polymers chemistry

7/28/2019 Polymers Chemistry

1/26

Pol mer Chemistr


2/26

P o l y m e r C h e m i s t r y

Introduction

A polymer is a large molecule composed of a relatively small

molecules called monomers bonded together.

The molecular weight of polymers range from a few thousand to

several million molecular wei ht units.

Polymers can have thousands of repeating units.

The lower molecular weight polymers serve as deflocculants;

,

and flocculants.


3/26


4/26


Clay polymer interactions:

Depends on a number of factors:

Molecular wei ht

A high molecular weight material, such as a synthetic polyacrylate

will have a chain len th lar er the cla articles.

It is possible for one molecule to adsorb onto more than one

particles then acts as flocculants.

particules, then are defloccumlated.


5/26


Adsorption onto the clay

Generally, negatively charged polymers can adsorb on cationic sites

generated on the edges.

Most polymer used in drilling fluids tends to of this type.


6/26


Charges on Polymer Molecules

Drilling fluid polymers may carry electrostatic charges.

character.

Drilling fluid polymers may be categorized as: Nonionic, Anionic,

Cationic

Drilling fluid polymers are usually anionic or nonionic since cationic

.

The solubility of these poly- electrolytes will be affected by the

chemical makeup of the drilling fluid, pH, salts and presence of

divalent cations, etc.


7/26


Polymer Types

Each type of polymer has its own characteristics in terms of how it

functions in a particular type of drilling fluid.

Polyacrylate, Polyacrylamide, and PHPA (Synthetic)

These polymers are referred to as PHPA, (partially hydrolyzed

polyacrylamide), and are used as clay extenders, flocculants, and

encapsulating colloids.


8/26


Cellulose Derivatives

The cellulose molecule is modified by reacting with an acid, then an

oxidizing group, and then, an anionic radical is attached to theex s ng y roxy group.

Carbox meth lcellulose CMC

Low viscosity types are used to lower fluid loss in fresh water,

bentonite-based systems, and in saline conditions up to saturation.

The molecule may exhibit deflocculation effects especially in

flocculated systems, as it has a low molecular size and increases the

net negative charge on the clay particles.

More tolerance to salts and cation contamination.


9/26


High viscosity types are used to develop shear thinning

characteristics in water-based fluids.

Thermal degradation of CMC begins to accelerate rapidly atempera ures a ove .

The anionic CMC molecules are susce tible to form insoluble

complexes with polyvalent cations such as calcium or aluminum.

CMC can be used in lime-based systems if the calcium level is

reduced to below 500 mg/l.

The high viscosity grades of PAC posses inhibitive properties when

polymer on the solids.


10/26


Polyanionic Cellulose (PAC)

The PAC materials generally are more expensive than CMC due to

higher processing costs, but show a greater tolerance to hardnessan c or es. eg ns o erma y egra e a .

H drox eth lcellulose HEC

It is non-ionic so its dimensions do not change in the presence of

electrolytes, making it relatively stable in most moderate, basic

environments.

HEC has a tendency to foam when mixing.

strengths. It is susceptible to degradation through shear or heat and

has a maximum thermal stabilit of about 225F.


11/26


12/26


Guar Gum

Guar Gum is a natural, essentially non-ionic polymer that has an

excellent application as a viscofier for spud-in fluids and as aviscosifier in waters ranging from fresh to saturated salt (NaCl).

.

g eve s o ar ness an a a n y w s ow or even e m na e e

hydration process and can cause a significant decrease in viscosity.

Guar has a maximum thermal stability of about 200F and a biocide

is necessary to retard fermentation.

Guars have greater application to workover/completion operations.


13/26


Xanthan Gum

Xanthan Gum (XC polymer), is an anionic, water-soluble

polysaccharide biopolymer and classified as a natural polymer.

It has been used as a viscofier and suspending agent in fresh or salt-

water solutions.

The polymer also functions as a fluid loss control agent in that its

molecular size contributes to a filter cake plugging effect.

applications, begins to degrade thermally at temperatures of about

Xanthan Gum is the only polymer that provides thixotropy.


14/26


Polymer Uses

Viscosity

Bentonite Extension

e occu a on

Filtration Control

Surfactant

Viscosity

These are high molecular weight polymers, usually branched, and

water soluble.

scos y s ue o n erac ons e ween: po ymer mo ecu es an

water, (2) polymers themselves, and (3) polymers and solids.


15/26


Bentonite Extension

The bentonite extenders work by cross-linking bentonite particles to

increase the physical interaction between particles.

These polymers are termed extenders. They improve the suspension

and carr in abilities of a el s stem without the further addition of

solid particles.


16/26


Flocculation

Flocculants are high molecular weight, long chain, anionic molecules

which bridge between individual solids causing them to form anaggrega e.

Pol mers flocculate solid articles b linkin them into lar e

agglomerates.

If the mass of linked particles becomes great enough, gravity causes

them to drop out of suspension.


17/26


Deflocculation

These products are always anionic and of low molecular weight.

Anionic ol mers act as deflocculant b absorbin onto the ositive

edge sites of clay plates and neutralizing positives charges and

creatin an overall ne ative char e.

were completely anionic.

These polymers are sensitive to divalent cations and are less

effective when hardness exceeds about 400 mg/l.


18/26


Filtration Control

Starches, CMCs, PACs, and hydrolyzed polyacrylates are effective

filtration control agents.

Filtration control may be provided by:

A deflocculated filter cake, will pack down to form a thinner, more

impermeable filter cake such as low viscosity CMC or lignosulfonate.

Anionic polymers control filtration by viscosifying the water phase

.

Polymers, which contribute to this effect, are in the high molecular

-

viscosity Cellulose polymers.


19/26


Colloidal particles that can compress and deform to plug the pore in

the filter cake.

For this process to occur, the polymer must not be completely soluble

suc e s arc , some asp a er va ves an gn n er va ves.


20/26


Anionic polymers promote the dissociation or deflocculation of

suspended solids.

The anionic charge density and molecular weight of the polymer

c a es s e ec veness as a e occu an .

Li nosulfonates low molecular wei ht Cellulose derivatives and

Polyacrylates are the most effective.


21/26


Shale Stabilization

The term shale stabilization usually refers to a mechanism which

retards the water adsorption and the subsequent swelling clays.

Shale stabilization is provided through polymer attachment to the

ositivel char ed sites on the ed e of cla articles in shales.

This attachment minimizes water invasion into the clay particle and

reduces hydration and dispersion.

and potassium-based muds for added inhibition.


22/26


Theories suggests that:

Hydrogen bonding occurs between the polymer and the water-wet

surface of the clay.

Possible to stablish covalent bonds between the polymer molecule

and the uartz matrix t ical of most cla formations.


23/26


Surfactants

They are sometimes called surface-active agents.

ey usua y ower ng e ens on a e po n o con ac e ween

two immiscible fluids or between the fluid and solids.

The polar group is soluble in water, and is termed hydrophilic, water

.

The other end is non-polar and seeks non-polar substances,hydrophobic or water hating group.


24/26


Summary of Relationship Between Function of a Polymer in a Drilling

Fluid and its General Structure


25/26


Types and funnctions of polymers in drilling fluids


26/26


Types and functions of polymers in drilling fluids

polymers chemistry

Documents