A Study on the Thermal Degradation of an Acrylamide and 2-Acrylamido-2-Methylpropanesulfonic Acid Copolymer at High Temperatures

Abstract

As a temperature-resistant and salt-resistant polymer, acrylamide and 2-acrylamide-2-methylpropane sulfonic acid (abbreviated as AM-AMPS) copolymer is currently widely used in drilling, water control and oil production stabilization, enhanced oil recovery and other fields, but its stability under high temperature has been less studied. The degradation process of the AM-AMPS copolymer solution was studied by measuring viscosity, the degree of hydrolysis, and weight-average molecular weight at different temperatures and aging time. During the high-temperature aging process, the viscosity of the AM-AMPS copolymer saline solution first increases and then decreases. The combined action of the hydrolysis reaction and the oxidative thermal degradation leads to the change of the viscosity of the AM-AMPS copolymer saline solution. The hydrolysis reaction of the AM-AMPS copolymer mainly affects the structural viscosity of its saline solution through intramolecular and intermolecular electrostatic interactions, while the oxidative thermal degradation mainly reduces its molecular weight by breaking the main chain of the copolymer molecules, reducing the viscosity of the AM-AMPS copolymer saline solution. The content of AM and AMPS groups in the AM-AMPS copolymer solution at various temperatures and aging time was analyzed using liquid nuclear magnetic resonance carbon spectroscopy, demonstrating that the hydrolysis reaction rate constant of AM groups was significantly higher than that of AMPS groups. The contribution values of hydrolysis reaction and oxidative thermal degradation of the AM-AMPS copolymer at different aging time to viscosity were quantitatively calculated at temperatures ranging from 104.5 °C to 140 °C. It was determined that the higher the heat treatment temperature, the smaller the contribution of hydrolysis reaction to viscosity, while the bigger the contribution of oxidative thermal degradation to the viscosity of the AM-AMPS copolymer solution.

Synthesis and performance evaluation of a novel zwitterionic quaternary copolymer for enhanced oil‐recovery application

“…It can be found that the apparent viscosity of AA/AM/AOS/C 16 ‐DMAAC increased firstly with the increasing concentration of NaCl, reaching the maximum (about 350 mPa·s) at 2000 mg/L of NaCl, then gradually decreased with the increment of mineralization degree. Specifically, at low salinity degree, the hydrophobic association of AA/AM/AOS/C 16 ‐DMAAC was enhanced by the influence of salt ions, improving the apparent viscosity of AA/AM/AOS/C 16 ‐DMAAC 27,29,30 . While the anti‐polyelectrolyte effect of AA/AM/AOS/C 16 ‐DMAAC was significant after concentration of NaCl exceeding 2000 mg/L.…”

“…Especially, from 30 °C to 70 °C, apparent viscosity of AA/AM/AOS/C 16 ‐DMAAC decreased from 364 to 294 mPa·s, while the apparent viscosity of HPAM decreased from 188 to 104 mPa·s. In addition, the temperature‐resistance of AA/AM/AOS/C 16 ‐DMAAC (with a viscosity retention rate of 77.94%) was better than that of HPAM (with a viscosity retention rate of 55.26%) at 70 °C, which can be attributed to introduction of sulfonic acid groups into AA/AM/AOS/C 16 ‐DMAAC for inhibiting it hydrolysis at high temperatures 26,27 …”

“…Klucker et al 25 found that hydrophobic association polymers will form a network structure in aqueous solution, leading to the improvement of salt resistance. Based on the fact that sulfonic acid groups can improve temperature‐ and salt‐resistance of polymers, 26,27 and hydrophobic groups (C 16 ‐DMAAC) can improve the viscosity and the shearing resistance of polymers 28–30 . However, hydrophobic monomers and sulfonate group‐containing monomers were not used simultaneously in the above studies, which resulted in limited improved performance of those reported polymers.…”