Anisotropy in Element Composition and Pore-size Distribution of Mudstones

Mudstones consist of fine-scale layering of sediments which can contribute to anisotropy in their hydraulic behavior ranging over several order of magnitudes. Anisotropic hydraulic behavior of mudstones is likely due to anisotropy in pore-size distribution and mineral composition related to burial geohistory specific to a depositional environment. How anisotropic variations in pore-sizes and mineral composition control the hydraulic behavior of mudstones is not well understood. In this study, we quantify anisotropic variation in element and pore-size distribution of mudstone rocks. We use SEM-EDS to take multiscale high resolution images representative of each anisotropic direction, i.e., vertical and horizontal to sediment layering. These images are segmented using digital rock physics to obtain pore-size and element distributions representative of each anisotropic direction. Finally, XRD analysis is conducted to identify mineral composition of sample to help reference the likely presence of minerals from elemental maps obtained via SEM-EDS. Findings from this research will help us better understand how naturally occurring fine-scale layering in mudstones likely control anisotropy in hydraulic and membrane properties. These findings may bear implications for the subsurface investigations of contaminant storage and transport, geohazards, and hydrocarbon recovery.