Preparation and Solution Properties of Zwitterionic Polyacrylamide for Enhancing Oil Recovery

The viscosity stability of the polymer solution is one of the challenges in enhancing oil recovery and zwitterionic copolymer presents excellent viscosity stability and emulsification performance, enabling effective control the oil/water interface mobility and enhancing oil recovery. Herein, a zwitterionic copolymer (P(AM/AMBS/MAPTAC)) containing sulfonic acid group and quaternary amine group was synthesized by segmentation initiation with AM, AMBS and MAPTAC as monomers. The chemical structure of P(AM/AMBS/MAPTAC) was confirmed by FTIR and ¹H NMR. The M_w value of (P(AM/AMBS/MAPTAC)) was 9.91×10⁶, and the apparent viscosity of the solution of 2000 mg/L solution was 24.92 mP·s at 60 ℃ in the 5000 mg/L salt solution. P(AM/AMBS/MAPTAC) with the sulfonic acid group and the quaternary amine group exhibits outstanding salt tolerance and shear resistance. When the salinity was 10000 mg/L and the shear rate was 300 s^-1, the apparent viscosity and the viscosity reduction rates for the P(AM/AMBS/MAPTAC) solution were 23.45 mP·s and 69.23 %, respectively. Moreover, P(AM/AMBS/MAPTAC) exhibited higher emulsion property and higher oil-water interface thickness than HPAM and SPAM because of the synergistic effect of sulfonic acid and quaternary amine groups in the P(AM/AMBS/MAPTAC) molecule. The polymer flooding and the alkali-surfactant-polymer flooding formed by P(AM/AMBS/MAPTAC) had high chemical oil recovery and the oil displacement efficiency was higher than HPAM and SPAM in the polymer flooding and the alkali-surfactant-polymer flooding systems.