Abstract: Bohai Oilfield is characteristic of high porosity and high permeability, loose and fragile, strong heterogeneity. Some well groups have encountered the problems of low efficiency or ineffective circulation of injected water, accelerated water channeling and increased decline rate. Field application test shows that the new cross-linked polymer microsphere P-90 has better profile control and flooding effect for this type of reservoir. In order to better analyze and explain its profile control and flooding mechanism, scanning electron microscopy, laser particle size analyzer, high temperature and high pressure rheometer, microporous filter membrane device, one-dimensional physical model flow device, etc. are employed to evaluate the basic physical and chemical properties and profile control and flooding capability of P-90. The experimental results show that the new crosslinked polymer microsphere P-90 has good swelling effect. After hydration and swelling, a cross-linked spatial network structure is formed between the spheres. The particle size is evenly distributed and remains at 15 μm for a long time. It has good temperature resistance and viscosity retention rate; the membrane with pore size of 5 and 10 μm was effectively blocked. This new crosslinked polymer microsphere P-90 has both the crosslinked network structure of polymer gel and the spherical dispersion structure of polymer microspheres. Its unique microstructure has a significant improvement effect on heterogeneous high porosity and high permeability reservoirs. It has good injectivity, with greatly improved plugging and oil displacement efficiency, and can achieve better deep profile control and flooding effect.

Key words: crosslinked polymer microspheres, microporous membrane, deep profile control and flooding, enhanced oil recovery, high porosity and high permeability