Reservoir pore structure and micro-flow characteristics of waterflooding: a case study from Chang-6 reservoir of Wangyao block in Ansai oilfield

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.