Dynamic Migration Mechanism Of Nano-polymer Microspheres

In recent years,nano polymer microspheres have been widely used in low permeability and ultra-low permeability reservoirs.Nano polymer microspheres are widely used in many oilfields.In the process of field application,it is found that "the smaller the particle size of the microspheres,the better the effect of profile control and drive",which is contrary to the theory of profile control and drive matching the conventional particle size polymer microspheres with the formation pore throat.In order to study the mechanism of dynamic profile control and drive of nano polymer microspheres,the field profile control and drive law was explained theoretically.The physical and chemical performance evaluation experiment of nano polymer microspheres,physical simulation experiment of artificial core and sand filling pipe were carried out.The micro physical simulation experiment of etched glass was designed and implemented.Based on the indoor experiment results,the mathematical model of polymer microspheres for profile control and displacement was established by combining reservoir physics and porous media hydrodynamics theory,and the field application data was brought into the mathematical model for calculation and comparison The mechanism of nano polymer microspheres in low permeability and ultra-low permeability reservoir is determined.In this paper,through the study of physical and chemical properties,it is found that the nano polymer microspheres have good sphericity,the particle size obeys the extreme function,the volume of the microspheres can be increased to 7-10 times of the initial volume after water swelling,and have agglomeration characteristics.Nano polymer microspheres have good characteristics of profile control and drive.The smaller the particle size in the experimental range,the better the profile control and drive effect.The cumulative recovery degree of the injected 100 nm polymer microspheres is the highest,and the cumulative recovery degree of the low permeability layer reaches 60.6%,the experimental results are consistent with the field application law.Through the physical simulation experiment of single sand filled tube,it is found that the injection speed suitable for nano polymer microspheres is 0.5ml/min,which is the speed The lower multi-stage pressure data has synchronous change,and the nano polymer microspheres can stabilize in the middle and rear,and the recovery degree after deep profile control and flooding reaches 59.8%.Through the micro physical simulation experiment of etched glass,it is found that the nano polymer microspheres have the phenomenon of viscosity and adhesion on the inner surface of the pores,which has a stable additional resistance to the subsequent injected fluid.Based on the particle size distribution of nano polymer microspheres and the distribution of formation pore throat,six matching forms are proposed.The mechanism that the retention of nano polymer microspheres results in the partial diversion of fluid flow and the displacement of remaining oil is put forward.The phenomenon and law of the application of polymer microspheres in the field are explained reasonably combining with the mathematical model of changing the specific surface area in the pore throat.The research results of this paper provide the basis of parameter selection and basic research theory for nano polymer microspheres to improve oil recovery in low permeability and ultra-low permeability reservoir.