Synthesis And Properties Of Comb-shaped And Star-shaped Sulfite Salt Zwitterionic Polymers

Acrylamide copolymer with diverse structure has achieved many success in oilfield exploitation compared with hydrolyzed polyacrylamide.The properties of different groups from the comonomers in the backbone,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,obviously amelioratethe rheological properties of HPAM in harsh oil and gas reservoirs and make a great progress in enhanced oil recovery.In this article,maleic chitosan and triethylenetetramine are proposed as the initiating points to build the comb-shaped and star-shaped structure.Further more,zwitterionic monomer containing sulfite inner saltand hydrophobic monomers containing ester and benzene ring are introduced into the backbone of HPAM to strengthen the rheology.The main research contents are as follows:1.Maleic chitosan(N-CTS)or maleated triethylenetetramine(N-TETA)was synthesized with with maleic anhydride,chitosan or ethylenetetramine,respectively.2-((3-methacryIamidopropyl)dimethylammonio)ethyl sulfite(MAPES)was synthesized with vinyl sulfate and N-(3-dimethylaminopropyl)methacrylamide.N,N-diallylamine-p-toluenesulfonamide(DMBSA)was synthesized with p-totuenesulfonyl chloride and diallylamine.All the monomers were proved by FT-IR,1HNMR and/or 13C NMR.2.The synthesis of comb and star-shaped copolymer(N-CTS/MAPES/AM/AA/t-BA,N-CTS/MAPES/AM/AA/DMBSA,N-TETA/MAPES/AM/AA/t-BA and N-TETA/MAPES/AM/AA/DMBSA)was conducted thtough functional monomers including N-CTS,N-TETA,MAPES,DMBSA and tert-butyl acrylate,main chain monomers containing AM and AA.The study of optimum polymerization conditions was carried out through the viscosity of copolymer solution that;initiator(0.03 g),temperature(40?),pH=7,and t-BA(0.2 g),DMBSA(0.03 g),comb-shaped copolymer:N-CTS(0.3 g),MAPES(0.1 g),m(AM):m(AA)=6:4,star-shaped copolymer:N-NENT(0.2 g),MAPES(0.2 g),m(AM):m(AA)=7:3.Structural characterization and molecular weight were conducted by IR?1H NMR and intrinsic viscosity,and thermal stability was evaluated by TG-DTG.3.The study on effect of polymer concentration,shear rate,temperature,metal salt ion(Na+?Mg2+and Ca2+)concentration on the viscosity and effect of scanning frequency on the modulus G"/G' indictated that;(1)critical association concentration was 686,745,815 and 878 mg/L,(2)when ?=300 s-1,the viscosities of copolymer solution were more than HPAM revealing their better shear resistance,(3)the more remarkable shear recovery was confirmed by the recovery rate of 98%>83%of HPAM with ? from 170 to 510 to 170 s-1,(4)when T=100?,? from copolymer was seriously more than HPAM,which suggested the superior temperature tolerance,(5)the copolymer solution also kept high ? in the high salt concentration(Na+=30000 mg/L,Mg2+and Ca2+=3000 mg/L),(6)the remarkable viscoelastic zone from copolymer illustrated their good viscoelasticity.Intrast with synthetic polymer and HPAM,the performance of N-CTS/MAPES/AM/AA/t-BA was the most superior one.4.The study about effect of polymer concentration on the surface tension displayed that the increasing concentration made the surface tension gradually decreased and surface tension stabilized at 57-65 mN/m.N-TETA/MAPES/AM/AA/t-BA showed the highest surface activity with lowest surface tension.And there were different critical micelle concentrations;N-TETA/MAPES/AM/AA/t-BA:808 mg/L,N-TETA/MAPES/AM/AA/DMBSA:821 mg/L,N-CTS/MAPES/AM/AA/t-BA:961 mg/L,N-CTS/MAPES/AM/AA/DMBSA:1006 mg/L.5.Micromorphology of polymers by SEM revealed that polymers showed a multi-layer three-dimensional dense network structure.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,N-CTS/MAPES/AM/AA/t-BA 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 N-TETA/MAPES/AM/AA/DMBSA.6.Flow control ability and EOR were evaluated by simulated core flooding experiment at 75?.The results presented that performance of comb and star-shaped copolymer was all better than HPAM(Rf=8.45,RRf=1.91,EOR:7.21)and copolymer N-CTS/MAPES/AM/AA/t-BA reflected the best flow control(Rf=18.23,RRf=6.62)and bigger value of EOR(13.32%).