Failure mechanism analysis for AMPS-family polymers in high-salinity hydrothermal environments

Abstract

Polymers derived from 2-acrylamido-2-methylpropane sulfonic acid (AMPS) are extensively employed as chemical additives in oil and gas drilling operations. However, as drilling increasingly targets deep and ultra-deep reservoirs, AMPS-family polymers also undergo functional degradation as the extreme downhole conditions of high salinity (up to saturation), high pressure (45–150 MPa), and high temperature (150–250 °C). This review is the first to focus on the special topic, i.e., failure mechanism of AMPS-family polymers in high-salinity hydrothermal environments. More than ten chemical groups have been identified from 36 monomers that are commonly used for synthesizing AMPS-family polymers. Their polymer functions, degradation mechanisms and improvement methods are discussed in details combining with the physicochemical properties of high-salinity subcritical water. Acid-catalyzed hydrolysis is identified as the predominant degradation mechanism. The hydrothermal stability of functional groups follows the order: benzene > organosilicon > quaternary ammonium > sulfonic acid > heterocycle > amide > carboxylic acid > ether > alcohol > ester. Key strategies for enhancing stability include controlling drilling mud pH and increasing polymer steric hindrance. Future fundamental research is recommended to focus on inorganic salt behavior in complex subcritical water systems, hydrothermal reaction pathways of relevant monomers and polymers, and the development of next-generation polymers incorporating novel functional groups. Information provided by this review can promote a better understanding of polymer behaviors in high-salinity hydrothermal environments, a guideline for selecting suitable monomers, and recommendations for new polymer development.