Size,Morphology And Influence Factors Of Polymer Aggregates In Water

Polymer flooding has a wide range of applications in enhanced oil recovery.The polymers used in polymer flooding mostly are high molecular polymers.It exists in the form of molecular coils in aqueous solutions.The size and morphology of polymer molecular coils will change with the solution concentration,polymer molecular weight,salinity,temperature and other parameters.The change of polymer aggregation morphology will obvious influence on the fluidity of the polymer solution,which will lead to changes the water and oil flow velocity ratio and the conformance efficiency,and then affect the oil recovery.On the other hand,there is a size matching problem between molecular coil formed by polymer in the solution and the pore throat of reservoir.If the matching is poor,oil-displacing effect will also decrease.In order to promote polymer flooding to newly developed low permeability oilfield and ultra-low permeability oilfield.The size and shape of polymer molecular coils in water are systematically studied.To this end,this article conducted a series of studies and some significant results have been obtained:1.Firstly,by improving the existing sample preparation method of transmission electron microscope,a method for detecting the morphology of polymer aggregates in aqueous solution and a sample preparation tool have been developed.The method has the advantages of operation simple,low cost,multiple samples can be prepared at the same time,and detection period is short,etc.With this sample preparation method,the aggregation morphology of the polymer in water can be observed intuitively.2.The aggregation behavior of ultra-high molecular weight polyacrylamide in water was systematically studied by laser light scattering and TEM.It was found that the size of the molecular coils formed by polymers in water decreased with the increase of molecular weight,and the morphologies of polymer molecular coils with different molecular weight were significantly different.Temperature has little effect on the size of polymer molecular coils.There is little difference in the aggregation morphology at different temperatures,all of which are sheet-like structures.Under acidic conditions,the size of polymer molecular coils is relatively large,and under alkaline conditions,the size of molecular coils is relatively small,and does not change significantly with the change of p H value.Under acidic conditions,the polymer aggregated form of polymer presents a rosary-like structure,while under alkaline conditions it transforms into a sheet-like structure.There is no linear relationship between salinity and particle size of polymer molecular coils.When the sodium chloride concentration is low,the polymer aggregates form worm-like structure,and when the sodium chloride concentration is high,it turns into sheet-like structure.Different kinds of salts have different effects on the size of polymer molecular coils,and Fe³⁺significantly increases the size of molecular coils.When different kinds of salts in the water,the aggregation morphology of the polymer are obviously different.3.The application of small-angle scattering(SASX)in polymer aggregation behavior is initially discussed.The experimental results show that the aggregation form of polyacrylamide molecules in the solution is spherical structure,with rotation radius of 8.68nm and Dmax of 25 nm,which is in good agreement with the data obtained by laser light scattering and TEM.It can be seen that it is feasible to extend the application of small-angle scattering technology to the study of polymer aggregation behavior.