Self-Assembly Systems\nBased on Betaine-Type Hydrophobic\nAssociation Polymer Used in Acid Stimulation: Effects of Surfactant\nand Salt Ion

Hydrophobic association polymers containing various functional\ngroups have a great deal of application potential as a self-thickening\nagent in carbonate acidification, while the improvement of their viscosification\nability under high temperature conditions remains a significant challenge.\nA kind of betaine-type hydrophobic association polymer (PASD) intended\nfor use as an acid thickener was synthesized through aqueous solution\npolymerization with sulfobetaine and a soluble hydrophobic monomer.\nThe structure of PASD was characterized by FT-IR and <sup>1</sup>H\nNMR. It is found that during the acid-rock reaction, the physical\ncross-linking between PASD and cationic surfactants (STAC) occurs\nthrough noncovalent bonding forces such as micellar interaction and\nelectrostatic interaction, forming a self-assembly acid. The optimum\nconditions for the construction of the self-assembly acid and its\nviscosification properties, rheological properties, temperature, and\nsalt resistance were evaluated by a six-speed rotating viscometer\nand a HAAK MARSIII rheometer. The results suggest that the main source\nof the viscosity rise of the self-assembly acid is the CaCl<sub>2</sub> produced during the acid-rock reaction. As the acid-rock reaction\nprogresses, the hydrodynamic radius of the self-assembly acid increases,\nand tighter aggregation structures form. The viscosity of the self-assembly\nspent acid still keeps in 140 mPa·s under 140 °C shearing\nfor 1 h at 170 s<sup>–1</sup>, which indicates that the self-assembly\nacid has excellent viscosification ability and temperature resistance.\nCompared to PASD acid, the self-assembly acid can be used at a wider\nrange of temperatures, and its research and development have given\nrise to novel ideas for the use of HAWPs as an acid thickener.