Rheological and filtration properties of clay-polymer systems: Impact of polymer structure

In this study, the effect of polymer structure, the degree of hydrolysis, chemical structure of monomer in the backbone, and charge distribution of monomer groups on rheological and filtration properties of Bentonite (Bent)/polymer dispersions were assessed. Two different water-soluble polymers were employed to investigate the rheological and filtration properties of Bent/polymer dispersions. The polymers evaluated are a copolymer of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid (AM-AMPS) (P1) and a terpolymer of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, and N-Vinylpyrrolidone (AM-AMPS-NVP) (P2). The objective of this work was to study the rheological and filtration properties of Bent/polymer dispersions in deionized and salt water at different temperatures (25 °C and 85 °C). The steady shear rheological data was fitted to Herschel-Bulkley model to compute rheological parameters like yield stress, consistency index, and flow behavior index. The incorporation of polymers in Bent dispersions improved the rheological properties of the Bent dispersions. Addition of electrolyte in Bent/polymer dispersions led to a slight decrease in the rheological properties of all developed dispersions. The Bent/P2 dispersion revealed superior rheological properties compared to the other Bent and Bent/polymer dispersions in both deionized and salt water. TEM analysis of Bent/polymer dispersions was carried out to study the morphology of dispersions. LP/LT and HP/HT filtration experiments were performed in deionized and salt water at 25 °C and 85 °C, respectively, and results showed that Bent/P2 dispersion had minimum filtrate volume and filter cake thickness compared to the Bent dispersion. The permeability of filter cakes was determined using Darcy's law and filter cake morphologies were studied using SEM analysis. The excellent rheological and filtration properties of Bent/P2 dispersion was attributed to the presence of NVP monomer group in P2 polymer, which is stable towards elevated temperatures and high salinity environments. The exceptional filtration and rheological properties of P2 polymer make it a suitable candidate for the development of high-performance drilling fluids.