Stable drainage in a gravity field

During drainage, as a voxel of porous material is being actively invaded prior to percolation, the invading nonwetting fluid cannot be transmitted neighboring downstream until critical saturation (Snc) reached. This occurs when forms percolating path across voxel. We present novel laboratory observations gravitationally stable, air/water drainage in thin bead packs, with 2D fields monitored at high spatial and temporal resolution using light. also Invasion Percolation simulations. Both show that Snc has strong dependence on capillary number (Ca), Bond (Bo), size (Lz). propose percolation model describes functional form Snc(Bo,Ca,Lz). produce new theoretical for macroscopic pressure function Pc(Sw,Bo,Ca,Lz), where Sw wetting