Research On Synthesis And Profile Control Properties Of Pore-scale Polymer Microspheres

It is well known that the oil recovery is determined by the sweep volume and oil displacement efficiency of injection fluid. The oil fields in our country are featured with many layer series of development, in-layer and interlayer heterogeneity, low sweep efficiency and oil recovery. Improving the sweep efficiency is an important method to enhance oil recovery.The reservoir rock has complex pore structure. Based on the capillary model, calculated results show that the pore throat has micron scale properties. Its range of variation increases as the reservoir heterogeneity gets stronger, and macropore is an important reason of water fingering. The polymer elastic microspheres can not only protect low-permeability reservoirs, but also achieve to plug, deform and move in pores, turn flow direction in deep hypertonic reservoir and increase the sweep volume.This paper studies the synthesis and profile control properties of pore-scale polymer microspheres. Laboratory experiments show that two sizes series of polymer microspheres are composed by suspension polymerization in disperse medium according to the different permeability reservoirs. Then its basic physical and chemical properties, plugging character and migration behavior, profile control and displacement effect are studied. The results show that microspheres have good sphericity, temperature and salinity tolerance and good dispersion in water, which are swelled when absorbing water. The expansion ratio increases with the temperature and declines with the mineralization. The plugging and migrating behavior of the microspheres shows that it can be injected into cores easily, enhancing the flow resistance factor and improving injection profile. The injection pressure increases with the concentration and injection volume of microspheres. The flow residual resistance factor remains high during the post-flooding period. Local tests results show that the microspheres can decrease the flow velocity of high permeability zones, increase injection well pressure and decrease the reservoir heterogeneity. It can also increase oil and decrease water obviously in corresponding production wells, improving the effectiveness of water-flooding development.