QUANTITATIVE VISUALIZATION OF ENTRAPPED PHASE DISSOLUTION WITHIN A HORIZONTAL FLOWING FRACTURE

An experiment was conducted to demonstrate the utility of quantitative fracture flow visualization techniques in the study of entrapped flui d phase (air) dissolution into a flowing phase (water) within a horizo ntal, transparent, analog rough-walled fracture. The fracture aperture field and phase occupancy were measured using light transmission tech niques and then combined to calculate bulk water-phase saturation with in the fracture as a function of time. Fracture relative permeability as a function of water-phase saturation showed a smooth power law beha vior during dissolution. Periodic step pulses of clear water within th e dyed water inflow yielded dye concentration fields that demonstrate channeling induced by the entrapped air phase. Clusters of the entrapp ed air-phase exhibited three types of dissolution behavior: general sh rinkage, interfacial recession along cluster appendages, and cluster s plitting. Locations for the advance of the wetting phase (water) into a nonwetting entrapped air cluster on its dissolution are not always c orrelated with either zones of high mass transfer rate (as inferred fr om gradients in the pulsed dye concentration fields) or with narrow ap ertures where the wetting phase has been thought to most easily invade . These results suggest that within an individual cluster of the entra pped phase, fluid pressure is at equilibrium and that the path of clus ter shrinkage may be controlled primarily by capillary forces resultin g from the full three-dimensional curvature that minimizes surface ene rgy of the phase interface.