| As an important non-renewable resource,oil plays a crucial role in national progress and economic development.Based on the current situation of oil resource exploitation in our country,it can be seen that after primary and secondary oil recovery,a large amount of crude oil remains in reservoirs with relatively harsh environments.In order to further improve oil recovery,tertiary oil recovery technology has been gradually improved,and polymer flooding in chemical testing has been widely used due to its strong practicality and applicability.In traditional polymer flooding processes,polymer polyacrylamide with linear molecular structure is widely used to improve oil recovery due to its low cost and ease of preparation.To a certain extent,polyacrylamide can be used to increase the viscosity of displacement fluids and improve the mobility ratio between the oil phase and the displacement agent phase,in order to improve oil recovery.However,polyacrylamide is prone to hydrolysis and precipitation in harsh reservoir environments,which makes the performance of polyacrylamide in enhancing oil recovery not ideal.In order to improve the above situation,this study starts with changing the structure of the polymer,using hydroxypropyl methyl cellulose(HPMC)as the main chain of the polymer,acrylamide(AM),and methylallyl polyoxyethylene ether(HPEG)as functional monomers,a thermo-viscosifying water-soluble graft polymer(PHAH)for enhanced tertiary oil recovery was synthesized using aqueous solution free radical polymerization to avoid the problems of instability and easy decomposition of the polymer during displacement.The structure of the polymer was characterized by Fourier transform infrared spectroscopy(FT-IR),nuclear magnetic resonance(1H NMR),scanning electron microscopy(SEM),and thermos-gravimetric analysis(TGA).The test results showed that AM and HPEG were successfully grafted onto the main chain of HPMC.Then,Ubbelohde viscometer was used to test the molecular weight of the polymer,and the systematic rheological properties of the polymer were tested,such as temperature resistance,viscosity enhancement,salt resistance,shear resistance,shear recovery,viscoelasticity and aging resistance.Through core displacement experiments,the displacement performance of the polymer was characterized.The results show that in deionized water and simulated mineralized water solutions,compared to traditional polymer flooding agent PAM,grafted polymer PHAH solution exhibits excellent temperature increasing viscosity and better temperature resistance and salt resistance.This is due to the coordination between the rigid sixmembered ring structure of the grafted polymer backbone HPMC and the temperature sensitive ether macro-monomer HPEG,resulting in a three-dimensional network spatial structure of the polymer solution.In the anti-aging test,PHAH solution showed good anti-aging performance.In core displacement experiments,PHAH enhanced oil recovery by 23.2%,higher than 14.5%of PAM.These results indicate that PHAH is more suitable for improving oil recovery(EOR)than PAM in this study.Subsequently,by mixing PHAH with cationic surfactant(DTAB),nonionic surfactant(OP-10),and anionic surfactant(SDS).The results showed that the composite system composed of DTAB and polymer generates precipitation,and the compound system is unstable;When OP-10,SDS and polymer are mixed,the apparent viscosity of the mixed system solution shows a phenomenon of first increasing and then decreasing with the increase of the amount of surfactant added,which conforms to the three-stage model proposed by Biggs for the synergistic effect of hydrophobic associating polymers and surfactants.Determine the compound system with the best synergistic effect.Through rheological performance testing,it is found that the rheological properties of the compound system have been further improved compared to a single PHAH solution,and the potential for using it as a displacement fluid to enhance oil recovery is greater. |
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