Shear Viscoelasticity And Microscopic Percolation Characteristics Of Oil-Water Interface Of Different Types Of Polymers

At present,polymer and heavy oil activator flooding has entered the stage of industrial production and application.Preliminary results show that heavy oil activator flooding is better than ordinary polymer flooding.This may be related to the nature of the oil-water interface between the heavy oil and the polymer.By studying the rheological properties between the interfaces of oil and water,the formation and structure of the oil-water interface film during the chemical displacement process can be obtained,and then the interface phenomenon and the mechanism of enhanced oil recovery during the displacement process can be better explained.In order to investigate the effects of chemical flooding agents on the oil-water interface properties of crude oil and the displacement of residual oil,a three-component separation method was used to separate heavy oil from a Bohai Oilfield into asphaltenes,colloids,and the remaining.Based on that,the interfacial shear viscoelasticity between three kinds of chemical oil displacement agents at different concentrations(polyacrylamide,hydrophobic associative polymer APP4,heavy oil activator)and simulated oil(asphaltenes,colloids,and remaining components)were tested separately.Furthermore,through microscopic visualization of the oil displacement device,the microscopic percolation characteristics of the oil displacement agent were studied.The results show that the interfacial shear viscoelasticity between asphaltene simulated oil and chemical agents is the strongest,followed by colloidal simulated oil,and the remaining component simulated oil is the weakest.As the concentration of the chemical agent increases,the amount of active components adsorbed at the oil-water interface increases,and the interfacial shear viscoelasticity increases accordingly.Among them,the heavy oil activator contains active groups,which easily form hydrogen bonding with heavy oil components.Therefore,the strength of the interface film between the heavy oil activator and the heavy oil component is the largest,and the shear viscoelasticity is also the largest.APP4 contains hydrophobic groups,and can also form hydrogen bonds with heavy oil components to enhance the strength of the interface film,but that is weaker than heavy oil activators.Polyacrylamide contains no active groups,and has the weakest interaction with heavy oils,therefore,it has the smallest interface shear viscoelasticity.Microscopic displacement results show that heavy oil activators have the advantages of both surfactants and polymers.On the one hand,the residual oil is emulsified into oil droplets and extracted by emulsification,and on the other hand,the residual oil is "pulled" out by viscoelasticity.During the displacement process,not only the washing area is increased,but also the washing efficiency is improved.The hydrophobic associative polymer APP4 and the conventional polymer polyacrylamide displace the residual oil mainly through viscoelasticity.Studies have shown that under the same order of magnitude of interfacial tension,the higher the interfacial shear viscoelasticity,the stronger the interaction between oil and water,and the more obvious the effect of the chemical agents on the residual oil's transportation.Therefore,the displacement effect will be better.