Synthesis And Properties Of A Heat-resistant And Salt-tolerant Hydrophobic Associating AM/AMPS/OA Terpolymer

Now many oilfields have entered the high water cut stage of tertiary oil recovery.The studies of indoor researches and field tests on the polymer flooding technology show that polymer flooding is an effective way to enhance oil recovery, and has a broad application prospect. The extensive used partially hydrolyzed polyacrylamide(HPAM) has certain oil displacement effect. However, the apparent viscosity of HPAM solution declines precipitously with the increase of salinity. Meanwhile, the high temperature under deep oil well reservoir impacts the thermal stability performance of HPAM. In addition, in the process of injection of polymer solution,the bottom hole will cause strong shear to the polymer, which will rupture the molecule chain of HPAM, leading the great reduction of apparent viscosity. Therefore, the oil displacement of HPAM is not ideal with high salinity, temperature and shear. How to improve the heat-tolerance and salt-resistance, has become the urgent need to solve this technical problem.In order to solve this problem, a modified polyacrylamide was synthesized by acrylamide(AM), 2-acrylamide-2-methyl propane sulfonic acid(AMPS) and n-octyl acrylate(OA) using micellar polymerization technology from the aspect of molecular structure. Systematically studied the influence of initiator mass fraction, reaction temperature, initiator, the molar ratio of oxidant and reducing agent, the mole ratio of AM and AMPS, SDS content and hydrophobic monomer content on the intrinsic viscosity and the apparent viscosity of polymer solution, and the appropriate reaction conditions were obtained.The structure of hydrophobic associating polymer was characterized by FT-IR, 1H-NMR, indicating that the polymer is a terpolymer of AM, AMPS, and OA. The thermal stability property of the polymer was measured using thermogravimetric analysis(TGA), showing that the initial decomposition temperature is 222℃ and the polymer has good thermal stability.The good solubility and ionization AMPS monomers are introduced to the main chain. And the ionization of sulfonic acid groups in water make the polymer chain extension and prompt hydrophobic association,enhancing the thickening capacity of the polymer solutions. Meanwhile, the AMPS and hydrophobic monomers including in the polymer improve the properties of salt-resistance and hydrolysis resistance. Investigations on the thickening capability, heat-resistance and salt-resistance show that the polymer has adaptability on a wide range of salinity and temperature whose performance is much better than HPAM with a molecular weight of 1600 × 104. The result show that the polymer used in polymer flooding can ideally improve water flooding contradictions,and it is good for the polymer system promoting and applying in different salinity and temperature reservoir.The indoor oil displacement effect of the heat-resistant and salt-tolerant hydrophobic associating polymer was evaluated. On the slug size of 0.25 PV, the hydrophobic associating polymer flooding has enhanced by 12.8% more than that of water displacement, increasing 6.5% compared with HPAM. The result shows that the polymer has great potential in enhanced oil recovery and application.