Study On The Synthesis And Properties Of Betaine-type Hydrophobically Associating Polymers

Tertiary oil recovery technology is the further innovation which is based on the secondary water flooding technology through the physical and chemical methods.Polyacrylamide(PAM)and partially hydrolyzed polyacrylamide(HPAM)are the main polymer flooding and widely used in oilfield due to the low cost,widespread source and the advantage of good thickening ability.But the PAM and HPAM are easy to lose the displacement performance because of degradation when the reservoir conditions become harsh enough,such as high temperature,high pressure,and high salinity with the further exploitation which can't meet the needs of the practical projects.In recent years,it's found that the displacement performance of polymer can be improved and enhanced effectively owing to the different groups are introduced into the main chain of PAM and HPAM,such as anti-polyelectrolyte effect of zwitterionic groups with salt resistance,rigidity of the benzene ring with better shear resistance and temperature resistance,hydrophobic association effect from hydrophobic groups with improvement of viscosifying ability and viscoelasticity,thus can significantly improve performance of polymer displacement.In this paper,three sets of different polymers are prepared by free radical copolymerization in aqueous solution through a peroxidation-reduction system with acrylamide(AM),acrylic acid(AA),hydrophobic monomers and zwitterionic functional monomer,the main research contents are as follows:(1)The hydrophobic monomer N-allyl-2-phenoxyacetamide(NAPA)was prepared by phenoxyacetic acid,thionyl chloride and allylamine(AP).The benzenesulfonamide hydrophobic monomers N-allyl-4-methylbenzenesulfonamide(TCAP)and N,N-diallyl-4-methytbenzenesulfonamide(TCDAP)were prepared by 4-toluene sulfonyl chloride(MBSC),allylamine(AP)and diallylamine(DAP),respectively.The zwitterionic functional monomer 3-(3-methylacrylamidopropyldimethylamino)-propane-1-sulfonate(MDPS)was prepared by N-(3-dimethylaminopropyl)-methacrylamide(DMAPMA)and 1,3-propanesultone.All the monomers were proved by FT-IR and 1H-NMR.(2)Three sets of betaine hydrophobic associating polymers P(AM/AA/NAPA/MDPS),P(AM/AA/TCAP/MDPS)and P(AM/AA/TCDAP/MDPS)were prepared by free radical copolymerization in aqueous solution with ammonium persulfate and sodium bisulfite as initiator system.Structural characterization were conducted by FT-IR and 1H-NMR,the molecular weight were conducted by intrinsic viscosity,and the thermal stability was evaluated by TG-DTG.The optimum synthesis conditions of three copolymers were obtained by single factor methods:P(AM/AA/NAPA/MDPS):m(AM):m(AA):m(NAPA):m(MDPS)=7:3:0.05:0.20,pH=7,reaction temperature(50?),initiator dosage(0.5wt%),reaction time(6 h);P(AM/AA/TCAP/MDPS):m(AM):m(AA):m(TCAP):m(MDPS)=7:3:0.10:0.05,p H=7,reaction temperature(45?),initiator dosage(0.5wt%),reaction time(5 h);P(AM/AA/TCDAP/MDPS):m(AM):m(AA):m(TCDAP):m(MDPS)=6:4:0.01:0.10,pH=7,reaction temperature(50?),initiator dosage(0.6wt%),reaction time(8 h).The intrinsic viscosities of the three sets of polymers under the optimal synthesis conditions were 890.14 mL/g,663.49 mL/g and 893.05 mL/g respectively.(3)The thickening ability,temperature resistance,ageing stability test,anti-shearing,viscoelasticity and salt tolerance of the betaine hydrophobic associating polymers were investigated simultaneously,the thickening ability of P(AM/AA/TCDAP/MDPS)was better than P(AM/AA/NAPA/MDPS)and P(AM/AA/TCAP/MDPS);the anti-shearing ability of the three sets of polymer solutions was all better than that of HPAM under the shear rates of 500 s-1 at 25?;When the temperature rose to 120?,the temperature resistance of the three sets of polymer solutions was also better than that of HPAM;When the stress was stabilised at 1 Pa,the energy storage modulus and energy dissipation modulus of the polymer solution were both higher than HPAM;In 10000mg/L NaCl,2000mg/L CaC12 and 2000mg/L MgCl2,the apparent viscosity of the three sets of polymer solutions were also higher than HPAM.(4)Micromorphology of polymers by SEM revealed that polymers showed a multi-layer three-dimensional dense network structure compared with HPAM.Specifically,the tightness between the molecular chains is great and many small holes covered by the wound molecular chains was inlaid in network structure.Entanglement of the molecular chain is deep in an orderly great connective.Moreover,AM/AA/TCDAP/MDPS behaved the closest structure network,the number of the most stereoscopic structures and the smallest inlaid holes in the network structure in contrast with the most loose network structure from HPAM.(5)Flow control ability and EOR were evaluated by simulated core flooding experiment at 65?.Compared with HPAM,three sets of polymers solutions all showed stronger flow control ability and higher oil recovery rate.