Study On Viscoelastic Displacement Mechanism Of Tracer Fluorescent Polyacrylamide Microspheres

With the wide application of deep profile control and oil displacement technology of polymer microspheres and the continuous research of viscoelastic fluids,it is necessary to further deepen and clarify the effects of viscoelastic properties of polymer microspheres in oil displacement.The viscoelastic displacement mechanism of polymer microspheres was clarified by means of different viscoelastic fluorescent polymer microspheres.Polymer microspheres with fluorescent properties were synthesized by introducing fluorescent monomers and reaction conditions were optimized,and microspheres were characterized by molecular structure,micromorphology,fluorescence characteristics,particle size distribution and viscoelasticity.The swelling properties of microspheres were evaluated by volumetric method.The effects of temperature,p H value,salinity,polymer concentration and microsphere concentration on fluorescence intensity were studied.The determination curve of microsphere concentration was obtained.Through microscopic visualization of displacement,sand pack displacement experiments and microsphere concentration tests,the mechanism of microspheres' viscoelasticity in displacement was studied.The results show that the polymer microspheres with green fluorescence properties can be successfully obtained by introducing fluorescein.The polymer microspheres with different viscoelasticity can be obtained by varying the amount of crosslinker.The swelling ratio of fluorescent polymer microspheres increases with the increase of time and temperature.The swelling ratio of fluorescent polymer microspheres is relatively stable in the p H range of conventional reservoir conditions and the swelling ratio decreases rapidly with the increase of salinity.The fluorescence intensity of microspheres will decrease with the increase of temperature and p H.The fluorescence intensity is less affected by formation water ions,moreover,swelling time and polymer concentration exert negligible effect on fluorescence intensity.In the low concentration range,the fluorescence intensity of microspheres shows a good linear relationship with microsphere concentration,and the standard detection curve of microsphere concentration in produced liquid can be obtained.During the process of profile control and displacement,the elasticity of microspheres will dominate the migration mode of microspheres in the pore throat.The microspheres with higher elastic in piston migration mode have a higher sweep coefficient,and microspheres achieve deep profile control and improve the sweep coefficient by selectively blocking the pore throat and continuous deformation migration.The pushing and carrying effect of microspheres on the residual oil droplets,the positive pressure breakthrough effect formed by the microsphere trapping and the filling of the blind end to drive out the blind end immovable oil can improve the washing efficiency of microspheres.From the perspective of force analysis,it can be known that it is the elasticity of microspheres that plays the key role in the process of improving the sweep coefficient and washing efficiency of the microspheres.