. A compound has different chemical and
physical properties than those of the simple mixture of elements from which the compound is
formed. Thus hydrogen and oxygen are both gases and remain gases when they are mixed
together. However, if they are chemically combined, they form water, which is a liquid. When
elements combine together, they do so in a fixed ratio by weight, which always remains constant
for one particular compound.
Atoms and Molecules
An atom is the smallest particle of an element which can exist and still retain the same chemical
properties of that element. Atoms are the basic building bricks of matter from which all things
are constructed. They are the smallest units of matter which can undergo chemical change.
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 3-1