Visualization of fluid occupancy in a rough fracture using micro-tomography.

The purpose of this work is to study the effects of fracture morphology on the distribution and transport of immiscible fluid phases, such as oil and water, through a vertical fracture. An experimental approach, using micro-computed tomography (MCT), was selected to characterize the internal fracture structure and to monitor two immiscible phases. The experiment was performed in Berea sandstone cores with a single longitudinal fracture. The artificially created fracture was oriented parallel to the natural bedding of the rock. The sample was initially vacuum-saturated with water, and oil was later injected through the longitudinal crack. Fluid occupancy in the fracture was mapped under four different flowing conditions: continuous oil injection, continuous water injection, simultaneous injection of oil and water, and a static pseudo-segregated state. Some of the mechanisms observed in this experiment include fluid trapping, preferential flow paths, snapping-off of non-wetting fluid globules, and coalescence and redistribution of globules between dynamic and static conditions. Experimental results indicate that distribution was mainly determined by fracture geometry, saturations, and wetting characteristics of the rock. A strong correspondence between fluid distribution and fracture apertures was found through direct comparison of two- and three-dimensional fracture structures.