Use of statistical design to study the influence of CMC on the rheological properties of bentonite dispersions for water-based drilling fluids

The influence of carboxymethyl cellulose, CMC, on the apparent and plastic viscosities of bentonite dispersions for water-based drilling fluids was investigated based on the statistical design. Ten formulations using bentonites, and high and low molar mass CMCs were used in the experiment design. Dispersions were prepared according to Petrobras company standards. Regression models were calculated, correlating the properties with the compositions. The significance and validity of the models were confirmed by statistical analysis and verification experiments. The regression models were used to analyze the influence of CMC content on the properties of bentonite-water dispersions. The statistical design can be applied to optimize mud properties considering CMC addition, and to gain a better understanding of the influence of polymer additives on the properties of bentonite-water systems. (C) 2010 Elsevier B.V. All rights reserved.