The real sandstone micromodel was used to perform an experiment of microscopic waterflooding in Chang-6 reservoir with low permeability in Ansai oilfield

Ordos Basin. Based on the experiment and the in-depth analysis of thin section observation

physical property

SEM

relative permeability and mercury injection data

we studied the relationship between pore structure and micro-flow characteristics of waterflooding

which provide a scientific basis for effective oil exploitation in the future. The study shows that the lithology of reservoir is mainly fine-grained arkose with low compositional maturity; there are three major pore types including resid- ual intergranular pore

dissolved pore and dual pore+fracture

of which the residual intergranular pore is dom- inant; Dissolved pore and fracture are the key factors influencing the micro-heterogeneity. The experiment results indicate that there are homogeneous

reticular and finger-like micro-flows. Pore structure is closely related with micro-flow features. Reservoirs with different pore types show different micro-flow features. Flow paths of injected water depend on the relative permeability of pores and fractures in zones with well-developed fractures. Pore structure heterogeneity and wettability are the two main factors influencing displacement efficiency.