Effects of Gravity on Foam Behavior in Roughened Model Fractures

Summary In this study, to investigate how gravity affects foam in open vertical fractures, we report experiments three 1-m-long, 15-cm-wide glass-model fractures. Each fracture has a smooth wall and roughened wall. Between the two walls is slit-like channel representing single geological fracture. Three model fractures (Models A, B, C) share same roughness have different hydraulic apertures of 78, 98, 128 µm, respectively. We conduct by horizontal injection placed horizontally sideways (i.e., with turned on their long side), Model A vertically upward or downward. Direct imaging inside facilitated using high-speed camera. find that reaches local equilibrium (LE; where rate bubble generation equals destruction) horizontal-flow all vertical-flow A. larger aperture, coarser because less in-situ generation. properties are downward flow. Compared flooding, flooding creates finer-texture foam, as sections near inlet experiment wetter state, which benefits Moreover, gas trapped during gravitational potential helps overcome capillarity moves bubbles upward. sideways-flow experiments, segregation takes place. As result, drier propagates along top bottom. The more significant aperture. At quality 0.8, saturation 27.7% greater at than bottom for C, 19.3% 10.8% Models B Despite water not completely segregated. All thus represent capillary transition zone, increasing Our results suggest propagation natural meters tall tens long, an aperture hundreds microns greater, problematic. Gravity would weaken its capacity field maintain uniform flow divert over large distances.