Synthesis And Performance Evaluation Of Polyacrylamide Gel Microspheres Profile Control And Displacement Agent

In the middle-later development period of oilfield,the land has been scoured by water many times,so the stratum structure changes and presents heterogeneity.The land shows large pore and high permeability zone,which has serious impact on further oil exploitation.At present,deep water plugging and profile control technology has been developed rapidly for improving formation heterogeneity.In this paper,novel polymer gel microspheres has been prepared,and the performance of profile control and flooding is evaluated.In this study,two polymerization methods were used to prepare polyacrylamide gel microspheres with different particle sizes,for deep plugging to different formation environment and pore throat size.(1)Preparation of polyacrylamide nanomicrospheres with particle size of 50-100nm by inverse microemulsion polymerization;(2)preparation of polyacrylamide microspheres with particle size of 15?m-140?m by inverse suspension polymerization.Polyacrylamide nanomicrospheres prepared by inverse microemulsion polymerization method,the combination and dosage of emulsifier is important for the stability of the emulsion and reaction process.By drawing the three phase diagram of oil phase,water phase and emulsifier,the boundary of microemulsion was found.The result of this experiment shows that the polymerization of acrylamide is a typical free radical polymerization,which meets the characteristics of "slow initiation,rapid growth,and rapid termination" of free radical polymerization.The polyacrylamide gel microspheres have high thermal stability and begin to decompose after 300°C,which meet the oil reservoir application environment.The swelling property of microspheres in mineralized water is the key index to achieve formation fracture plugging.The polyacrylamide nanomicrospheres have the characteristics of slow expansion in the mineralized aqueous solution of 1OOOOOmg/L.After 10 days the equilibrium state is basically reached,and the expansion ratio is about 2.66.As the microspheres are used in the formation environment,the microspheres are always under the shear effect of the injected water.Therefore,the rheological behavior of the microspheres is of great significance to the study of the distribution of microspheres.The shear rheological properties of the gel microsphere solution are studied.The results show that the rheological properties of the polyacrylamide gel nanospheres are different from those of the ordinary polymer solution.The shear viscosity decreases first and then increases with the increase of the shear rate,and there is a critical shear rate(yc).Besides,the gel microsphere solution also has good viscoelastic properties.In this paper,the particle cluster theory of nanoparticles is used to model the rheological behavior of polyacrylamide microspheres under shear force.Micron-size polyacrylamide gel microspheres were prepared by reverse phase suspension polymerization.The effects of reaction temperature,stirring speed,dosage of initiator and solid contetemperature nt on the polymerization system were investigated,and the properties of resistance,salt resistance and plugging were evaluated.The experimental results show that the optimum reaction temperature of the system is 40-50 °C,the optimum stirring speed is in the range of 360-420 r/min,the amount of initiator can not be higher than 11%,the optimum dosage of emulsifier is 0.1%-0.4%,and the solid content is less than 25%.Besides,the micron-size polyacrylamide gel microspheres prepared by reverse phase suspension polymerization have high temperature resistance,salt resistance and plugging performance.