Study On Rheological Property Of Linked Polyvinyl Alcohol(PVA) Aqueous Solution System

Up to now,most of the domestic oilfield development has entered the middle or late stage.The water content of produced fluid is usually as high as 90%.Homever,there are still a large number of heterogeneous reservoirs in the formation which have not been effectively exploited.Linked polymer solution is a dispersion system of linked polymer linear clusters in aqueous solution,which is produced by intramolecular crosslinking of partially hydrolyzed polyacrylamide with aluminum citrate at low concentration.The linked polymer thread are easy to be compressed and deformed,and block the pore throat by bridging.However,the concentration of the system generally does not exceed 300mg/L,which leads to low injection efficiency and large injection volume of the linked polymer solution.Polyvinyl alcohol can form a stable crosslinked polymer solution with the crosslinker at a concentration of dozens of times of polyacrylamide.So it has the possibility of being modifying and flooding agent.In this paper,crosslinked polyvinyl alcohol aqueous solution was prepared.The following results are obtained : influencing factors,particle size distribution,rheological property and plugging ability of the system.The performance of cross-linked PVA solution system is affected by many factors.The higher concentration,polymerization degree,crosslinking ratio and alcoholysis degree,the higher viscosity of the system.The higher temperature and salinity,and the lower viscosity of the system.The concentration and polymerization degree of PVA,crosslinking ratio have the most obvious influence on the performance of the system.When the concentration of PVA exceeds 20000 mg/L,the performance of the system changes greatly.The particle size of crosslinked polyvinyl alcohol solution in different concentration,different crosslinking ratio and different polymerization degree is detected by laser particle size analyzer.The detection result shows that the peak of particle size in the crosslinked polyvinyl alcohol solution is between 11 and 12 nm,the particle size is mainly distributed between 10 and 56 nm,and a small portion is distributed above 300 nm.And the greater the concentration,cross-linking ratio and PVA polymerization degree is,the larger the particle size get.Scanning electron microscope is used to observe the characteristics of the cluster,which was basically consistent with the results of laser particle analyzer.When the concentration and the crosslinking ratio of the system is larger,it will get better elasticity.The influence of the degree of polymerization on the elasticity of the system changes with the degree of concentration.At lower concentration,the greater the degree of polymerization is,the worse the elasticity of the system is.At higher concentrations,the greater the degree of polymerization is,the better the elasticity of the system is.For low concentration system,as the shear rate increases,the system exhibits newtonian fluid characteristic.When it increases to a certain value,the system will transform into dilatant fluid.For higher concentration system,the rule will change significantly;The crosslinking ratio and polymerization degree have relatively little influence on the flow curve of system.The system can effectively block the filter membrane within a certain range of concentration,crosslinking ratio and polymerization degree.And when the concentration,crosslinking ratio and polymerization degree are larger,the ability of blocking will be stronger.When the concentration reaches 20000mg/L,intermolecular crosslinking begins to occur in the system,which greatly improves its blocking performance.