Effect of ionic strength on solution and drilling fluid properties of ionic polysaccharides: A comparative study between Na-carboxymethylcellulose and Na-kappa-carrageenan responses

Natural polymers are widely used in different industries, mainly due to their hydrophilic features, which make it possible to solubilize them in water or absorb a large amount of it. Polysaccharides are the most widely used hydrophilic polymers, mainly because of their non-toxicity, biodegradability, compliance with environmental regulations and thickening behaviour in water. Knowledge of polymer performance in different aqueous media is essential to ensure optimal use in a desired application. In this study, the stability of sodium kappa-carrageenan and sodium carboxymethylcellulose stability was investigated in saline and basic aqueous media, as well as their applicability in drilling fluids. The ionic strength effects of the aqueous media containing Na+, Mg2+ and Ca2+ on the rheological properties of the polymer solutions were evaluated by varying the salt concentration, pH and temperature. The rheological properties and drilling fluid filtrate volume were evaluated by varying salt concentration and pH. The kappa-carrageenan solutions and drilling fluids were scarcely influenced by ion addition, at pH 7 to 10, even at higher salt concentrations, but highly influenced at pH > 11. On the other hand, carboxymethylcellulose solutions and their drilling fluids were more affected by the presence of salt and pH changes, with a greater decline in viscosity and increase in filtrate volume. This behaviour was interpreted as conformation adopted by the kappa-carrageenan chains in the presence of ions, indicating that this polymer is a good candidate for drilling fluids in oil well operations.