Water-oil distribution and wettability within reservoir core, at both initial water saturation (S_wi) and residual oil saturation (S_or), can be replicated and subsequently viewed in individual pores within thin sections. The technique is applicable to native-state and restored-state cores.

Styrene monomer is used to miscibly displace oil and, following solidification, water is removed under vacuum. Then, sites formerly occupied by water are injected with epoxy resin. Fluorescent and non-fluorescent dyes are used in the styrene and epoxy for easy recognition in thin section. Experiments in glass micromodels confirm that these substitutions of styrene for oil and epoxy for water can be accomplished without altering wettability or water-oil distribution within a porous structure. The amount, distribution, and wettability of water and oil within reservoir core provides information useful in understanding water-oil relative permeability and displacement efficiency and is important in assessing production strategies for residual oil.