Performance and Characteristics of Low-Molecular-Weight Cross-Linked Grafting Terpolymers as Thickening Agents in Reservoir Fracturing Processes

A novel fracture fluid based on a grafting polymer, PAM-co-PAMS-g-PEG (PAM-AMS-AEG), cross-linked by an organic Zr reagent was successfully produced via free-radical polymerization and an in situ cross-linking reaction with a high conversion rate of 96%, resulting in a low molecular weight of 250 kg·mol−1. The effect of fluid constitution on the rheological behavior demonstrates that the P(AM10-AMS2-AEG1.4)/[Zr]0.35/TBAC0.1 (PASG/[Zr]) aqueous solution has the best comprehensive performance. The PASG/[Zr] solution with a low critical associating concentration (CAC) of 0.15 wt% showed faster and steadier disassociation–reassociation processes. The synergy of ionic hydrogen bonds between sulfonic and amine groups and Zr4+-coordination results in steady interactions and fast reconstitution of association, leading to remarkable temperature resistance from 30 to 120 °C and a fast response during thixotropic processes. The PASG/[Zr] solution reduces the damage under high pressure based on the rheological characteristics and compatibility with sand, leading to a low filtration loss of the artificial cores. The PASG/[Zr] solution exhibits a good sand-carrying ability based on the rheological and interfacial performance, resulting in slow settlement and fast suspension. The filtration performance of the PASG/[Zr] fracturing fluid showed that it is not sensitive to the shearing rate, core permeability, or pressure. The comprehensive performance of the PASG/[Zr] fracture fluid is better than that of traditional guar fluid, suggesting that it can be used under various conditions for stratum protection and shale gas extraction.