The Influence of Mineral Texture on Fracture Geometry in Layered Geo-Architected Rock

Abstract

Rock is a complicated material because of the inherent heterogeneity in mineral phases and composition, even when extracted from the same rock mass. The spatial variability in compositional and structural features prevent reproducible measurements of deformation, fracture formation and other physical and chemical properties. Here, we use geo-architected 3D printed synthetic gypsum rock to show that mineral texture orientation governs the isotropy or anisotropy in fracture surface roughness and volumetric flow rate through tensile fractures. Failure load is governed by the orientation of depositional layering relative to loading direction but this effect can be hidden when an orientated mineral texture is present within the layers. We find that samples with certain mineral orientations are twice as strong as the weakest samples and that high values of sample strength correlate with rougher fracture surfaces. Mineral texture oriented parallel to the failure plane gives rise to anisotropic surface roughness and in turn to anisotropic flow rates. The uniqueness of induced fracture roughness and the degree of anisotropy is a potential method for assessment of the orientation and relative bonding strengths of minerals in a rock. With this information, we will be able to predict isotropic or anisotropic flow rates through fractures which is vital to induced fracturing, geothermal energy production and CO2 sequestration.