While research on multiphase flow in porous media has been very extensive in the last 40 years, at both the pore and continuum scales, comprehensive understanding of how the phe- nomenology of two-phase flow in geological fractures is impacted by both the flow conditions (capillary number Ca and viscosity ratio M ) and the geometry (fracture closure), remains elu- sive. We investigate residual trapping of CO2 in fractured reservoirs at the fracture scale, explor- ing the complex interplay between fracture surface roughness and the displacement of fluid-fluid interfaces. Our systematic approach explores the phenomenology of two-phase flow in fractures, taking into meticulous consideration the fluid properties, flow conditions, and fracture geometry. To this aim, we have developed a transparent fracture flow cell with self-affine rough-walled sur- faces and precisely-controlled mean aperture, which can be varied. The fracture wall geometry is generated from numerical models that are consistent with the well-known stochastic geometric properties of geological fractures. A camera allows recording the dynamics of the fluid phases' spatial distribution within the fracture plane. The displacement patterns are characterized as functions of Ca, M , the density difference of the fluids, and the fracture's geometrical parameters. We thus aim to characterize the amount of supercritical CO2 trapped in fractured aquifers as a function of those controlling parameters.