Study On Profile Control Mechanism Of Low Elastic Polymer Microspheres

With the development of gel profile control system,the deep profile control technique of polymer microspheres has become a widely used new technology in improving the effeciency of water flooding and polymer flooding in heterogeneous reservoirs.To solve the problems of poor injection and deformation as well as easily broken after swelling of industrialization microspheres,we propose a low elastic polymer microsphere profile control system,consisting of polymer microspheres with low elastic modulus serving as the dispersed phase and partially hydrolyzed polyacrylamide(HPAM)solution as the dispersion medium,the system has good shearing resistance.The low elastic polymer microsphere profile control system displays good adaptability in high temperature and salinity heterogeneous oil reservoir.The low elastic polymer microsphere profile control system is thereby a kind of deep flooding technology with wide application prospect.A method for measuring the viscoelastic properties of viscoelastic microspheres based on bulk gel and the classification criteria of different viscoelastic microspheres were proposed.Based on the proposed method and the classification criteria,the kinetic equation of gel time of polymer microspheres bulk gel and reaction temperature was established.Starting from the molecular structure,using the optimized formulation of bulk gel as the aqueous phase,a series of low elastic polymer microspheres with controllable diameter were synthesized by inverse suspension polymerization.The factors that influence the low elastic polymer microsphere swelling properties were investigated by using swelling ratio as an evaluation index.In addition,the water absorption kinetic equation of low elastic polymer microsphere was put forward.The theoretical chart for swelling ratio of low elastic polymer microsphere was presented as well.By controlling the synthesis conditions and environmental factors,the initial particle size and swelling property of the low elastic polymer microspheres were further controlled.The stability evaluation standard of low elastic polymer microsphere profile control system was established.Meanwhile the growth in diameter and microscopic migration characteristics of microsphere in low elastic profile control system were researched.A kind of low elastic polymer microsphere profile control system with well stability was optimized.The regulatory factors of viscoelasticity of low elastic polymer microsphere profile control system were proposed.Using the "cluster" theory,the mechanism of shear thickening and the energy dissipation behavior of the system were revealed.Studies have shown that low elastic polymer microspheres profile control system at high shear rates can easily form a "cluster",exhibiting shear thickening behavior;the dissipation energy increases with the increase of the shear angle frequency.The quantitative corelation between the performance parameters of low elastic polymer microspheres and the pore throat size and the crack width were established.The migration mechanism in porous media was described.There are five ways for the migration of low elastic polymer microspheres in porous media: deformable passing through,partition passing through,blocking,adhesion and directly passing through.The water plugging rate is greater than the rate of oil in the same permeability cores.The low elastic polymer microsphere profile control system cause less damage to the low permeability layer,displaying good effects of selective profile control and turning fluid direction capability.For the higher permeability ratio,the better profile improvement effect when the high permeability layer was fixed.The research could provide a good theoretical guidance and technical support for the development of low elastic polymer microspheres profile control system application.