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How pore geometry affects the transition of non-Fickian to Fickian solute transport over various length scales

03/21/2019
Pore scale solute transport is known to exhibit non-fickian solute transport characteristics related to pronounced tailing during asymptotic times. The tailing behavior is likely associated with large variability in pore fluid velocity, which is caused by diverging-converging pore channel geometry, and which further is magnified during inertial flows, as eddies or ‘recirculation zones’ form and grow in the dead-end part of pore channels. In this study we, at first, design a series of pore channel geometries and define them with a non-dimensional pore geometry parameter ‘γ’. We use these geometries to solve Navier-Stokes and Advection-Diffusion (ADE) equations and obtain ‘break through curves’. These curves are used to fit analytical solution to ADE and determine the degree of non-fickian to fickian transport characteristics for various range of Reynolds number (Re) flows. Finally, pore channels are systematically extended in the direction of flow to ‘length scales’ where the non-Fickian transport becomes Fickian transport. The relationships between ‘γ’, Re, and length scales for Fickian transport will be presented during the conference meeting.
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Anisotropy in Element Composition and Pore-size Distribution of Mudstones

04/05/2018

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.
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Conference Proceeding