Synthesis and molecular dynamics simulation of amphoteric hydrophobically associating polymer

Abstract

To address the practical issues of poor temperature and salt tolerance of polymers, a new amphoteric monomer (E)-N-(docos-13-enoyl)-N-methylglycine named CQ was developed. The polymer CQMP was synthesized by acrylamide (AM) and CQ as an associative monomer and sodium p-styrene sulfonate (SSS) as a functional monomer in aqueous solution. The structure of the products was confirmed by FTIR, 1H NMR and TGA, while the micro-morphology of the polymer was observed by SEM. Taking HAPAM as a control, the properties of polymer in aqueous solution were studied as a function of salinity, shear rate, temperature, and polymer concentration. The oil displacement performance was also evaluated in detail. Additionally, the surface tension (SFT) and interfacial tension (IFT) of CQMP solution were measured. The critical micelle concentration (CMC) values of CQMP in aqueous solution and in NaCl solution are 2.13 g·L-1 and 1.79 g·L-1,respectively. The copolymer can reduce the interfacial tension between water and crude oil from Changqing Oilfield, with an IFT value of about 15.96 mN·m−1. The results indicate that the critical association concentration (CAC) is approximately 600 mg·L-1, and the polymer exhibits good salt tolerance and oil flooding performance. Furthermore, molecular dynamics simulation demonstrated that CQ can enhance intermolecular interactions while maintaining the same hydrophobic chain content, thereby reinforcing the polymer’s resistance temperature and salt. The laboratory flooding experiment showed that the enhance oil recovery of CQMP with 0.5 PV 3000 mg·L-1 was 12.23 % greater than that of HAPAM, which is promising for multiple applications in complex oil fields.