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Look to CM Starches to Replace Polyanionic Cellulose

Polyanionic cellulose (PAC) is a common additive to water-based drilling muds. Often used in regions with hard-rock applications, such as the Rocky Mountain range in the U.S. and Canada, PACs were primarily used because of their ability to control fluid loss, improve carrying capacity and offer inhibition properties.

However, PACs have drawbacks, particularly cost, heat tolerance and rheological limitations. Polyanionic cellulose comes at a premium price because the raw materials needed to produce it (typically wood pulp or cotton linter) are in high demand among a variety of industries. PACs also do not perform well at higher temperatures. As temperatures rise, more and more product must be added to maintain the desired properties. They also have rheological limitations in certain systems and often contribute to a higher plastic viscosity, not yield point. PACs are susceptible to divalent contaminants, too.


Advancements in Starch Technology
Due to these reasons, many companies have searched for replacements to polyanionic cellulose. During their research, many are surprised to learn of the advancements in carboxymethyl (CM) starches as a PAC replacement. They do not realize the contributions CM starches have made to rheology improvements, lubricity and fluid loss control while being more resistant to thermal degradation and bacterial attack. Carboxymethyl starches also have a synergy with xanthan gum, reducing the amount required in a system to meet pseudo plasticity objectives. As an added bonus, CM starches clean up much more easily than xanthan gum.


Multiple PAC Replacements Available.

If you are seeking PAC alternatives, Chemstar has a variety of starch-based options with stable pricing and availability. You can view our full line of Drilling solutions here, but our most popular PAC replacement is our StarPak® series, which displays a synergy with low levels of xanthan gum and bentonite clay to provide shear-thinning fluids with excellent low-end rheology. Our StarPak DP is a double derivative that offers lubricity and bio-stability, two highly sought after properties.

As we noted in a previous blog, StarDril® was developed specifically for the Canadian drilling market in areas sensitive to Canadian Microtox testing issues. It is a cost-effective and environmentally sound alternative to PAC for land spreading while drilling (LWD) operations.

Finally, our ExStar® series, while not a CM starch, does impart filtration control and enhanced rheology with thermal stability to 300o F.


Please feel free to send me an email  you are interested in learning more about Chemstar’s PAC replacement solutions.


-Bruce Hanshaw

Business Manager, Global Oil & Gas App