Laboratory-based investigation into the fluid flow properties of natural and 3D-printed rough fractures

Low-permeability geological seals may be compromised by the occurrence of fluid-conductive fault and fracture systems, which can potentially transmit fluids away from the storage reservoir. We performed a systematic laboratory-based investigation into the effect of surface roughness on the fluid flow properties of both natural rock and 3D-printed fractures. The natural rock fractures span a range of lithologies and modes of creation. The synthetic fractures were numerically generated through accounting for complex matching properties and anisotropies within the defining properties of a fracture surface. A multipronged experimental approach was undertaken, comprising digital optical microscopy for roughness quantification, single-phase (core flooding) experiments for permeability evolution with effective stress, and X-ray micro-computed tomography (μ-CT) performed on 3D-printed fractures to investigate aperture field evolution during fracture closure. Results from this study provide further insights into the physical transport properties of fractures as a function of lithology, angle to bedding and surface roughness distribution. This work is used to directly inform caprock leakage models for a joint industry research project, which aims to generate guidelines for determining the risk of CO2 leakage along faults and fractures in low-permeability caprocks.