| In tertiary oil recovery,modified HPAM with different structures has made great progress in oil displacement,using functional groups with different properties introduced into the molecular backbone to enhance its ability to resist harsh oil and gas reservoirs,such as the introduction of zwitterionic groups to enhance its salt resistance,the introduction of rigid groups to increase its temperature and shear resistance,and the introduction of hydrophobic groups to create a hydrophobic association effect to enhance its viscosity and viscoelasticity.In this paper,water-soluble chitosan monomer was synthesized by maleylation of chitosan.Five chitosan-functionalized acrylamide polymers were synthesized using chitosan monomer as functional monomer and acrylamide,acrylic acid,twin-tailed monomer,zwitterionic monomer,imidazoline monomer and ?-cyclodextrin monomer.The basic properties of the polymers were studied and it is expected to be excellent in enhancing oil recovery.The main research contents are as follows:1?Water-soluble chitosan monomer(CTAH)was synthesized from maleic anhydride and chitosan.Twin-tailed monomer(DLMB)was synthesized from di-n-octylamine and methacryloyl chloride.Zwitterionic monomer(MDPS)was synthesized from N-(3-dimethylaminopropyl)methacrylamide and 1,3-propylsulfonolactone.Imidazoline monomer(NIDA)was synthesized from 1-(2-aminoethyl)-2-oleic acid imidazoline and acryloyl chloride.?-cyclodextrin monomer(O-?-CD)was synthesized from ?-cyclodextrin,p-toluene sulfonyl chloride,ethylenediamine and acryloyl chloride.The five monomers were characterized by FT-IR and 1H NMR,and their structures were consistent with the target monomers.2?Five chitosan-functionalized water-soluble hydrophobic associative polymers(AAC,AACD,AACM,AACN and AACO)were prepared by free radical copolymerization with CTAH,DLMB,MDPS,NIDA,O-?-CD,acrylamide(AM)and acrylic acid(AA)under oxidation-reduction initiator system.The optimal synthesis conditions,molecular structure,intrinsic viscosity and thermal stability of the five polymers were investigated.3?Through the study on the viscosifying,viscoelasticity,shear resistance,shear recovery,aging resistance and temperature and salt resistance of chitosan-functionalized polymers,it is concluded that chitosan-functionalized polymers have excellent viscosifying properties.When the concentration of polymer solution is 2000 mg/L,their viscosities are AAC:424.7 mPa s,AACD:568.4 mPa s,AACM:515.8 mPa s,AACN:486.5 mPa s and AACO:532.2,respectively.Under the fixed stress of 1 Pa,the storage modulus and loss modulus of chitosan-functionalized polymer solution are better than those of HPAM,indicating that it has excellent viscoelasticity.When the shear rate ?=510 s-1,the viscosity retention of the chitosan-functionalized polymer solution is higher than that of HPAM,showing better shear resistance.In the range of shear rate of ?=170?510?170 s-1,the chitosan-functionalized polymer solution can recover to its initial value well,while the viscosity of HPAM is significantly reduced.After 30 days of aging experiment,the viscosity of chitosan-functionalized polymer solution is AAC:69.4 mPa s,AACD:104.2 mPa s,AACM:96.5 mPa s,AACN:117.5 mPa s and AACO:124.3 mPa s,and the retention values are much higher than that of HPAM(12.4 mPa s).When the temperature is 120?,the viscosity retention values of chitosan-functionalized polymer solution are higher than that of HPAM,which have good temperature resistance.Under the conditions of Na+=15000 mg/L,Mg2+=2000 mg/L and Ca2+=2000 mg/L,the viscosity retention values of chitosan-functionalized polymer solution are still higher than HPAM,indicating that they have better salt resistance.performance.4?The simulated core flooding experiment was carried out at 70?,and it was found that the chitosan-functionalized polymers have higher oil recovery capacity.Compared with water flooding,all tetrabasic chitosan-functionalized polymers can increase EOR by at least 8%,and the polymer AACO with the highest oil displacement efficiency increases the EOR by 9.35%. |
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