Visualization and quantification of single and multiphase flow in a rough fracture

Immiscible displacement of fluids across fractures with spatially variable aperture is key in several subsurface processes, including enhanced oil recovery and geological CO₂ sequestration. We illustrate the results of an experimental investigation campaign focused on qualitative and quantitative assessment of main features associated with single and multiphase flow in a single fracture, including, e.g., an appraisal of the geometrical parameters of the fracture and the distribution and dynamic characteristics of fluids.
Experiments are performed on fracture replicas reproduced from natural rock blocks, that are artificially split by steer wedges under normal load. Two fracture replicas are then considered, corresponding to (a) a sample molded with synthetic material after the rock sample and (b) the actual rock sample, respectively. This enables one to provide a first appraisal of the impact of the material constituting the wall of the fracture on the multiphase flow system behavior. A transparent upper wall is set in place to enable visualization.
Surface profiles of the fracture are collected, comprising a set of more than 400,000 data of aperture distribution to create a digital twin of the system. These data are first subject to detailed statistical characterization, including standard geostatistical and fractal-based approaches. Experimental data of flow are quantitatively correlated to the key statistical features characterizing fracture geometry under various flow rates and normal loading conditions. Temporal monitoring of fluid saturation distribution enable us to provide a preliminary assessment of the impact of the material constituting the fracture wall (e.g., in terms of its wettability) on fluid saturation distribution.