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Applied physics, Fluid dynamics, Petrol
Abstract:
Wettability is an important factor which controls the displacement of immiscible fluids in permeable
media, with far reaching implications for storage of CO2 in deep saline aquifers, fuel cells, oil recovery,
and for the remediation of oil contaminated soils. Considering the paradigmatic case of random
piles of spherical beads, fluid front morphologies emerging during slow immiscible displacement
are investigated in real time by X-ray micro–tomography and quantitatively compared with model
predictions. Controlled by the wettability of the bead matrix two distinct displacement patterns are
found. A compact front morphology emerges if the invading fluid wets the beads while a fingered
morphology is found for non–wetting invading fluids, causing the residual amount of defending fluid
to differ by one order of magnitude. The corresponding crossover between these two regimes in terms
of the advancing contact angle is governed by an interplay of wettability and pore geometry and can
be predicted on the basis of a purely quasi–static consideration of local instabilities that control the
progression of the invading interface.
