Associating Copolymer Acrylamide/Diallyldimethylammonium Chloride/Butyl Acrylate/2-Acrylamido-2-methylpropanesulfonic Acid as a Tackifier in Clay-Free and Water-Based Drilling Fluids

Drilling fluids must possess optimal rheological properties, such as shear thinning and thixotropy, and the key materials to control these properties for clay-free and water-based drilling fluids (CFWBDFs) are organic polymers. To overcome the challenge, associating copolymer P(AM/DMDAAC/BA/AMPS) (ADBA) of acrylamide (AM), cationic monomer diallyldirnethylammonium chloride (DMDAAC), hydrophobic monomer butyl acrylate (BA), and anionic monomer 2-acrylamido-2-methylpropanesulfonic acid (AMPS) was synthesized. As a result of the intra-/intermolecular associations, a network structure was observed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. With increasing concentrations, the apparent viscosity (AV), viscoelasticity, and thixotropy of the aqueous solution were enhanced. The AV of the aqueous solution containing 0.6 wt % ADBA was 46 mPa s, more than double that of common tackifier potassium polyacrylamide (K-PAM). ADBA appeared as an excellent tackifier and possessed better rheological properties than K-PAM. The laboratory test showed that ADBA effectively controlled the rheology and filtration loss of drilling fluids. Meanwhile, CFWBDFs with ADBA possessed better shear thinning than CFWBDFs with K-PAM. Therefore, the new copolymer had good potential for application in CFWBDFs.