Synthesis and performance evaluation of three anti-hydrolysis polymers and its field application

Conventional oil displacement polymers are partially hydrolyzed polyacrylamide （HPAM）. When the temperature is above 80 °C， the hydrolysis rate of acid amide accelerates， and the carboxylic acid produced after hydrolysis is prone to complex with calcium and magnesium ions to form precipitation， which significantly reduces the performance of HPAM. To improve the temperature and salt resistance of the polymer， The polymerization of acrylamide （AM） monomer with three anti-hydrolytic monomers N-vinylpyrrolidone （NVP）， dimethylacrylamide （DMAA）， and 2-acrylamide-2-methylpropanesulfonic acid （AMPS） is often carried out in binary， ternary or quaternary copolymerization， but the influence of each monomer on the properties of polymers has not been deeply studied. So， three kinds of hydrolysis resistant binary copolymers P（AM-AMPS）， P（AM-DMAA）， and P（AM-NVP） were synthesized by copolymerization of three kinds of monomers with AM respectively. The effects of the introduction of three monomers on polymer properties were investigated. The results show that the introduction of 20% NVP， DMAA， and AMPS on the HPAM main chain leads the viscosity-average molecular weight of the polymer to reduce from 3 050×104 to 720×104， 1 500×104 and 2 800×104， respectively. The average hydrodynamics diameters decrease by 39.5%， 27.7%， and increase by 12.4%， respectively. The effect of the introduction of AMPS on the molecular weight of HPAM was significantly smaller than that of NVP and DMAA. Due to the lack of complexation between the sulfonic acid anion in AMPS and calcium and magnesium ions， the strong intermolecular repulsion allows molecular chains to be more stretched in aqueous solutions， which significantly improves the viscosity， viscoelasticity， and thermal stability of the polymer. The results of laboratory and field experiments show that P（AM-AMPS） can significantly improve the oil displacement performance of the polymer under high temperature and high salt reservoir conditions， indicating a broad application prospect.