In recent years, with the continuous improvement of oilfield development, medium–low permeability reservoirs have become the main target layers for oilfield development. These reservoirs possess abundant reserves, but they are characterized by poor physical properties and complex gravel structures, resulting in low water flooding recovery efficiency. Currently, polymer flooding is primarily used to enhance their production. To clarify the pore structure of medium–low permeability reservoirs under different permeability conditions and to investigate the fluid mobilization by polymer flooding in such reservoirs, this study conducted injectivity tests on six cores with different permeabilities to systematically evaluate the seepage characteristics of polymers in these cores. Furthermore, to better reveal the flow behavior of polymers in the cores, high-pressure mercury intrusion tests were employed to characterize the pore structure of the low–medium permeability reservoir cores. Constant-pressure displacement experiments were also performed, combined with nuclear magnetic resonance tests before and after polymer flooding, to explore the fluid mobilization in pores of different sizes during polymer flooding. Finally, a relationship chart between permeability and the microscopic accessible pore volume correction factor was established. The results indicate that cores with better permeability exhibit superior internal pore conditions and a lower limit of accessible pore size. Permeability shows a positive correlation with the microscopic accessible pore volume correction factor.
Zhang et al. (Sat,) studied this question.