Zhao Fangyuan

Synthesis and performance evaluation of temperature-tolerated and salt-resisted polymers for tertiary oil recovery

The copolymer (AM-AANa-AMPSNa) was synthesized by solution polymerization of acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and sodium hydroxide (NaOH) with (NH 4 ) 2 S 2 O 8 , Na 2 SO 3 and N(CH 3 ) 2 CON(CH 3 ) 2 as initiator. The effects of initiator content, monomer concentration, pH and reaction temperature on the viscosity-average molecular weight were investigated, and the optimal conditions were obtained: the initiator content of 0.035%, the monomer concentration of 25%, pH 7, reaction temperature of 0 ℃. The structure of copolymer was characterized by IR spectrum and 13 C NMR spectroscopy. In the performance experiments, physicochemical properties, viscoelasticity, injection, oil displacement were evaluated. Results indicated that the copolymer (AM-AANa- AMPSNa) demonstrated superior temperature-resistance and salt-resistance compared to higher molecular weight partially hydrolyzed polyacrylamide (HPAM). It was found that the viscosity-average molecular weight of the copolymer could reach 3.0 × 10 7 , and the viscosity of the copolymer solution, obtained with Shengli III salt water could reach 17.7 mPa s at the concentration of 1500 mg/L at 85 ℃. The simulative oil displacement signified that copolymers (AM-AANa-AMPSNa) could remarkably enhance 15.8% of oil recovery ratio, especially after water flooding at the oil recovery ratio of 51.8%. These features indicated that the copolymers had a great potential application for tertiary oil recovery, especially in high-temperature and high-mineralization oil fields.