| Polymer flooding is one of the most widely and effective technologies at the technology of EOR.With the development of crude oil,Geological conditions are extremely complicated,and the polymer of flooding is also required to have some properties.In order to adapt the conditions of complex reservoir,the polymer of flooding gradually develop from linear polymer to branched polymer and then to hyperbranched polymer.Based on the previous works of our research group,a modified nano-SiO2/AA/AM copolymer was sythesised for improving anti-shear performance and sweep efficiency,and its improving sweep efficiency was studied by lab flooding test.This paper further studies the characterization methods of the different degree of modified nano-SiO2,and studies the molecular structure and solution structure of and hyperbranched polymers based on the different degree of modified nano-SiO2,these researches will be helpful to understand the hyperbranched polymer,nano-SiO2 as a core.In order to accurately characterize and determine the degree of modification.the modified nano-SiO2(NSI)was synthesized by using 3-aminopropyltrimethoxysilane(KH540)under the optimized experimental conditions.The amount of hydroxyl group on the nano-SiO2 surface was 2.1201 mmol/g,based on the amount of hydroxyl geoup,the content of KH540 of the different modification degree of nano-SiO2 were evaluated.NSI-20,NSI-40,NSI-60,NSI-80 and NSI-100 were prepared,a series of qualitatively characterize experiments,such as IR,1H-NMR,and ESEM.were performed,and a series of quantitatively characterize experiments,such as EA.TGA,and DLS,were also performed.The content of amino groups from NSI-20,NSI-40.NSI-60,NSI-80 and NSI-100 were 0.1571,0.2928,0.4143,0.5786,0.7143 mmol/g,respectively by electrical conductibility method.The content of amino groups from NSI-20,NSI-40,NSI-60,NSI-80 and NSI-100 were 0.1489,0.2752,0.4121,0.5593,0.7166 mmol/g,respectively by spectrophotometry.This paper introduces a new methodology to control the degree of modification of nano-SiO2,and the characteristic tests prove that modified nano-SiO2 can not only be qualitatively studied.but also be quantitatively analyzed.The modified nano-SiO2 hyperbranched polymer(HBPS),consisting of polyacrylamide as hydrophilic branched chains and modified nano-SiO2 as the core,was synthesized via an in-situ free radical polymerization reaction under the optimized experimental conditions.The molecular structure of HBPS were studied by qualitatively and quantitatively methods.The absolute weight-average molecular weight of the hyperbranched polymer with different degree of modification of nano-SiO2 was determined by static light scattering,and it shows the rule of increase firstly and then decrease with the growing of the degree of modification,the absolute weight-average molecular weight of HBPS-20,HBPS-40,HBPS-60,HBPS-80,HBPS-100 were 4.43×106,5.72×106,6.78×106,3.72×106,2.19×106 g/mol,respectively.The hydrodynamic radius was measured by dynamic light scattering,and it shown the rule of decreasing with the growing of the degree of modification,the hydrodynamic radius of HBPS-20,HBPS-40,HBPS-60,HBPS-80,HBPS-100 were 216.20,186.62?176.12,168.96,160.55 nm,respectively.The experiment result of TGA shown the higher the retention rate with the growing of the degree of modification.The study of molecular structure shown that the modified nano-SiO2 hyperbranched polymers is more and shorter branched chains with the increase of modification degree of nano-SiO2.The molecular structure and the relationship of molecular and solution structure of the hyperbranched polymer solution were studied,and the results shown that the tackify character,salt resistance,temperature resistance all increased firstly and then decreased,but shearing resistance increased gradually with the growing of the degree of modification.The dynamic viscoelasticity of the hyperbranched polymer solution with different degree of modification of nano-SiO2 were measured.It was concluded that the elasticity increased gradually but viscosity decreased generally with the growing of the degree of modification.The microstructure of the hyperbranched polymer with different degree of modification of nano-SiO2 was observed by using scanning electron microscope under different magnification conditions.It was found that the larger the degree of modification,the smaller the hydrodynamic radius and the denser the network structure of the microstructure.The result of solubility experiment shown a gradually decrease with the growing of the degree of modification.The result of hydrolysis degree experiment shown a generally increase with the growing of the degree of modification.The results of the relationship of molecular and solution structure shown the different solution structure was decided to the different molecular structure. |
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