Understanding the transport of three fluid phases through porous media has important applications in subsurface contaminant remediation, oil and gas recovery, and geological CO₂ sequestration. Existing transport models may be improved by including physical phenomena that govern fluid flow at the pore scale. In particular, thermodynamic arguments suggest that hysteresis...
This research examines the independent and combined effects of drainage and imbibition flowrate on nonwetting phase capillary trapping in a two-phase, porous medium system. A uniform system of cubic arrangement and non-uniform systems of both cubic and rhombohedral arrangements were examined in order to analyze and compare the nonwetting phase...
Geologic CO₂ sequestration is a climate change mitigation strategy that involves the injection of supercritical CO₂ into deep underground rock formations. This thesis focuses on capillary trapping in which capillary forces immobilize CO₂ bubbles at the pore scale. During injection of supercritical CO₂, brine is displaced in what is known...
Multi-phase flow in porous media includes many instances of subsurface flow. Three-phase flow in particular is important in situations of enhanced oil recovery, CO2 sequestration, and groundwater remediation. Many studies have been performed on how two fluid phases (oil/water or air/water) behave in porous media, but very few studies exist...
Systems that contain multi-phase flow in porous media are of interest in diverse fields including environmental engineering, hydrogeology, and petroleum engineering etc. One of the main descriptors of multi-phase flow in porous media is the relationship between capillary pressure and fluid saturation. Capillary pressure is inherently a pore-scale variable and...
This work examines the impact of a viscosity force parameter, fluid velocity, and a capillary force parameter, interfacial tension, on the saturation, morphology, and topology of NW fluid in Bentheimer sandstone after primary imbibition, drainage, and secondary imbibition. Brine and air (used as a proxy for supercritical CO₂) flow experiments...
The flow of multiple immiscible fluids within a porous medium controls many natural and engineered systems in the environment including: geologic CO2 sequestration, enhanced oil recovery from underground reservoirs, and contaminant remediation of groundwater. The need to understand how fluids are transported and distributed in these processes is important for...
The wetting of a surface by a liquid is a crucial part of many natural and industrial processes. Despite numerous existing studies, some elements of wetting-dewetting such as contact angle variation are still poorly understood. Knowledge of contact angle behavior during the flow is necessary for modeling fluid displacements in...
Geologic CO₂ sequestration is a climate change mitigation strategy that prevents CO₂ emissions to the atmosphere by capturing CO₂ gasses from large point source emissions streams and then pressurizing and pumping the supercritical-state CO₂ into underground geologic storage reservoirs. Once underground, CO₂ is prevented from buoyant migration to the surface...
Engineered capillary barriers typically consist of two layers of granular materials designed so that the contrast in sediment hydrologic properties and sloping interface retains infiltrating water in the upper layer. We report here on the results of two bench-top capillary barrier experiments, and associated modeling. These experiments were conducted to...
Understanding the mechanisms controlling colloid transport and deposition in the vadose zone is an important step in protecting our water resources. Colloid transport in unsaturated porous media was studied using X-Ray Microtomography (XMT), which is a non-destructive imaging technique that provides three-dimensional images at a resolution on the order of...
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Dorthe Wildenschild
Understanding the mechanisms controlling colloid transport and
Current oil production technologies recover only about one‐third to one‐half of the oil
originally present in an oil reservoir. Given current oil prices, even a modest increase in oil recovery efficiency is fiscally attractive. One novel approach to increase oil recovery
efficiency is a process called microbial enhanced oil recovery...
Recent advances in imaging technology and numerical modeling have greatly enhanced pore-scale investigations of multiphase flow and transport in porous media. It is now feasible to obtain high resolution 3-dimensional pore-scale data, and numerical methods such as the lattice-
Boltzmann (LB) technique have been developed specifically for simulating such phenomena....
Atmospheric carbon reduction is arguably the most crucial facet among efforts to mitigate climate change. The Fifth International Panel of Climate Change report emphasizes a worldwide goal of maintaining global temperature elevation less than 1.5°C above pre-industrial temperatures. This report also acknowledges without the proper utilization of counteractive emission strategies...
Rising CO₂ concentrations in the atmosphere (396 ppmv as of April 2012)
increase the effect of global warming and climate change. CO₂ sequestration has become
a potential method to mitigate climate change. This study focuses on capillary/residual
trapping as a form of geologic CO₂ sequestration. Capillary/residual trapping occurs
when supercritical...
Geological carbon sequestration, as a method of atmospheric greenhouse gas reduction, is at the technological forefront of the climate change movement. During sequestration, carbon dioxide (CO₂) gas effluent is captured from coal fired power plants and is injected into a storage saline aquifer or depleted oil reservoir. In an effort...
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Dorthe Wildenschild
Geological carbon sequestration, as a method of atmospheric greenhouse
Use of basalt aquifers for aquifer storage and recovery (ASR) systems is increasing in the Pacific Northwest due to the large aerial extent of the Columbia River Basalt Group and the suitability of basalts as ASR reservoirs. However, the degradation of trihalomethanes (THMs), potentially carcinogenic disinfection by-products present in the...
Microbial Enhanced Oil Recovery (MEOR) is a process where microorganisms are used for tertiary oil recovery. Numerous mechanisms have been proposed in the literature through which microorganisms facilitate the mobilization of residual oil. Herein, we focus on the MEOR mechanisms of interfacial tension reduction (via biosurfactant) and bioclogging in water-wet...
We report here on recent developments and advances in pore-scale x-ray tomographic imaging of subsurface porous media. Our particular focus is on immiscible multi-phase fluid flow, i.e., the displacement of one immiscible fluid by another inside a porous material, which is of central importance to many natural and engineered processes....
This work focuses primarily the development of methods for imaging microbial biofilms in opaque porous media using x-ray computed microtomography (CT). Two methods for evaluating biofilms in porous media are presented. The first focuses on the addition of silver-coated, hollow glass microspheres to a biofilm-containing micro-model. The silver-coated microspheres affix...
Engineered capillary barriers typically consist of two layers of granular materials designed so that the contrast in material hydraulic properties and sloping interface retain infiltrating water in the upper layer. We conducted two benchtop capillary barrier experiments, followed by interpretation and numerical modeling. The hydraulic parameters for two coarse materials...
Heterogeneous porous material represents a persistent challenge in the field of engineering. Microscale properties such as the porosity and microchannel torturosity significantly control the macroscale transport characteristics of homogeneous porous medium. Additional complexity is introduced when these small-scale features vary in space. Examples of heterogeneous porous systems include artificial body...
The objective of this study is to investigate the dispersion of solute matter introduced into a fully developed laminar flow in a circular capillary tube under preasymptotic regimes. For this purpose, we have used the method of volume averaging to upscale microscale balance equations for the case of diffusion-convection transport...
This work is an attempt to develop a simple physical description for the initial
interactions between a bacterial cell and a substrate surface. This is done by
adopting a view that regards bacterial surface biomolecules not as secondary and
add-on contributors to the potential energy function that characterizes the
overall...
Understanding the transport and retention of radionuclides in the environment is important for protecting freshwater supplies and minimizing impact to biologic systems. Technetium-99 (Tc⁹⁹) is a radionuclide of interest due to its long half-life (2.13 x 10⁵ years) and toxicity. In the form of pertechnetate (TcO₄⁻), Tc is expected to...
Elevated groundwater nitrate (NO3
-) concentrations in the Southern Willamette
Valley (SWV) caused the Oregon Department of Environmental Quality (ODEQ) to
declare a Groundwater Management Area (GWMA) in Spring, 2004. To better
understand direction of groundwater flow, groundwater age, and nitrate transport
pathways of the SWV we developed a steady-state...
Colloids, particles smaller than ten microns in diameter, are ubiquitous in the subsurface. Colloids have an effect on the transport of contaminants that bind to their surfaces, and can reduce the permeability of aquifer materials through deposition. Some microorganisms, including pathogens, are also transported in the subsurface as colloids. The...
This work focuses on solute mass transport in a highly heterogeneous two-region porous medium consisting of spherical low-hydraulic conductivity inclusions, embedded in a high-hydraulic conductivity matrix. The transport processes occuring in the system are described by three distinct time scales. The first time scale reflects the characteristic time for convective...
Low-permeability geologic units may offer significant chemical and hydraulic protection of adjacent aquifers, and are important for managing groundwater quality, especially in areas with significant non-point source contamination. Nitrate in the Willamette Valley is attenuated across the Willamette Silt, a semi-confining unit overlying a regionally important aquifer. To quantify the...
Transport phenomena specially the ones that occur in the various engineering disciplines such as tissue engineering and natural environment are often complex to analyze mostly due to the dynamic and geometric complexities; as such, they have been the subject of an active and intense area of research in past decades....
Groundwater nitrate contamination is a well-documented issue in the Southern Willamette Valley (SWV) of Oregon, as a Groundwater Management Area (GWMA) has recently been declared. As a GWMA, groundwater nitrate monitoring must occur until regional concentrations are below 7 mg/L NO3-N. However, the presence of temporal variability can make it...
Metal and hydrogen ion acidity and extreme nitrate concentrations typical of
Department of Energy (DOE) legacy waste sites pose formidable challenges to
successful implementation of in situ bio-immobilization. Intermediate-scale (~ 2.5 m),
flow through models of an in situ bio-barrier were constructed to investigate U and Tc
removal from groundwater...
Easier access to X-ray microtomography (lCT) facilities has provided much new insight from high-resolution imaging for various problems in porous media research. Pore space analysis with respect to functional properties usually requires segmentation of the intensity data into different classes. Image segmentation
is a nontrivial problem that may have a...
This work utilizes synchrotron-based x-ray computed microtomography (x-ray CMT) imaging to quantify
the volume and topology of supercritical carbon dioxide (scCO₂) on a pore-scale basis throughout the
primary drainage process of a 6 mm diameter Bentheimer sandstone core. Experiments were performed
with brine and scCO₂ at 8.3 MPa (1200 psi)...
Abstract: Several models for two-phase flow in porous media identify trapping and connectivity of fluids as an important contribution to macroscale hysteresis. This is especially true for hysteresis in relative permeabilities. The trapping models propose trajectories from the initial saturation to the end saturation in various ways and are often...
Synchrotron-based tomographic datasets of oil–water drainage and imbibition cycles have been analyzed to quantify phase saturations and interfacial curvature as well as connected and disconnected fluid configurations. This allows for close observation of the drainage and imbibition processes, assessment of equilibrium states, and studying the effects of fluid phase disconnection...
The macroscopic description of the hysteretic behavior of two-phase flow in porous media remains a challenge. It is not obvious how to represent the underlying pore-scale processes at the Darcy-scale in a consistent way. Darcy-scale thermodynamic models do not completely eliminate hysteresis and our findings indicate that the shape of...
In order to better predict the aggregation state of nanomaterials, the factors that influence aggregation must be understood. The combined effects of natural and engineered coatings have been shown to factor into nanoparticle aggregation behavior in preliminary research. In this study, aggregation behaviors of gold nanoparticles with two different engineered...
The kinetics of physical and chemical processes controlling the precipitation of iron oxide minerals in unsaturated media were investigated in this study. The characteristic morphology, mineralogy, and chemistry of iron oxides were also explored. Laboratory column experiments using fine and coarse grades of silica sand were conducted to compare the...
Abstract Watershed-scale fate/transport modeling of contaminants is a tool that scientists and land managers can use to assess pesticide contamination to stream systems. The Catchment Modeling Framework (CMF) is a catchment-scale fate/transport modeling tool. It was developed to help scientists and land managers assess the effects of possible land-use decisions...
This thesis builds on a modeling tool that has been developed to link thermodynamic modeling and concrete performance. This tool is intended to predict the performance for modern concrete mixtures made with ordinary portland cement (OPC), conventional and novel supplementary cementitious materials (SCMs), and limestone (Ls). The first part of...
Microplastics, plastic marine debris less than 5 mm in size, is a threat to the health of our oceans. One important way to reduce microplastics in our oceans is to educate people about the issue, particularly future decision-makers. In this study, a middle school curriculum was developed using current scientific...
This thesis presents an experimental study of radial porosity in a manually filled cylindrical container with glass spheres. The symmetric distribution of bead diameter allowed for normalization of container properties and porosity models. The aspect ratio of the container was approximately 3.9, with tube-to-particle-diameter ratio λ ≈ 24.6 and height-to-particle-diameter...
This work is a compilation of problems that deal with multiscale analysis of transport phenomena in environmental systems. A common feature among the problems studied here is the presence of non-negligible microscale structure in various forms. Each problem is approached from the perspective that a macroscopic observable encodes aspects of...
In this work we consider two multiscale applications with tremendous computational complexity at the lower scale. First, we examine a model for charge transport in semicon- ductor structures with heterojunction interfaces. Due to the complex physical phenomena at the interface, the model at the design scale is unable to adequately...
In order to enable better visualization and understanding of the effect of the robot's geometry and inertia on the robot's trajectories, this dissertation proposes to use geometric mechanics to bridge the gap between the physical motion of a robot and its mathematical structure. The main focus of this research is...
Vortical structures are the driving mechanism of transition to turbulence in porous media requiring adequately resolved observations along with analysis of the scale and energy of flow within the pores. Of specific interest is to understand the vortex dynamics, energy, and turbulent mixing and transport properties in the scale of...
Forest roads produce fine sediment with traffic during wet weather. If the forest road is connected to a stream it can be a source of turbidity and fine sediment that may be detrimental to aquatic organisms especially salmonids.
The goal of this work was to investigate turbid runoff during wet-weather...
Despite more than two centuries of exploration, including more than six million deep wellbores with depths exceeding 40,000 feet in some parts of the world, our ability to constrain subsurface processes and properties remains limited. Characteristics of the subsurface vary and can be analyzed on a variety of spatial scales....
Interest in performance specifications has been growing in the civil and construction industry in the past decade. One major focus area has been on understanding how to prolong the service life of concrete structures, since repair and rehabilitation of existing infrastructure have cost many trillions of dollars. Deterioration mechanisms such...