• 3D modeling and characterization of hydraulic fracture efficiency integrated with 4D/9C time-lapse seismic interpretations in the Niobrara Formation, Wattenberg field, Denver Basin

      Benson, Robert D.; Davis, Thomas L. (Thomas Leonard), 1947-; Alfataierge, Ahmed; Sonnenberg, Stephen A.; Miskimins, Jennifer L.; Trainor-Guitton, Whitney; Tutuncu, Azra (Colorado School of Mines. Arthur Lakes Library, 2017)
      Hydrocarbon recovery rates within the Niobrara Shale are estimated as low as 2-8%. These recovery rates are controlled by the ability to effectively hydraulic fracture stimulate the reservoir using multistage horizontal wells. Subsequent to any mechanical issues that affect production from lateral wells, the variability in production performance and reserve recovery along multistage lateral shale wells is controlled by the reservoir heterogeneity and its consequent effect on hydraulic fracture stimulation efficiency. Using identical stimulation designs on a number of wells that are as close as 600ft apart can yield variable production and recovery rates due to inefficiencies in hydraulic fracture stimulation that result from the variability in elastic rock properties and in-situ stress conditions. As a means for examining the effect of the geological heterogeneity on hydraulic fracturing and production within the Niobrara Formation, a 3D geomechanical model is derived using geostatistical methods and volumetric calculations as an input to hydraulic fracture stimulation. The 3D geomechanical model incorporates the faults, lithological facies changes and lateral variation in reservoir properties and elastic rock properties that best represent the static reservoir conditions pre-hydraulic fracturing. Using a 3D numerical reservoir simulator, a hydraulic fracture predictive model is generated and calibrated to field diagnostic measurements (DFIT) and observations (microseismic and 4D/9C multicomponent time-lapse seismic). By incorporating the geological heterogeneity into the 3D hydraulic fracture simulation, a more representative response is generated that demonstrate the variability in hydraulic fracturing efficiency along the lateral wells that will inevitability influence production performance. Based on the 3D hydraulic fracture simulation results, integrated with microseismic observations and 4D/9C time-lapse seismic analysis (post-hydraulic fracturing & post production), the variability in production performance within the Niobrara Shale wells is shown to significantly be affected by the lateral variability in reservoir quality, well and stage positioning relative to the target interval, and the relative completion efficiency. The variation in reservoir properties, faults, rock strength parameters, and in-situ stress conditions are shown to influence and control the hydraulic fracturing geometry and stimulation efficiency resulting in complex and isolated induced fracture geometries to form within the reservoir. This consequently impacts the effective drainage areas, production performance and recovery rates from inefficiently stimulated horizontal wells. The 3D simulation results coupled with the 4D seismic interpretations illustrate that there is still room for improvement to be made in optimizing well spacing and hydraulic fracturing efficiency within the Niobrara Formation. Integrated analysis show that the Niobrara reservoir is not uniformly stimulated. The vertical and lateral variability in rock properties control the hydraulic fracturing efficiency and geometry. Better production is also correlated to higher fracture conductivity. 4D seismic interpretation is also shown to be essential for the validation and calibration hydraulic fracture simulation models. The hydraulic fracture modeling also demonstrations that there is bypassed pay in the Niobrara B chalk resulting from initial Niobrara C chalk stimulation treatments. Forward modeling also shows that low pressure intervals within the Niobrara reservoir influence hydraulic fracturing and infill drilling during field development.
    • 4D processing and time-lapse azimuthal amplitude analysis using legacy surveys for Niobrara reservoir characterization, Wattenberg field, Colorado

      Davis, Thomas L. (Thomas Leonard), 1947-; Nurhasan, Abdullah; Tura, Ali; Simmons, James; Sonnenberg, Stephen A.; Prasad, Manika (Colorado School of Mines. Arthur Lakes Library, 2017)
      Understanding changes in reservoir properties with time due to hydraulic fracture stimulation and production is important. Time-lapse (4D) seismic data analysis enables investigation of stimulated and produced reservoir volumes and helps forecast reservoir performance. Time-lapse seismic has proven beneficial for monitoring conventional high porosity reservoirs but its application to unconventional reservoirs is still in its infancy. Monitoring unconventional reservoir properties relies on the investigation of the natural fracture network affected by stimulation and production. This study investigates the potential of legacy seismic surveys for time-lapse azimuthal anisotropy analysis in Wattenberg Field, Denver Basin, Colorado. A workflow for co-processing and methods of analyzing reservoir changes using legacy surveys is developed. The workflow and methods can be used in Wattenberg and potentially in other resource plays. The application of legacy 4D surveys to analyze unconventional reservoirs requires careful applications of cross-equalization for preservation of time-lapse amplitude changes. Despite the differences in acquisition geometries and parameters this study resulted in normalized root mean square (NRMS) differences of .28 or 28% in the overburden interval above the Niobrara. A widely accepted threshold of .30 or 30% is considered as a measurable index of excellent repeatability. Azimuthal amplitude variation analysis is used to detect the orientation of the isotropy plane. The azimuth of the isotropy plane indicates the dominant orientation of the fractures affecting seismic anisotropy. Fracture orientation does not always coincide with the maximum horizontal stress. A reduction in amplitude variation with azimuth is observed near faults and is postulated to be a result of multiple fracture orientations. This study provides new insight by illuminating fracture orientations that were not captured by microseismic data or image logs in horizontal wells. Time-lapse analysis in azimuthal amplitude variation shows anisotropy increases in the reservoir interval. The increase in anisotropy from baseline to monitor is interpreted as being caused by gas coming out of solution in the more fractured parts of the reservoir. Investigating changes in the azimuth and magnitude of anisotropy is beneficial for monitoring unconventional reservoirs.
    • Acceleration of finite difference time domain modeling using GPU and transfer functions with application to channel modeling

      Elsherbeni, Atef Z.; Diener, Joseph Elliot; Nayeri, Payam; Hadi, Mohammed; Quimby, Jeanne (Colorado School of Mines. Arthur Lakes Library, 2017)
      Next generation communication technologies aim to use broadband and/or high frequency systems for commercial communications, including utilizing mmWave frequencies and ultra-wide bands. Channel modeling at these frequencies is currently the focus of extensive measurement campaigns. Application of the Finite Difference Time Domain (FDTD) method at mmWave frequencies is suitable for modeling the broadband system, but several challenges remain between it and practical implementation. This thesis shows practical, simple GPU implementations suitable for FDTD modeling using MATLAB for accelerating large problems, such as those found at mmWave frequencies. Additionally, it’s shown that transfer functions can be utilized within the FDTD method to allow for simulation of arbitrary length signals within ordinary simulation times, that can achieve better than -30dB of error between transfer function and direct simulation approaches.
    • Actinide-aminopolycarboxylate complexation thermodynamics: americium, berkelium, californium, and einsteinium

      Shafer, Jenifer C.; Urban, Matthew; Deinert, Mark R.; Jensen, Mark; Vyas, Shubham (Colorado School of Mines. Arthur Lakes Library, 2017)
      Previous experiments revealed evidence for modestly selective interactions, encouraged by orbital degeneracy driven covalency, between berkelium and curium using the aromatic aminopolycarboxylate dipicolinic acid. To further probe the ability for the heaviest available actinides to participate in orbital degeneracy driven covalent interactions, solvent extraction competition investigations were completed with the late actinides americium, berkelium, californium, and einsteinium. These studies were completed with aliphatic aminopolycarboxylates (nitrilotriacetic acid, 2-hydroxyethyl ethylenediaminetriacetic acid, trans-1,2-cyclohexanediaminetetraacetic acid, and diethylenetriaminepentaacetic acid). The stability constants and thermodynamic parameters derived from these studies may provide some indication of covalency in heavy actinide-aliphatic amine complexation chemistry. The stability constants derived for all metal-ligand complexes in this study were compared to lanthanide stability constants of the same aminopolycarboxylates (APCs) in linear free energy relationships to address, in part, whether a difference in selectivity exists between the late actinides and their lanthanide counterparts. Californium and einsteinium displayed a 2% difference in selectivity from europium and gadolinium, respectively, in absolute terms. Little evidence was obtained that shows intra-actinide selectivity between the aliphatic amines and the trivalent actinides.
    • Advanced power theories and signal decomposition methods for controlling smart converters in smart grid applications

      Simões, M. Godoy; Harirchi, Farnaz; Al-Durra, Ahmed; Mohagheghi, Salman; Ammerman, Ravel F.; Steele, John P. H. (Colorado School of Mines. Arthur Lakes Library, 2017)
      During last two decades, the enormous level of aggregation of distributed generation units DGUs (widely known as the technology of Microgrids), in addition to increasing usage of nonlinear loads in power systems has raised new mathematical-conceptual challenges, specially in power electronics. Most of the traditional power theories and concepts therein, have been defined and formulated for simple balanced and linear systems. As a result, most of them are not directly applicable in case of new system structures with a considerable amount of uncertainty in the production and nonlinearity in the consumption. Due to uncertainties injected by the dynamic behavior of the DGUs (mostly renewable-based), the power components in the traditional power theories should be redefined under highly dynamic behavior of the power signals. Moreover, corresponding justifications need to be implemented to adapt all the related control strategies and compensation techniques. Renewable-based energies, such as wind and solar, are inherently uncertain power sources which can have unpredictable unwanted impacts on power flow, voltage regulation, and result in distribution losses. Microgrids that are quickly expanded through the power networks and power theories play a critical role in all the control strategies designed for these systems. When operating in the islanded mode, low-voltage Microgrids can exhibit considerable variation of amplitude and frequency of the voltage supplied to the loads, thus affecting power quality and network stability. Limited power capability in Microgrids can cause a voltage distortion which affects measurement accuracy, and possibly cause tripping of protections. Besides, the nonlinear and unbalanced loads obscure the traditional power definitions and equations. In such contexts, a reconsideration of power theories is required, since they form the basis for supply and load characterization and accountability. Moreover, developing new control techniques for harmonic and reactive compensators are mandatory, because they operate in a strongly interconnected environment and must perform cooperatively to face system dynamics, ensure power quality, and limit distribution losses. The main purpose of this research is to improve the quality, reliability and stability of future electrical power delivery by improving the overall performance of smart Microgrids through usage of advanced time-domain power theories (such as instantaneous power theory (PQ) and Conservative Power Theory (CPT)). Another major contribution of this work is the introduction of new mathematical power theory concepts (termed Enhanced Instantaneous Power Theory (EIPT)) in addition to implementation of adequate new control strategies. This work specially expanded based on a specific viewpoint which says that power theories can be interpreted as advanced signal decomposition techniques which are used as the initial step in electrical power signals analysis. This signal analysis step forms the fundamental headstock for power electronic interfaces controller design procedure. After describing the mathematical fundamentals of our modified power theory, EIPT; then this method is used as a time-domain signal decomposition approach for relevant applications. Exploiting the fine levels of information revealed through analysis of the power signals with the mentioned decomposition approaches, we provide more levels of freedom in the case of control frameworks. This research also investigate the interesting application of EIPT, besides other practical power theories such as CPT, in islanding detection problems, where a new instantaneous intelligent passive islanding detection strategy will be introduced. In a nutshell, developing new time-domain power theory concepts while exploiting the inherent capacities of the pre-existing power theories, the main goal of this work will be designing a reliable and smart multifunctional control scheme that can address all the aforementioned challenges.
    • Analysis of landslide volume, structures, and kinematics from satellite imagery of the 2016 Lamplugh rock avalanche, Glacier Bay National Park and Preserve, Alaska, An

      Zhou, Wendy; Bessette-Kirton, Erin K.; Santi, Paul M. (Paul Michael), 1964-; Coe, Jeffrey (Colorado School of Mines. Arthur Lakes Library, 2017)
      During the past five years occurrences of large rock avalanches over glaciated terrain in Glacier Bay National Park and Preserve (GBNP), Alaska have drawn attention to the complex, highly variable, yet poorly understood dynamics of these events. The objective of this research is to study the emplacement processes of the Lamplugh rock avalanche through an analysis of the volume and distribution of material in conjunction with structures and surficial features within the deposit. This research demonstrates the ability to use high-resolution remotely sensed data to study rock avalanches in glaciated terrain and provides an improved framework with which to estimate many of the uncertainties affecting volume measurements in glacial environments. The Lamplugh rock avalanche occurred on June 28, 2016 and is the largest rock avalanche on record in GBNP. WorldView satellite stereo imagery was used to derive pre- and post-event, high-resolution (2m) Digital Elevation Models (DEMs). Differenced DEMs were used to calculate both source and deposit volumes and examine variations in deposit thickness. DEMs were also used in conjunction with high-resolution (~0.5m) optical imagery to map landslide structures and surficial features. The characterization of landslide structures and the evaluation of volume and thickness were used to make interpretations about emplacement processes. Unmeasured ice changes between the acquisition of pre- and post-event imagery and the rock avalanche occurrence were found to underestimate the total volume of deposited material by 91%. A large amount of surficial material downslope of the source area, much of which was likely snow and ice, was scoured and entrained during emplacement. The rock avalanche deposit is also characterized by lateral and distal rims that are significantly thicker than the interior of the deposit. The examination of overall deposit geometry in addition to the identification of structures and surficial features within the deposit indicates that emplacement occurred as multiple surges of failed rock avalanche material. An improved understanding of rock avalanche processes is critical to future hazard assessments of rock avalanches travelling on ice within GBNP and in other glaciated regions.
    • Anticipation guided proactive intention prediction for assistive robots

      Zhang, Xiaoli; Burmeister, Joshua; Steele, John P. H.; Zhang, Hao (Colorado School of Mines. Arthur Lakes Library, 2017)
      When a person is performing a task, a human observer usually makes guesses about the person's intent by considering his/her own past experiences. Humans often do this when they are assisting another in completing a task. Making guesses not only involves solid evidence (observations), but also draws on anticipated evidence (intuition) to predict possible future intent. Benefits of guessing include, quick decision making, lower reliance on observations, intuitiveness, and naturalness. These benefits have inspired a proactive guess method that allows a robot to infer human intentions. These inferences are intended to be used by a robot to make predictions about the best way to assist humans. The proactive guess involves intention predictions which are guided by future-object anticipations. To collect anticipation knowledge for supporting a robot's intuition, a reinforcement learning algorithm is adopted to summarize general object usage relationships from human demonstrations. To simulate overall intention knowledge in practical human-centered situations to support observations, we adopt a multi-class support vector machine (SVM) model which integrates both solid and anticipated evidence. With experiments from five practical daily scenarios, the proactive guess method is able to reliably make proactive intention predictions with a high accuracy rate.
    • Application of the seismic quality factor versus offset and azimuth (QVOA) for fractured reservoir characterization

      Davis, Thomas L. (Thomas Leonard), 1947-; Avila Vizuett, Karla Cecilia; Trainor-Guitton, Whitney; Sarg, J. F. (J. Frederick); Ronquillo Jarillo, Gerardo (Colorado School of Mines. Arthur Lakes Library, 2017)
      Fracture characterization of a reservoir is very important because the presence of fractures determines the flow of hydrocarbons during production. Accurate modeling of the fracture network can help in optimizing the production of the reservoir. Fractures affect the amplitudes of the seismic waves, therefore, seismic attenuation is used to determine their characteristics. Here, I use a new technique called QVOA which involves the evaluation of the seismic attenuation and its variation with offset (O), and azimuth (A). Variation of seismic attenuation from QVOA methodologies can help in determining fracture characteristics where conventional methods fail. The QVOA method is a two step process where seismic attenuation is computed first and then its variation is determined with respect to offset and azimuth. I compute seismic attenuation using four different techniques based on the spectral ratio and frequency-shift methods. The variation with respect to offset and azimuth is determined using approximate method of sectors (ASM) and approximate truncate method (ATM). Orientation and the B-gradient of the fracture characteristics are obtained using this QVOA technique. I apply this QVOA technique to 3D seismic data acquired over the Gulf of Mexico region where the target is a naturally fractured carbonate reservoir. Fracture orientation in the reservoir region obtained using the QVOA technique are verified with well log data. Finally, a comparative analysis of different techniques of seismic attenuation computation is provided, where the frequency-shift methods perform better than the spectral ratio method, and are more stable in the presence of noise. Variation of the B-gradient versus the azimuth suggests the presence of attenuation anisotropy in this reservoir.
    • Applications of geostatistical seismic inversion to the Vaca Muerta, Neuquen Basin, Argentina

      Davis, Thomas L. (Thomas Leonard), 1947-; Johnson, James R.; Lynn, Walter; Sonnenberg, Stephen A.; Benson, Robert D. (Colorado School of Mines. Arthur Lakes Library, 2017)
      In the Neuquén Basin the Vaca Muerta is a world class source rock. The reservoir consists of a distal marine shale that transitions into a carbonate slope. The study area is 600 km2 with a diverse dataset including 3D narrow azimuth seismic, surface microseismic, and six wells. The primary goals of this research study are to understand the relationship between critical rock properties and geomechanical moduli, extract further value from the available data by increasing resolution, and to understand what drives hydraulic stimulation. Total organic content (TOC) is a major driver with unconventional reservoirs. The presence of high TOC makes an unconventional play viable and impacts the geomechanical properties. Understanding the relationship between TOC and geomechanical parameters is critical. Young’s modulus, bulk modulus, and shear modulus show a clear correlation with TOC, while Poisson’s ratio does not. Incorporating geostatistical inversion provides a route to increased resolution, a constant pursuit of geoscientists and engineers alike. Us- ing increased resolution, favorable zones for hydraulic stimulation can be more accurately targeted. Hydraulically induced fractures are shown to grow in homogenous zones and to dissipate energy in heterogeneous zones. Geostatistical inversion can help identify local areas of homogeneity contained within zones of greater heterogeneity in order to create complex fracture networks optimal for production. Further to this, geostatistical inversion provides a platform to understand the uncertainty of the datasets being utilized. Finally, these elements can be tied together by integrating microseismic data in order to understand what drives stimulation. Young’s modulus, bulk modulus, and shear modulus show a relationship with the number and magnitude of microseismic events. The integration of a variety of datasets, through a number of processes, have shown that understanding geomechanical properties, increasing resolution, and being aware of drivers to stimulation can help optimize completions within the Vaca Muerta.
    • Applications of high resolution topography in tectonic geomorphology

      Nissen, Edwin; Johnson, Kendra L.; Zhou, Wendy; Davis, Elizabeth Van Wie; Hayes, Gavin; Gold, Ryan; Sava, Paul C. (Colorado School of Mines. Arthur Lakes Library, 2017)
      In recent years, sub-meter scale topography data have become increasingly available, mostly from laser scanning methods and satellite stereophotogrammetry. These data have increased the extent to which we can remotely document and analyze tectonic features, and allow us to capture higher resolution details. In particular, we can use DEMs to carefully map surface deformation from ground-rupturing earthquakes---both at the fault and in the near-field---producing detailed records of rupture patterns, slip magnitude, damage zone properties, and scarp preservation; these characteristics can then be considered with dynamic rupture processes and the earthquake cycle. In this thesis, we approach tectonic questions with high resolution topography data, observing the geomorphic signatures of recent earthquakes, and developing routines that extract rupture information from modern surfaces. The three body chapters consist of independent journal manuscripts connected by this common theme. In Chapter 2, we demonstrate a low-cost and logistically practical procedure for independently creating high resolution (sub-decimeter) topography data, rather than relying on industrial methods. This method builds on photogrammetry to resolve surface shape from overlapping photographs and a few georeferencing points, producing sufficient quality elevation data to make geometric measurements. Recovered elevations are comparable to those from traditional laser scanning methods to within reported errors. We demonstrate our methodology at two tectonic sites in California: (1) a slip rate site, where fluvial features are offset by the southern San Andreas fault Banning strand; and (2) a section of the 1992 $M_w$~7.2 Landers earthquake scarp, which is undergoing continuous degradation monitoring. This method has become commonplace in tectonics, and among other geologic applications. In Chapter 3, we revisit the densely vegetated 1959 M$_w$~7.2 Hebgen Lake earthquake surface rupture with newly acquired lidar topography data. We produce dense throw distributions along the major faults activated by the earthquake, in most places observing offsets that greatly exceed 1959 measurements. This suggests that---although the scarps do not consistently express a distinct, muliti event topographic signal---we have captured at least one paleo-earthquake, in agreement with trenching results. We compute roughness along the throw distribution for each fault, finding a smoother distribution for a fault on steep talus slopes that exploits weak bedding planes, which we interpret to reflect slip from only the most recent earthquake. We treat the scarp as the source's planar intersection with the topography, from which we recover shallow fault dip. We resolve highly segmented structures over wavelengths of 100s of meters, and are unable to fit continuous scarps to a single plane. Segment dip averages range $\sim$30-45$^\circ$, much shallower than dips from seismology and geodesy, suggesting anti-listric source geometry that exploits inherited Laramide structures near the surface. Our results have cautionary implications when interpreting paleo-earthquake magnitude and source geometry from morphologically simple scarps. In Chapter 4, we use a pair of lidar datasets spanning the 2010 $M_w$~7.2 El~Mayor--Cucapah earthquake to reveal shallow fault geometry near the northern rupture extent. The earthquake accommadated NW-SE right-lateral shear along the Pacific-North American plate boundary, and also had a normal component. Models mostly agree on moderate to steeply dipping source fault geometry except where a road cut reveals that locally, the Paso Superior fault dips at $<$20$^\circ$. We use a 3D displacement field from Iterative Closest Point (ICP) lidar differencing to determine whether near-field deformation in the road cut proximity corresponds to a shallowly dipping structure. We compute fault dip using heave and throw ratio derived from displacement profiles projected onto the primary rupture. We fit planes to four continuous surface ruptures near the road cut. We model elastic dislocation, inverting surface deformation for simplified, homogenous planar sources. We consistently find moderate to steep dips at distance from the road cut, but shallow dips near or $<$20$^\circ$ for a $\sim$2~km fault length centered on the fault exposure. Our results suggest that the shallowly dipping Paso Superior fault did activate during the 2010 event, and postulates that other low-angle normal faults observed in the geologic record may activate during earthquakes. Taken together, these results show how high resolution topography can be used to understand the structures activated by modern earthquakes. Single, post-event datasets can be used to interpret historic or prehistoric ruptures, with the precaution that scarps may appear morphologically simple, while dataset pairs that capture near-fault surface displacement can provide additional constraints on shallow structures.
    • Assessment of the progression of coal mine subsidence in Colorado, using InSAR

      Zhou, Wendy; Puente Querejazu, Alvaro; Baker, Scott; Santi, Paul M. (Paul Michael), 1964- (Colorado School of Mines. Arthur Lakes Library, 2017)
      Coal mine subsidence is the deformation of the Earth’s surface caused by the collapse of rock and unconsolidated deposits into underground mine voids or entries, induced by the extraction of coal. This deformation can cause damage to roads, buildings, utility lines, or pipelines. Colorado’s history of coal mining dates back to the beginning of the 20th century and continues to this date. Inactive mines in Colorado pose a potential risk for 25,000 people along the front range urban corridor. An important step towards mitigating this problem, is to assess the applicability of remote sensing techniques for characterizing the vertical displacement, lateral extent, and formation sequence of subsidence features, in relation to the extent and timing of mining activities. This project evaluates the applicability of Interferometric Synthetic Aperture Radar (InSAR) for quantifying and delineating the progression of subsidence from active coal mines in Colorado. The data used for this analysis is limited to SAR images collected by the Advanced Land Observation Satellite (ALOS), the Environmental Satellite (ENVISAT) and the European Remote Sensing (ERS) satellites I and II. Three study areas were selected to assess the method’s applicability under different conditions (density of vegetation, topography, activity status, and mining method). The study areas are the Deserado Mine, the King Coal II Mine, and the historical mining complex in Colorado Springs. The pertaining imagery was archived in a database, organized by the relative orbit and frame of provenance. SAR images were processed with General Mapping Tools SAR (GMT5SAR) and the Generic InSAR Analysis Toolbox (GIAnT) to produce a time series of quantified deformation. The results were ultimately compared with the extent of mine workings and subsidence models to assess the accuracy of the results. Clear subsidence signatures were found over the Deserado Mine and the King Coal II mine. Deformation above the longwall mine (Deserado) was detected with all the utilized data sets, proving that InSAR can be used to delineate the extent of subsidence over such type of mines. Deformation above the active room and pillar mine (King Coal II) was only detected using ALOS data. No clear signs of deformation were found within the historical mining complex in Colorado Springs. The low density of coherent pixels limits the use of InSAR for delineating troughs above such mine type.
    • Behavior of palladium as a getter for lanthanide fission products in U-Mo-Ti-Zr fast reactor fuels, The

      Mishra, Brajendra; Olson, D. L. (David LeRoy); Howard, Cameron Tyler; Porter, Jason M.; Liu, Stephen; King, Jeffrey C.; Paglieri, Stephen N. (Colorado School of Mines. Arthur Lakes Library, 2017)
      One of the hurdles to extending the life of metallic fast reactor fuel alloys is Fuel-Clad Chemical Interaction (FCCI), a phenomenon which occurs between fuel and cladding resulting in thinning of the cladding. The cause of FCCI is the reaction between cladding constituents (e.g. iron and nickel) and lanthanide fission products generated in the fuel (e.g. lanthanum and cerium). This interaction can produce localized melting of the cladding, reducing its thickness over the life of the fuel element. It has been suggested that FCCI can be hindered by doping the fuel with palladium, a candidate getter for lanthanide fission products. There is therefore interest in demonstrating the efficacy of this particular lanthanide getter for realistic fast reactor fuel analogues. Work is presented based on the U-M (M=50Mo-43Ti-7Zr, wt. pct.) alloy system both with, and without, palladium additions. The research was conducted using depleted uranium alloys developed as metallurgical surrogates for real spent fuels. Burnup was simulated using cerium as a mock lanthanide fission product to assess the behavior of palladium with respect to fuel and cladding constituents. The behavior of palladium in terms of microstructural evolution was studied from both as-cast and annealed surrogate fuel specimens as well as diffusion couples between surrogate fuel alloys and type HT-9 stainless steel cladding. Results derived from characterization of these metallurgical surrogate experiments are presented and it is shown that palladium is a promising getter for lanthanide fission products in the given alloy system.
    • Benchmarking of neutron flux parameters at the USGS TRIGA reactor in Lakewood, Colorado

      Greife, Uwe; Alzaabi, Osama E.; Sarazin, Frederic; Shafer, Jenifer C.; Sellinger, Alan (Colorado School of Mines. Arthur Lakes Library, 2017)
      The USGS TRIGA Reactor (GSTR) located at the Denver Federal Center in Lakewood Colorado provides opportunities to Colorado School of Mines students to do experimental research in the field of neutron activation analysis. The scope of this thesis is to obtain precise knowledge of neutron flux parameters at the GSTR. The Colorado School of Mines Nuclear Physics group intends to develop several research projects at the GSTR, which requires the precise knowledge of neutron fluxes and energy distributions in several irradiation locations. The fuel burn-up of the new GSTR fuel configuration and the thermal neutron flux of the core were recalculated since the GSTR core configuration had been changed with the addition of two new fuel elements. Therefore, a MCNP software package was used to incorporate the burn up of reactor fuel and to determine the neutron flux at different irradiation locations and at flux monitoring bores. These simulation results were compared with neutron activation analysis results using activated diluted gold wires. A well calibrated and stable germanium detector setup as well as fourteen samplers were designed and built to achieve accuracy in the measurement of the neutron flux. Furthermore, the flux monitoring bores of the GSTR core were used for the first time to measure neutron flux experimentally and to compare to MCNP simulation. In addition, International Atomic Energy Agency (IAEA) standard materials were used along with USGS national standard materials in a previously well calibrated irradiation location to benchmark simulation, germanium detector calibration and sample measurements to international standards.
    • Biogeochemical and ecological impacts resulting from beetle-induced forest mortality

      Sharp, Jonathan O.; Dickenson, Eric R. V.; Brouillard, Brent; Hogue, Terri S.; Spear, John R.; Rodriguez, Derrick (Colorado School of Mines. Arthur Lakes Library, 2017)
      Over the last two decades, increasing temperatures and drought conditions have caused unprecedented bark beetle infestation across western North America. As forest die-off ensues, several aspects of the hydrologic cycle are altered due to canopy loss, altered evapotranspiration, and decreased water uptake by infested trees. Additionally, the cessation of root exudates along with the decay of enhanced litterfall following tree death alters biogeochemical cycling. These shifts may alter water quality or produce nutrient feedbacks into the atmosphere and hydrosphere. While modeling and field investigations have begun to elucidate these responses, questions still exist regarding whether a certain level of infestation is required to produce these secondary effects along with perceptions of increased fire risk that drive forest management policies. This work focuses on the ecological and biogeochemical shifts that occur following beetle infestation by investigating 1) shifts in aromatic carbon loading and subsequent disinfection byproduct (DBP) formation potential in beetle-impacted watersheds, 2) alterations in fire severity following mountain pine beetle infestation, and 3) how geochemical responses within soil horizons are influenced as a function of localized tree mortality severity. Analysis of quarterly municipal monitoring data from 2004-2014 from six municipalities in the Rocky Mountain region of Colorado containing varying levels of beetle infestation were analyzed. Watersheds containing >50% areal infestation were found to have significantly increasing total organic carbon and DBP concentrations, with increases continuing nearly one decade after initial infestation. Alarmingly, DBP concentration trends at high-impact sites were found to exceed regulatory maximum contaminant levels during the final two years of analysis (2013-2014). Focused surface water sampling at each municipality further revealed elevated carbon loading and aromaticity in beetle-impacted sites, increasing DBP formation potential particularly during precipitation events. This additional sampling supports the hypothesis that degrading tree material along with elevated groundwater tables may be impairing surface waters used for human consumption following extensive beetle infestation. The relationship between mountain pine beetle infestation and fire severity was analyzed from 2000-2014 across the Western United States. Maps delineating zones of beetle-impacted lodgepole and ponderosa pine forest were overlain with remote sensing fire severity data products providing validation across a range of ecoregions and fire conditions. Results demonstrate a decline in fire risk following beetle infestation with beetle-impacted forests burning 65-77% and 90-94% as severely compared to unimpacted controls; respectively, for lodgepole and ponderosa pine. Forest management decisions should be wary in removing beetle-impacted forests to mitigate fire threats as these actions may not reduce fire risk and can have unintended impacts to water quality. Finally, as the severity of beetle infestation within a forest may impact biogeochemical response, near surface horizons (litter, organic, and mineral soil) were sampled below live and beetle-killed lodgepole pine trees surrounded by varying extents of tree mortality to investigate potential compensatory effects from surviving trees. While some edaphic parameters were significantly different between green and grey phase trees (water content, pH, soil respiration) many biogeochemical signatures tracked with the extent of surrounding tree mortality (carbon aromaticity, C:N ratio, ammonium). Furthermore, the proportion of ammonium in the total nitrogen pool primarily increased once surrounding tree mortality exceeded 40%, demonstrating compensatory effects from surrounding live trees when infestation levels are minimal. Declining C:N ratios and an elevated proportion of ammonium indicate an enrichment of nitrogen in this N-limited ecosystem which may promote regrowth after forest disturbance.
    • Biohydrochemical enhancements for streamwater treatment: engineered hyporheic zones to increase hyporheic exchange, control residence times, and improve water quality

      McCray, John E.; Higgins, Christopher P.; Herzog, Skuyler Poage; Lucena, Juan C.; Singha, Kamini; Munakata Marr, Junko (Colorado School of Mines. Arthur Lakes Library, 2017)
      Nonpoint source pollution is the number one cause of water quality impairments to US rivers and lakes, and stormwater is the fastest growing category of nonpoint source pollution. In nature, nonpoint source pollutants can be treated by streambed sediments of impaired streams in a process analogous to biological sand filtration. This streambed biofilter is called the hyporheic zone (HZ), and it has been gaining attention in stream restoration due to its unique role in improving water quality. In particular, the HZ can attenuate pathogens (indicators), nutrients, and metals (the top three pollutant classes that lead to stormwater quality regulatory action) from the entire upstream watershed, thereby capturing nonpoint source pollution better than distributed BMPs. However, exchange between polluted surface waters and their HZs are often limited and inefficient. Prior to our project, the past two decades of research on the HZ had not been translated into effective Best Management Practices (BMPs) for stormwater managers. This knowledge gap prevented stormwater and stream restoration projects from properly engineering HZs to increase hyporheic exchange and optimize (nonpoint source) pollutant removal. In particular, an HZ BMP needs to 1) drive hyporheic exchange flows, 2) control hyporheic residence times, and 3) be customizable for removal of specific contaminants of concern. Currently, low-head dams are used to drive hyporheic exchange, but standard designs do not control residence times and are not customizable, so they have minimal water quality benefits. The objectives of this PhD research were to develop and test a novel engineered HZ BMP to improve streamwater quality. Specifically, we utilized manipulations of streambed media to create a modular BMP called Biohydrochemical Enhancements for Streamwater Treatment (BEST). BEST modules are comprised of subsurface modifications to streambed permeability to drive hyporheic exchange, paired with reactive geomedia (e.g., woodchips) to enhance biogeochemical conditions needed for pollutant removal. BEST were explored through three studies. The first featured a numerical model evaluating multiple BEST modular designs on hyporheic exchange flows and contaminant attenuation. The most promising BEST design from the numerical model was then installed in a constructed stream flume alongside an all-sand control channel. The second study featured conservative and reactive tracer experiments to compare the impact of BEST on hyporheic transient storage and attenuation of a model compound, resazurin, which undergoes first-order microbially mediated degradation under aerobic conditions. The third study used the same flumes to compare BEST to the control for the attenuation of urban stormwater contaminants: nitrogen and atrazine. The cumulative results of these studies indicate that BEST can provide substantial improvements to streamwater quality over reaches of hundreds of meters in small streams or constructed urban stormwater channels (e.g., flow rates < 10 L/s). Numerical models highlight the importance of impermeable “book ends” in BEST modules to maximize hyporheic exchange and control residence times. Flume studies of this design showed that BEST increased the effective HZ exchange volume by 50% compared to the control, which led to 45-95% increases in the reach-scale attenuation rates of multiple stormwater contaminants. In other words, stormwater channels that incorporate BEST modules could reach water quality targets in 45-95% less reach length compared to an all-sand streambed (e.g., sand filter). The BEST design tested in these experiments was well suited to fast, aerobic reactions (e.g., nitrification), but future designs will be tailored for anaerobic reactions to broaden the range of pollutants that can be treated (e.g., nitrogen via denitrification). Overall, the results suggest that BEST could be an adaptable and complementary stormwater and stream restoration BMP to increase attenuation of nonpoint source pollutants within small, impaired streams.
    • Biophysical mechanisms regulating Von Willebrand disease, arterial thrombosis, and deep vein thrombosis in microfluidic models of vascular injury

      Neeves, Keith B.; Lehmann, Marcus; Spear, John R.; Krebs, Melissa D.; Marr, David W. M. (Colorado School of Mines. Arthur Lakes Library, 2017)
      Thrombus formation is regulated by biophysical mechanisms in ways that are not fully understood. Platelets are transported to injuries at rates that depend not only on the bulk flow, but also collisions with red blood cells (RBC). Their ability to tether to the subendothelium depends on shear stresses at the injury and can be impaired by deficiencies in Von Willebrand factor (VWF). The subsequent rate of fibrin formation is a function of the mass transfer of coagulation factors and of surface reaction rates. In this thesis, I detail studies of these biophysical mechanisms using microfluidic models of arterial thrombosis and a novel venous thrombosis model. In a flow chamber, I perfused whole blood from patients presenting with clinical bleeding over collagen. I found that at elevated shear rates, platelet accumulation was sensitive to VWF deficiencies in patients with low VWF levels and type I Von Willebrand Disease (VWD). From the assay, I was able to discriminate type I VWD patients from healthy controls, suggesting that microfluidic technologies can be adapted into a clinical setting. Using a low Reynolds number microfluidic mixer I developed, I showed that a clinically relevant increase in hematocrit increased platelet accumulation but not fibrin formation on a fibrillar collagen surface at an arterial shear rate. In concert with in vivo and in silico data, this result suggests that an elevated hematocrit increases the contact time platelets have with a growing thrombus, leading to more bond formations and an accelerated thrombus growth. This result provides a rationale for antiplatelet therapy for patients exhibited elevated hematocrit. Venous thrombosis is less characterized than arterial thrombosis. To my knowledge, I created the first microfluidic system that includes secondary flows and coagulation as a way to model the propagation of a venous thrombus out of a valve pocket. While traditionally thought of as a coagulation dependent system, my model shows the critical importance of platelets and platelet-RBC collisions in this propagation. This study justifies antiplatelet therapy for deep vein thrombosis, and provides a novel framework for future mechanistic studies of platelet activation and function in venous thrombosis.
    • Central Laser Facility at the Pierre Auger Observatory. Studies of the atmospheric vertical aerosol optical depth and other applications to cosmic ray measurements, The

      Wiencke, Lawrence; Medina Hernandez, Carlos Francisco; Sarazin, Frederic; Squier, Jeff A.; Dreyer, Christopher B.; Wakin, Michael B. (Colorado School of Mines. Arthur Lakes Library, 2017)
      The two largest observatories in the world dedicated to the study of Ultra High Energy Cosmic Rays (UHECR) are the Pierre Auger Observatory (Auger) in Mendoza, Argentina and the Telescope Array (TA) in Utah, USA. The measurements of the cosmic ray flux by Auger and TA present a discrepancy at the highest part of the energy spectrum. In this thesis, I study if this discrepancy can be attributed to instrumental effects related to the measurements of the atmospheric aerosol contents in Auger. The Auger Fluorescence Detector (FD) measures the scattered light from laser tracks generated by the Central Laser Facility (CLF) and the eXtreme Laser Facility (XLF) located near the center of Auger, to estimate the vertical aerosol optical depth (τ (z,t)). A good knowledge of τ (z,t) is needed to obtain unbiased and reliable FD measurements of the energy of the UHECR primary particle. The CLF was upgraded substantially in 2013 to improve laser reliability. A substantial part of my Ph.D work is dedicated to building, maintaining and analyzing data from this upgraded facility. The upgraded CLF includes a backscatter Raman LIDAR which independently measures τ (z,t). For the first time in a cosmic ray experiment, two years of measurements of τ (z,t) obtained with the Raman LIDAR are compared with the measurements obtained with the FD. Based on these comparisons, an alternative atmospheric database was created to study its effects on the measurements of the flux as a function of energy. The resulting energy spectrum plot is found to be more compatible with the energy spectrum plot released by TA.
    • CFD modeling of a tailgate ventilation condition in a longwall bleeder system

      Brune, Jürgen F.; Juganda, Aditya; Bogin, Gregory E.; Grubb, John W. (Colorado School of Mines. Arthur Lakes Library, 2017)
      Face ignitions at the longwall are a serious hazard in underground coal operations and can lead to a major mine explosion. Despite having methane monitoring systems mounted on the shearer and at various locations on the longwall face, undetected methane accumulations can still occur and result in face ignitions. With the use of Computational Fluid Dynamics (CFD), the interaction between the air flow at the longwall face and factors that contribute to accumulations around the face can be modeled and visualized in great detail. The results confirm that the tailgate corner of the longwall face is a critical area prone to face ignitions and thus needs to be properly monitored. Roof falls at the tailgate entry inby the face and/or poor caving conditions behind the shields can both pose a safety risk at any longwall operation. Poor gob caving can lead to insufficient face air quantity with which to dilute methane at the tailgate corner, while a blocking of the tailgate by a roof fall can carry methane-contaminated air from behind the shields back into the face near the tailgate corner and pull the explosive gas zones (EGZs) inside the gob and closer to the face. Additional monitoring locations are deemed necessary to provide early indicators for such events.
    • Characterization of ferroelasticity in rare-earth orthophosphates by nanoindentation

      Packard, Corinne E.; Wilkinson, Taylor M.; Reimanis, Ivar E. (Ivar Edmund); Diercks, David R.; Stebner, Aaron P. (Colorado School of Mines. Arthur Lakes Library, 2017)
      Superelasticity, or the rubber-like effect, describes the phenomenon of a material being able to ‘recover’ after an external strain, beyond the elastic limit, is removed. This behavior has been exhibited by shape memory alloys, as well as the emerging materials field of shape memory ceramics, and may be caused by the material undergoing deformation mechanisms such as phase transformation or twinning/detwinning – also known as ferroelasticity. Superelastic materials are known to be attractive candidates for shape memory materials as well as applications with actuating, sensing, and damping needs. Rare-earth orthophosphates are a group of ceramics that are known to exhibit incredible flexibility with lanthanide element substitution as well as high resistance to chemical and thermal degradation. These materials have also been shown to undergo both of the deformation mechanisms associated with superelasticity. Nanoindentation is a promising technique for studying superelasticity due to its ability to run large-scale experimental matrices and the fact that the technique is highly sensitive and therefore able to pick up even the smallest amounts of recovery. Pioneer indentation testing of several rare-earth orthophosphates near the monazite/xenotime boundary has shown indentation recovery as a slope change that occurs during the unloading portion of test. Similar behavior has been attributed to phase transformations in silicon and twinning in germanium. This thesis conducts an in-depth study to determine the conditions under which these anomalous indentation features occur. Indentation recovery was not restricted to the phase transforming xenotimes, but could also occur in the non-phase transforming monazites as well; thus it was concluded that the presence of an elbow in the indentation data was not a unique identifier of phase transformation in rare-earth orthophosphates. Furthermore, it was shown that the elastic modulus of each of these compositions approached the value predicted by simulations and hardness was consistently above 5 GPa, provided that the samples were processed to nearly full density. Multiple indentations completed on a polycrystalline specimen of monazite GdPO4 revealed frequent anomalous unloading behavior with a large degree of recovery; therefore, an excised indentation was analyzed to determine the cause of recovery using TEM. The presence of a twin along the (100) orientation, along with a series of stacking faults contained within the deformation site, provide evidence that the mechanism of recovery in GdPO4 is twinning-based ferroelasticity. In addition to the large instances of superelasticity, cyclic loading of single-crystal monazite-structured GdPO4 was shown to exhibit recovery ratios similar to that of the shape memory alloy NiTi at 0.9, and exceeded the amount of achievable dissipated energy (250 MJ/m3 for GdPO4 vs. 10-20 MJ/m3 for NiTi). Furthermore, this study provides the first evidence that twinning-based ferroelasticity may be used to achieve superelasticity in ceramics, making REPO4s potentially attractive candidates for actuation and damping applications.
    • Characterization of magnetically driven colloidal microwheels and their fibrinolytic applications

      Marr, David W. M.; Neeves, Keith B.; Disharoon, Dante; Wu, Ning; Leiderman, Karin (Colorado School of Mines. Arthur Lakes Library, 2017)
      Colloids carrying payloads of medication have become a popular drug delivery approach. Since it is not always possible to rely on blood circulation to distribute the colloids to the target site in the body, researchers seek to develop methods of controlling colloid movement. We advance the development of a magnetic system that moves colloids using a canted rotating magnetic field. Beads containing superparamagnetic iron oxide crystals assemble into wheel-like structures that rotate in alignment with the field and roll via wet friction along adjacent surfaces. These micro-wheels (μwheels) are suitable for drug delivery. We utilize μwheels to deliver tissue plasminogen activator (tPA) to a blood clot. tPA can be used to treat stroke but is rarely used because it can cause hemorrhaging. We show that μwheels functionalized with tPA combine mechanical and biochemical mechanisms to achieve enhanced fibrinolysis over that of soluble tPA at therapeutic concentrations. μwheels conjugated with an effective tPA concentration of 3.6 μg/mL degrade fibrin twofold faster than soluble tPA at 10 μg/mL. μwheels are an effective fibrinolytic because of their ability to target, penetrate into and concentrate at a clot. Here, we show that μwheels powered by a magnetic field are capable of exiting a laminar flow field and entering a connecting blocked channel. These experiments suggest that the μwheel translational mechanism is robust enough to navigate vasculature in order to target occlusions. Finally, we use total internal reflection microscopy (TIRM) to characterize the mechanism of μwheel translation. A sphere translating against a glass slide under influence of the magnetic field is 89 ± 39 nm from the slide. The gap distance can be affected by changing the load force on the μwheel or electrochemical interactions between the μwheel and surface, suggesting that μwheel interactions with vasculature will be tunable. The μwheels used herein are a novel and exciting drug delivery system whose potential applications are not limited to treating stroke.