Page 236 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 212

[ ] Well Programming
2.5.5

Polymers can be classified according to the ionic charge they carry.
There are three main types of polymers in this classification:

Anionic polymers. These carry a net anionic (negative) charge
Cationic polymers. These carry a net cationic (positive) charge
Nonionic polymers. These carry no net charge

There is a fourth group known as amphoteric polymers. The
charge nature will vary depending on the environment in which they
exist. They are not commonly used in drilling muds as “dry powder”
polymers, but they may be present as surfactants.
Polymers can also be classified according to their origin and man-
ufacturer. First, there are natural polymers. These are derived from veg-
etable material and they are used in their extracted form without any
alteration. Guar gum would be an example of a natural polymer. The
guar polymer is extracted from the soybean. Cornstarch or raw potato
starch would be another example. Second, there is the class of poly-
mers known as semisynthetic polymers. These are natural polymers,
often derivatives of cellulose, which have been altered by chemical
groups substituted onto their molecules or processed to undergo fur-
ther polymerization.
Finally, there is the group known as synthetic polymers. These are
polymers that have been synthesized from chemical derivatives such as
acrylic acids, acrylates, various acetates, etc.
Polymer usage. Polymers may be classified by their usage. Listed
below are some uses of polymers in drilling muds.
Flocculants. High molecular weight synthetic polymers whose mol-
ecules are long enough to cause clays and ultra fine drilled solids to be
joined together.
Deflocculants (or thinners). These negatively charged polymers
work by adsorbing onto clays to negate positive charges and provide a
net negative charge to the clay platelet. Examples are lignosulfonates,
lignins, polyphosphates, and low molecular weight polyacrylates.
Viscosifiers. Normally these are high molecular weight polymers
that in water do not “unravel” very well because their polymer chains
are so big. In water, there is a strong interaction between the polymer
chains that demonstrates itself as viscosity. Shear decreases these poly-
mer interactions and thus a polymer can provide a viscosity that can be

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