Abstract: The polymer elastic microsphere of sub-micron grade is characterized by improving the waterflood sweep efficiency through its migration in pores, blocking-up leakage layer and changing injected water direction in reservoirs. This paper presents such a polymer features in water injection profile modification and its taking water and expanding properties in different salinities and temperatures as well as the blocking-up effects in sand-packed pipe. The lab study shows that the higher the temperature, the lower the salinity, the larger the times of polymer microsphere expansion. Also, injecting the polymer microspheres can distinctly improve the coefficient of resistance, that is, the higher the concentration of polymer microsphere, the bigger the injection rate of it, the higher the injection pressure. For the succeeding water injection stage, the higher residual coefficient of resistance could be remained by means of this process.

Key words: polymer, sweep efficiency, profile modification, oil recovery