• 3D seismic image processing for interpretation

      Hale, Dave, 1955-; Wu, Xinming; Sava, Paul C.; Davis, Thomas L. (Thomas Leonard), 1947-; Bialecki, Bernard; Tang, Gongguo (Colorado School of Mines. Arthur Lakes Library, 2016)
      Extracting fault, unconformity, and horizon surfaces from a seismic image is useful for interpretation of geologic structures and stratigraphic features. Although interpretation of these surfaces has been automated to some extent by others, significant manual effort is still required for extracting each type of these geologic surfaces. I propose methods to automatically extract all the fault, unconformity, and horizon surfaces from a 3D seismic image. To a large degree, these methods just involve image processing or array processing which is achieved by efficiently solving partial differential equations. For fault interpretation, I propose a linked data structure, which is simpler than triangle or quad meshes, to represent a fault surface. In this simple data structure, each sample of a fault corresponds to exactly one image sample. Using this linked data structure, I extract complete and intersecting fault surfaces without holes from 3D seismic images. I use the same structure in subsequent processing to estimate fault slip vectors. I further propose two methods, using precomputed fault surfaces and slips, to undo faulting in seismic images by simultaneously moving fault blocks and faults themselves. For unconformity interpretation, I first propose a new method to compute a unconformity likelihood image that highlights both the termination areas and the corresponding parallel unconformities and correlative conformities. I then extract unconformity surfaces from the likelihood image and use these surfaces as constraints to more accurately estimate seismic normal vectors that are discontinuous near the unconformities. Finally, I use the estimated normal vectors and use the unconformities as constraints to compute a flattened image, in which seismic reflectors are all flat and vertical gaps correspond to the unconformities. Horizon extraction is straightforward after computing a map of image flattening; we can first extract horizontal slices in the flattened space and then map these slices back to the original space to obtain the curved seismic horizon surfaces. The fault and unconformity processing methods above facilitate automatic flattening and horizon extraction by providing an unfaulted image with continuous reflectors across faults and unconformities as constraints for an automatic flattening method. However, human interaction is still desirable for flattening and horizon extraction because of limitations in seismic imaging and computing systems, but the interaction can be enhanced. Instead of picking or tracking horizons one at a time, I propose a method to compute a volume of horizons that honor interpreted constraints, specified as sets of control points in a seismic image. I incorporate the control points with simple constraint preconditioners in the conjugate gradient method used to compute horizons.
    • Activation of CdTe solar cells using molecular chlorine

      Wolden, Colin Andrew; Trevithick, Jason R.; Ohno, Timothy R.; Agarwal, Sumit (Colorado School of Mines. Arthur Lakes Library, 2016)
      Cadmium telluride-based photovoltaics are presently the leading commercialized thin film solar cell technology. A critical step during device fabrication is exposure of the as-deposited CdTe absorber to CdCl2 vapor at ~400 ºC for 10 – 30 min. This step is critical for obtaining high power conversion efficiencies and has been correlated with recrystallization and grain growth, passivation of grain boundaries, and heterojunction interdiffusion. This activation step is difficult to control and capex intensive. In addition, the use of CdCl2 presents a significant environmental concern due to its high solubility in water. In this thesis we explored molecular chlorine (Cl2) as an alternative to CdCl2 for activation of CdTe solar cells. This activation treatment could potentially serve as a direct replacement for CdCl2 processing in commercial module manufacturing. Molecular Cl2 diluted in N2/O2 mixtures was exposed to as-deposited FTO/CdS/CdTe stacks in a custom-built quartz tube furnace, enabling independent control of Cl2/Ar flowrate (1 – 5 sccm), temperature (375 – 420 ºC), oxygen concentration (0 – 25 %), and treatment time (0 – 10 min). The (111) texture coefficient was tracked during experiments to measure extents of recrystallization as parameters were explored, followed by correlations with device performance. Within the parameters explored it was found that a threshold temperature of T ≥ 400 ºC was required for recrystallization of the films. This coincides with the typical optimum temperature used for CdCl2 activation. In stark contrast to CdCl2 activation, very short treatment times (~1 min) and no oxygen ambient were needed for optimal device performance. In addition, the Cl2 process delivered significantly improved uniformity and run to run reproducibility relative to conventional CdCl2 activation. The Cl2 process also displayed a much larger process window with respect to temperature and eliminated delamination. A final optimization of 1.5 sccm of 3% Cl2/Ar, T = 415 ºC, 800 sccm N2, and 2 min resulted in an 11.6% efficient device with an open circuit voltage > 800 mV. This value surpasses the best reports in the literature (9-10 %) and exceeds that of many alternative activation agents (HCl, NaCl, etc.). Best device performance was less than the 14.5% baseline efficiency achieved with standard CdCl2 treatment. Device characterization revealed losses in both Voc (~50 mV) and Jsc (2-3 mA/cm2). Quantum efficiency showed that collection in the bulk CdTe region was 10% lower than standard CdCl2 activation, suggesting defect-based bulk recombination. Transmission electron microscopy and elemental mapping revealed that grain coalescence was incomplete under Cl2 activation, leaving regions with voids or low density. Both chlorine and oxygen accumulate at these defects, explaining the substandard performance. The optimal chlorine exposure was the lowest that could be reliably delivered, and it is recommended that further studies reduce the Cl2 concentration by an order of magnitude or more. In addition, longer times may be required to improve grain coalescence and extend interdiffusion at the heterojunction. The source of oxygen impurities is unclear and requires further investigation. Nevertheless these initial studies are quite promising and a pathway is provided to further improve Cl2 activation and enable its use as a cost-effective alternative to conventional CdCl2.
    • Adolescent sleep and the circadian pacemaker

      Diniz Behn, Cecilia; Stack, Nora; Pankavich, Stephen; Leiderman, Karin (Colorado School of Mines. Arthur Lakes Library, 2016)
      Adolescence is a critical time of social, physical, and mental development. Adolescents often exhibit a circadian phase delay in which they tend to go to bed later and wake up later compared to adults. This thesis seeks to understand the adolescent phase delay and its relationship to the circadian pacemaker, the body’s master clock. Using a dynamic circadian pacemaker model, we identify parameters that affect features of the circadian system that may contribute to the phase delay. Specifically, we focus on the effect of light on the phase and amplitude of the circadian pacemaker as model parameters are varied. We compare simulation results with data characterizing the adolescent clock under different weekend sleep protocols. This work has implications for understanding the mechanisms associated with the adolescent phase delay and may inform efforts to create schedules for adolescents that mitigate sleep loss and the resulting impacts on physical and cognitive performance.
    • Advanced beneficiation of bastnaesite ore through centrifugal concentration and froth flotation

      Anderson, Corby G.; Schriner, Doug; Taylor, Patrick R.; Spiller, D. Erik (Colorado School of Mines. Arthur Lakes Library, 2016)
      Gravity separation and flotation studies have been conducted on Molycorp bastnaesite ore in order to determine if new beneficiation schemes present a more selective and more economical alternative than that which is currently employed at Mountain Pass. Literature on bastnaesite, monazite, barite, and calcite flotation and gravity concentration principles was surveyed. Flotation reagent additions were determined using components that have shown preferential floatability of bastnaesite and monazite over the gangue minerals. Hallimond Tube microflotation tests were performed on crushed and ground ore samples. Heavy liquid separation with sodium polytungstate was used to investigate the effectiveness of gravity separation on the ore. Shaking table and Falcon concentrator tests were performed to gravity concentrate the ore. A gravity-concentrated feed was floated and compared with a non-concentrated ore feed to illustrate the benefit of preconcentration. An economic analysis was generated for flotation plants operating with and without gravity preconcentration that would sell products with two distinct grades and recoveries. Qualitative microflotation tests produced little selective separation of the rare earth minerals (bastnaesite, parisite, and monazite) from the gangue (calcite, barite, dolomite, and quartz). Heavy liquid tests illustrated the sink/float behavior of the minerals at different specific gravities of separation. Their results suggest that at higher specific gravities the calcite floats while the bastnaesite and barite sink. Shaking table tests showed potential to effect such a separation, but optimum conditions were not determined. A Falcon centrifugal concentrator was used to carry out tests according to a Design of Experiments matrix generated with Stat Ease Design Expert 9. The best conditions from those trials were determined, and the tests were repeated to verify the desirability of those parameters. Bench flotation was then used to compare the standard feed at plant conditions to a feed consisting of the blended gravity concentrates. The flotation results showed that the preconcentrated feed outperformed the typical plant feed. Economic analysis of a plant with and without gravity preconcentration shows that gravity preconcentration, although more capital-intensive, will yield a higher annual profit and a better 10-year net present value.
    • Advanced microgrid design and analysis for forward operating bases

      Sen, Pankaj K.; Reasoner, Jonathan; Ammerman, Ravel F.; Kroposki, Benjamin David, 1968- (Colorado School of Mines. Arthur Lakes Library, 2016)
      This thesis takes a holistic approach in creating an improved electric power generation system for a forward operating base (FOB) in the future through the design of an isolated microgrid. After an extensive literature search, this thesis found a need for drastic improvement of the FOB power system. A thorough design process analyzed FOB demand, researched demand side management improvements, evaluated various generation sources and energy storage options, and performed a HOMER® discrete optimization to determine the best microgrid design. Further sensitivity analysis was performed to see how changing parameters would affect the outcome. Lastly, this research also looks at some of the challenges which are associated with incorporating a design which relies heavily on inverter-based generation sources, and gives possible solutions to help make a renewable energy powered microgrid a reality. While this thesis uses a FOB as the case study, the process and discussion can be adapted to aide in the design of an off-grid small-scale power grid which utilizes high-penetration levels of renewable energy.
    • Advancing internal erosion monitoring using seismic methods in field and laboratory studies

      Mooney, Michael A.; Parekh, Minal L.; Prasad, Manika; Griffiths, D. V.; Wayllace, Alexandra; Woodson, Sandra; Snorteland, Nathan (Colorado School of Mines. Arthur Lakes Library, 2016)
      This dissertation presents research involving laboratory and field investigation of passive and active methods for monitoring and assessing earthen embankment infrastructure such as dams and levees. Internal erosion occurs as soil particles in an earthen structure migrate to an exit point under seepage forces. This process is a primary failure mode for dams and levees. Current dam and levee monitoring practices are not able to identify early stages of internal erosion, and often the result is loss of structure utility and costly repairs. This research contributes to innovations for detection and monitoring by studying internal erosion and monitoring through field experiments, laboratory experiments, and social and political framing The field research in this dissertation included two studies (2009 and 2012) of a full-scale earthen embankment at the IJkdijk in the Netherlands. In both of these tests, internal erosion occurred as evidenced by seepage followed by sand traces and boils, and in 2009, eventual failure. With the benefit of arrays of closely spaced piezometers, pore pressure trends indicated internal erosion near the initiation time. Temporally and spatially dense pore water pressure measurements detected two pore water pressure transitions characteristic to the development of internal erosion, even in piezometers located away from the backward erosion activity. At the first transition, the backward erosion caused anomalous pressure decrease in piezometers, even under constant or increasing upstream water level. At the second transition, measurements stabilized as backward erosion extended further upstream of the piezometers, as shown in the 2009 test. The transitions provide an indication of the temporal development and the spatial extent of backward erosion. The 2012 IJkdijk test also included passive acoustic emissions (AE) monitoring. This study analyzed AE activity over the course of the 7-day test using a grid of geophones installed on the embankment surface. Analysis of root mean squared amplitude and AE threshold counts indicated activity focused at the toe in locations matching the sand boils. This analysis also compared the various detection methods employed at the 2012 test to discuss a timeline of detection related to observable behaviors of the structure. The second area of research included designing and fabricating an instrumented laboratory apparatus for investigating active seismic wave propagation through soil samples. This dissertation includes a description of the rigid wall permeameter, instrumentation, control, and acquisitions systems along with descriptions of the custom-fabricated seismic sensors. A series of experiments (saturated sand, saturated sand with a known static anomaly placed near the center of the sample, and saturated sand with a diminishing anomaly near the center of the sample) indicated that shear wave velocity changes reflected changes in the state of stress of the soil. The mean effective stress was influenced by the applied vertical axial load, the frictional interaction between the soil and permeameter wall, and the degree of preloading. The frictional resistance was sizeable at the sidewall of the permeameter and decreased the mean effective stress with depth. This study also included flow tests to monitor changes in shear wave velocities as the internal erosion process started and developed. Shear wave velocity decreased at voids or lower density zones in the sample and increased as arching redistributes loads, though the two conditions compete. Finally, the social and political contexts surrounding nondestructive inspection were considered. An analogous approach utilized by the aerospace industry was introduced: a case study comparing the path toward adopting nondestructive tools as standard practices in monitoring aircraft safety. Additional lessons for dam and levee safety management were discussed from a Science, Technology, Engineering, and Policy (STEP) perspective.
    • Advancing understanding of the relationship between soil conditioning and earth pressure balance tunnel boring machine chamber and shield annulus behavior

      Mooney, Michael A.; Nelson, Priscilla P.; Mori, Lisa; Hedayat, Ahmadreza; Brune, Jürgen F.; Kaunda, Rennie; Alavi, Ehsan (Colorado School of Mines. Arthur Lakes Library, 2016)
      Earth pressure balance tunnel boring machines (EPB TBMs) are used for the excavation of tunnels in soft ground beneath the water table to minimize surface settlements by counteracting earth and water pressures. To guarantee effective EPB TBM face support and performance, it is necessary to understand the mechanical behavior of foam-conditioned soil under realistic pressure conditions. This dissertation investigates the behavior of foam-conditioned soil under applied total pressures. The effect of total stress, effective stress, and key soil parameter void ratio on the shear strength and compressibility of foam-conditioned soil is examined. The test results show that the vane shear strength and compressibility are mainly influenced by the void ratio and effective stress, which starts to develop below a certain e/emax ratio. Further tests were performed to determine if muck collected from the belt conveyor of an EPB TBM can be used to assess the behavior of conditioned soil in the excavation chamber. The study found little to no relationship between the measured muck shear strength and TBM torque. It was concluded that the collected muck is not a representative sample of the conditioned soil in the chamber. This was attributed to the deterioration of foam over time, and the extended time the soil is transported and mixed in the screw conveyor. In addition, this thesis investigates if apparent density can be used to assess the soil conditioning performance and the soil behavior in the excavation chamber of an EPB TBM. It was found that apparent density evaluation methods can be used to identify air pockets and plugging issues in the excavation chamber of an EPB. Furthermore, the study investigates if conditioned soil from the face fills and pressurizes the gap between the EPB shield exterior and the surrounding ground. The study showed that the pressures in the shield gap mainly follow the bulkhead pressure, which indicates that conditioned soil from the face fills and pressurizes the shield gap. It was found that the shield pressures are mainly influenced by the soil type, soil conditioning, bulkhead pressure, and the grouting pressure.
    • Aggregation in organic light emitting diodes

      Zimmerman, Jeramy D.; Meyer, Abigail; Sellinger, Alan; Furtak, Thomas E. (Thomas Elton), 1949- (Colorado School of Mines. Arthur Lakes Library, 2016)
      Organic light emitting diode (OLED) technology has great potential for becoming a solid state lighting source. However, there are inefficiencies in OLED devices that need to be understood. Since these inefficiencies occur on a nanometer scale there is a need for structural data on this length scale in three dimensions which has been unattainable until now. Local Electron Atom Probe (LEAP), a specific implementation of Atom Probe Tomography (APT), is used in this work to acquire morphology data in three dimensions on a nanometer scale with much better chemical resolution than is previously seen. Before analyzing LEAP data, simulations were used to investigate how detector efficiency, sample size and cluster size affect data analysis which is done using radial distribution functions (RDFs). Data is reconstructed using the LEAP software which provides mass and position data. Two samples were then analyzed, 3% DCM2 in C60 and 2% DCM2 in Alq3. Analysis of both samples indicated little to no clustering was present in this system.
    • Alternating direction implicit finite difference methods for the heat equation on general domains in two and three dimensions

      Bialecki, Bernard; Wray, Steven; Nicholas, Michael; Strong, Scott A. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Alternating direction implicit methods are a class of finite difference methods for solving parabolic PDEs in two and three dimensions. The convergence properties of these methods on rectangular domains are well-understood. We wish to extend this approach to solve the heat equation on arbitrary domains. We begin by dropping a perturbation term for the boundary conditions of the Peaceman-Rachford method in the Dirichlet problem on a two-dimensional box. We show theoretically that this modified method converges with order two under the discrete maximum norm. This is confirmed by numerical tests that show the modified method converges with order two under both the discrete maximum norm and the discrete L2 norm. In three dimensions, similar modifications allow us to extend the Douglas method. On an arbitrary domain, the extended method converges with order two under the discrete L2 norm but with order one under the discrete maximum norm.
    • Anaerobic baffled reactor pilot: bridging the gap to energy positive wastewater treatment

      Figueroa, Linda A.; Hahn, Martha J.; Figueroa, Linda A.; Munakata Marr, Junko; Cath, Tzahi Y.; Posewitz, Matthew C. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Domestic wastewater contains chemical energy that is wasted by aerobic biological treatment processes, which require energy and maximize solids production. Mainstream anaerobic treatment of domestic wastewater has the potential be to the sustainable treatment scheme of the future because of the energy generation potential, lower energy requirements and reduced solids generation. A concern with direct anaerobic treatment of raw municipal wastewater in temperate climates is the effect of the low water temperatures on the organic removal rates and process stability. Anaerobic baffled reactors (ABRs) have a simple design, decouple hydraulic and solid retention time and provide excellent retention of solids in response to load variations. The ABR configuration allows for a naturally occurring spatial separation of the microorganisms that perform the sequential steps of hydrolysis, acidogenesis, and methanogenesis, in the conversion of complex organics to methane. Long-term performance of psychrophilic ABR systems for raw wastewater is lacking and it is critical to develop the data needed for technology adoption by wastewater utilities. A four-cell ABR was operated for two years treating raw domestic wastewater at ambient water and air temperatures down to 12 ˚C and -10 ˚C, respectively. The 1000-liter pilot reactor operated at a 12-hour hydraulic residence time and was located in the Headworks building of the Plum Creek Water Reclamation Authority, Castle Rock, Colorado. The two-year pilot study was conducted to determine the treatment efficiency of suspended solids and organic matter removal and methane production. To improve understanding of microbial dynamics for model development and potential diagnostic tools, the relative abundances of bacteria, archaea and methanogens were measured in each of the ABR cells and the relationship to conventional performance parameters was examined. The total suspended solid and organic removals were approximately 80% and 50%, respectively; methane production was stoichiometric and no settled solids were wasted over two-years. The full 12 hours of hydraulic residence time was required to achieve stoichiometric methane production from the organic matter removed. The estimated energy content of the biogas produced per unit volume of wastewater treated averaged 0.45 kWh/m3 and no energy input was required. Acetoclastic species were the dominant methanogens in the latter two cells, which also had the highest methane production and acetate utilization. The anaerobic baffled reactor was able to biologically achieve enhanced primary treatment of raw municipal wastewater under winter conditions with methane production. Anaerobic primary treatment may be incorporated at the front end of an existing facility to reduce organic loading to downstream processes, reduce aeration demand, reduce biomass production, and increase energy generation. The implementation of anaerobic primary treatment in conjunction with anaerobic secondary treatment will significantly reduce solids production and maximize methane production from the wastewater organics and has the potential to be energy positive.
    • Analogy matching with function, flow and performance

      Turner, Cameron J.; Morgenthaler, Peter R.; Van Bossuyt, Douglas L.; Dean, Jered (Colorado School of Mines. Arthur Lakes Library, 2016)
      Multiple methods exist to achieve design innovations. Analogical reasoning is one such method that has been shown be effective. The Design Analogy Performance Parameter System (DAPPS) project presented here is developing a method to aid in analogy generation by specifying a set of critical functions and desired design performance improvements. DAPPS uses performance parameter metrics to compare user inputs to potential analogical sources, thus stimulating analogical reasoning and innovative designs. We showcase the validation aspect of the DAPPS project. Proof-of-concept has previously been performed and implemented via the Design Repository & Analogy Computation via Unit-Language Analysis (DRACULA) framework. The steps for validation of DRACULA have been divided into two parts: 1) generation of numerical metrics with which multiple analogical generation methods may be compared and 2) case study assessments which will compare between various these methods. Previous works have shown that within a design problem there are functions that are the most important to meet the product requirements or customer needs. These functions have been defined as critical functions. In many products, there are multiple critical functions that create a critical chain. These critical chains are the primary focus of the comparison of the various analogical generation methods. Critical chains have both functional groupings and architecture. The functional groupings of the chains are the functions contained within the chain while the architecture is the order of the components. Within the architecture, five different ways to relate two architectures have been identified, including: identical, mirrored, disordered, mirror disordered, and unique. By comparing the function chains of analogical sources to design problems in both the functional groupings and the five architectural relations, we show a correlation in design characteristics such as innovativeness, ability to be implemented, similarity, and applicability of analogical sources. The correlation of design characteristics is the primary focus of research. If this new method of measuring the relationships between function chains proves effective, then it can be applied to DRACULA and DAPPS to validate the method as well as guide research towards the improvement of the DRACULA analogy matching algorithms.
    • Analysis of stress and geomechanical properties in the Niobrara Formation of Wattenberg field, Colorado, USA

      Davis, Thomas L. (Thomas Leonard), 1947-; Grazulis, Alexandra K.; Tutuncu, Azra; Andrews-Hanna, Jeffrey C. (Colorado School of Mines. Arthur Lakes Library, 2016)
      In Wattenberg Field the Niobrara Formation is the primary productive zone for horizontal drilling and completions. It is an unconventional reservoir made up of alternating chalk and marl layers which require hydraulic fracturing for completion. The main study area for this project is a four square mile region where time-lapse multicomponent seismic surveys have been acquired. This area includes the Wishbone section, where 11 horizontal wells have been drilled, and is the focus of dynamic reservoir characterization. The primary goal of this research study is to investigate relationships between geomechanics, stress and fractures. Determining the geomechanical properties of the reservoir is essential for better reservoir management. Geology is the main driver controlling production, due to the presence of fault compartmentalization in the field. The central graben, within the Wishbone section, causes geologic heterogeneity and displays signs of high net pressure. This is due to a larger increase in pore pressure, ultimately decreasing effective stress. Outside of the graben, naturally fractured areas, displaying decreasing net pressure trends, will maximize fracture network surface area during completions. This allows for a larger volume of rock to be stimulated, and a greater chance of opening pre-existing fractures. As far as re-fracturing efforts are concerned, areas outside of the graben which are brittle and have low stress anisotropy should be targeted to create complex fracture networks. Geomechanical and stress information about the reservoir is vital for predicting fracture propagation. After investigation of fracture characterization trends, we have a better understanding of stimulated areas within the Wishbone section. Specific completion techniques can be applied to stages based on geomechanical properties and geologic location. Fracture networks defined through the integrated dynamic reservoir characterization process provide targets for future re-fracturing efforts.
    • Analytical solution for anomalous diffusion in fractured nano-porous reservoirs

      Ozkan, E.; Albinali, Ali; Dahl, Carol A. (Carol Ann), 1947-; Tutuncu, Azra; Ozbay, M. Ugur; Yin, Xiaolong (Colorado School of Mines. Arthur Lakes Library, 2016)
      This dissertation presents an analytical fluid flow model for multi-fractured horizontal wells in unconventional naturally fractured reservoirs. The solution builds on anomalous diffusion concept and fractional calculus to account for non-uniform velocity in highly disordered porous media. The mathematical model is derived for an isothermal, single phase and slightly compressible fluid. The model computes the transient bottomhole pressure solution for the well and is referred to as Tri-Linear Anomalous Diffusion and Dual-Porosity (TADDP) model. In this work, a time-dependent flux incorporating the fractional derivative of the process variable is utilized and combined with the classical mass balance equation. The temporal derivative power is used to describe the heterogeneity of the flow field. Fractional calculus allows accounting for non-localities of flow and the heterogeneity caused by the contrast between the properties of the rock matrix and natural fractures. The anomalous diffusion formulation is applied to the tri-linear model (TLM) by Ozkan et al. (2009) where the dual-porosity idealization is utilized to describe the naturally fractured reservoir between hydraulic fractures (the so-called stimulated reservoir volume, SRV) and fluid transfer takes place i) from tight rock matrix to natural fractures, ii) from natural fractures to the hydraulic fractures and iii) from hydraulic fractures to the wellbore. The option to use the conventional Darcy’s law for the flux is also available. Flow is treated independently in the rock matrix and natural fractures. In these domains, transport can be modeled by anomalous diffusion or normal diffusion. This approach provides flexibility in modeling natural fractures of discrete or sparse nature as well as modeling complex flow field in the matrix due to the presence of organic and inorganic content. Results show that the solution concurs with the established models and adheres to the general physics of fluid flow. The effects of anomalous diffusion at different reservoir regions can be interpreted from pressure data and delays in the flow can be addressed by adjusting the diffusion exponent. The model offers a range of answers compared to the conventional dual-porosity models and provides utility to model various flow heterogeneities and reservoir types.
    • Analyzing the potential for unstable mine failures with the calculation of released energy in numerical models

      Ozbay, M. Ugur; Poeck, Eric C.; Griffiths, D. V.; Brune, Jürgen F.; Nakagawa, Masami (Colorado School of Mines. Arthur Lakes Library, 2016)
      Unstable failure in underground mining occurs when a volume of material is loaded beyond its strength and displaces suddenly. It is recognized on various scales, from small rock bursts to the collapse of pillars or entire sections of a mine. The energy that is released during smaller scale events is manifested through the ejection of material, which can pose a hazard to the safety of miners. Larger scale events generate seismic waves as mine workings are damaged and may entrap miners or terminate production. This dissertation focuses on the analysis of unstable failure in an underground room and pillar mining environment. The potential for violent pillar failure is assessed using numerical modeling techniques and a parametric approach to loading conditions and material strength properties. The magnitude of instability is quantified by calculating the release of kinetic energy that occurs as failure progresses in each simulation. Fundamental mechanisms associated with the release of kinetic energy are analyzed in a series of finite difference models, and the results are compared with analytical solutions to illustrate the applicability of the energy calculations to increasingly complex modes of failure. Back analyses are performed on two room and pillar mine collapse events from the western United States by constructing large-scale models and reproducing widespread failure. The values of energy released in two-dimensional models are extrapolated by assuming a depth of failure in the third direction, and the total energy values are compared to the documented seismic magnitudes from each collapse through empirical equations. With further development of this numerical modeling approach, energy consideration may be used to study the potential for instability in a wide variety of mining excavations and identify the associated range of hazards.
    • Anti-corrosion behaviour of barrier, electrochemical and self-healing fillers in polymer coatings for carbon steel in a saline environment

      Mishra, Brajendra; Usman, Chaudhry Ali; Spear, John R.; Cornejo, Ivan; Liu, Stephen; Olson, D. L. (David LeRoy) (Colorado School of Mines. Arthur Lakes Library, 2016)
      Coatings serve many purposes on metallic surfaces, including tribological coating, anti-static coating, electromagnetic shielding coating, anti-reflective coating, and anti-corrosion. Polymer coatings for corrosion protection of metallic substrates are mostly related to long-term performance needs. In addition to the barrier effect, thecoating must have the ability to inhibit the corrosion process if the protective barrier is disrupted. Incorporating fillers, such as metallic oxides, layered fillers and conducting polymer, improves long termed anti-corrosion along with barrier, mechanical, electrical and optical, rheological, and adhesion properties, and resistance to the environmental degradation. The mechanism of protection of incorporated fillers can be divided into different types: barrier, electrochemical, and self-healing. Further, the anticorrosive paints, containing lead or hexavalent chromium as active pigments, represent a risk to human health and theenvironment. Furthermore, restrictionsimposed by national and international agencies on the use of classical red lead, lead chromate, and zinc chromate, have led towards the development of non-toxic organic and inorganic anticorrosion pigments incorporated in thepolymer. In this thesis,three anti-corrosion fillers were investigated for the protection of carbon steel:(1) Graphene as abarrier filler, (2) Nickel Zinc Ferrites as electrochemical filler, (3) and Poly(ortho-anisidine) doped with heteropolyanions as the self-healing filler. Poly(vinyl butyral) (PVB)/graphene coatings showed improved barrier protection and short-term electrochemical properties for carbon steel. The PVB/graphene nanocomposite coating exhibited lower long-term electrochemical protection due to water uptake. On the other hand, functionalized graphene/PVB coatings improved both electrochemical and barrier properties. Large increase in pore resistance of the functionalized graphene/PVB coatings indicated lower water penetration through the coatings. Furthermore, Polyaniline-functionalized graphene (PA-G)/PVB coatings showed better protection for carbon steel for very long times, compared to unmodified graphene/PVB and functionalized graphene/PVB coatings. The long-term electrochemical properties of ferrites were studied both in solution, and polymer coatings. In solution, the corrosion inhibition was inversely proportional to increasing concentration of cations in ferrites (Zn and Ni). The increased corrosion was attributed to the galvanic corrosion of steel due to the adsorption of metallic cations from the ferrites. In polymer composite coating, increased corrosion protection was observed with increasing ferrite concentration up to 1 wt. percent of ferrites. A mechanism of corrosion protection of steel with ferrites in polymer coatings was demonstrated. The metallic cations traveled to the surface of the polymer coating, forming a protection layer which stopped further corrosion of the substrate. The self-healing coatings were developed by doping poly (o-anisidine) (PoA) with hetero-atoms such as Tungsten silicic acid (TSA), and phosphomolybdic acid (PMA). The doped PoA were further incorporated in PVB to manufacture a composite coating for steel protection. The doped-PoA /PVB coatingexhibited increased positive open circuit potential after 45 hours of immersion compared to that of neat PVB coating. The open circuit profile of doped-PoA /PVB coating further indicated the self-healing mechanism corresponding against the corrosion process.
    • Application of 3D reconstruction by stereo vision for the purpose of assessing weld quality, The

      Steele, John P. H.; Neill, Andrew M.; Moore, Kevin L., 1960-; Van Bossuyt, Douglas L.; Hoff, William A.; Payares-Asprino, Maria C. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Welding is one of the most integral and fundamental technologies enhancing the quality and safety of our lives today. Applications range from mining to construction to automotive manufacturing, to aerospace, and most are being pushed toward higher quality standards as well as toward the adaptation of automated welding systems. Safety, cost, performance, and reliability are driving the need for faster, higher performance systems in the welding industry. There is an increasing demand for better quality monitoring and process control, especially in automated welding systems where the sensing ability and adaptive skill of an experienced human welder are no longer in the loop. Several technologies exist to monitor welding process waveforms, weld joint geometry, and provide post-process weld inspection but one of the most important goals for modern welding systems is quality monitoring and process control to achieve the desired geometry and weld quality while the weld is being made, that is, online. This would more information available to an automated welding system, enable real-time quality monitoring, and facilitate the development of adaptive closed-loop control of the welding process. Weld sensing technologies available today do not provide measurements of the three dimensional geometry during the welding process sufficient to support these capabilities. This thesis describes the development of a stereo vision system capable of providing near real-time scaled three dimensional reconstruction of a portion of the weld pool and the surface of the deposited weld bead. A pair of cameras have been mounted on a welding robot in an eye-in-hand configuration. The cameras have been calibrated to high precision and used to collect sequences of images from the welding process. These images were then rectified for stereo matching, filtered, and passed through four stereo correspondence algorithms to evaluate the algorithms for efficacy and feasibility. The results from the stereo correspondence were then used to construct a three-dimensional model of the weld bead features to a resolution of approximately 1 millimeter. The results presented in this thesis provide scaled weld pool reconstruction with a level of speed and detail that improve on the capability of current technology and establish a baseline for further development of automated welding systems. Analysis of errors, speed of calculation, and limitations of the process are included. Recommendations for future investigations based on the findings of this research are also provided.
    • Application of the Lagrangian particle-tracking method to simulating mixing-limited, field-scale biodegradation

      Benson, David A.; Ding, Dong; Maxwell, Reed M.; Sharp, Jonathan O.; Munakata Marr, Junko (Colorado School of Mines. Arthur Lakes Library, 2016)
      Measured (or fitted) reaction rates at field-scale sites are commonly observed significantly lower than batch-scale rates. The reduced rates are usually attributed to poor mixing of reactants. In this study, the Lagrangian particle tracking and reaction (PTR) method is used to characterize the effect of mixing for different types of reactions at a range of scales (from laboratory columns to field-scale tests). In the PTR method, the reactants are represented by particles. The particle/particle reactions are determined by a combination of two probabilities: 1) the physics of transport and 2) the energetics of reaction. The first is a direct physical representation of the degree of mixing in an advancing interface between dissimilar waters, and as such lacks empirical parameters except for the user-defined number of particles, which can be determined from concentration autocovariance. First, the PTR method is used to simulate two column experiments of bimolecular reaction and transport. When compared to the solution of the advection-dispersion-reaction equation (ADRE), the experiments and the PTR simulations showed on the order of 20\% to 40\% less overall product, which is attributed to poor mixing. The poor mixing also leads to higher product concentrations on the edges of the mixing zones. Second, the PTR method is extended to biodegradation, which is commonly characterized by Michaelis-Menten (Monod) (M-M) chemical kinetics. The PTR method not only matches the M-M equation under ideal conditions, but also captures the characteristics of non-ideal conditions such as imperfect mixing, disequilibrium, and limited availability of biologically active sites. These features are shown using hypothetical systems and are also successfully applied to a column study of carbon tetrachloride (CT) biodegradation. Finally, the extended PTR method is used to simulate a field bioremediation project at the Schoolcraft, Michigan site. The remediation was conducted by injecting a denitrifying bacterium, along with sufficient substrate, into the aquifer to degrade a plume of CT. Comparisons between simulated results and field measurements indicate that, unlike previous applications of the ADRE, the PTR method is able to match the field-scale experiment using the rate coefficients from batch experiments.
    • Application of time-lapse seismic shear wave inversion to characterize the stimulated rock volume in the Niobrara and Codell reservoirs, Wattenberg field, CO

      Davis, Thomas L. (Thomas Leonard), 1947-; Mueller, Staci K.; Trudgill, Bruce, 1964-; Sava, Paul C. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Advances in horizontal drilling and completions in shale reservoirs have allowed operators to extract hydrocarbons within low permeability reservoirs that were once impossible to access. The integration of time-lapse multicomponent seismic data with engineering technology aids in the characterization of these reservoirs through monitoring. This thesis investigates the fast and slow shear wave components of a time-lapse, nine-component seismic survey to determine the stimulated volume in the Niobrara and Codell reservoir intervals. The time-lapse post-stack inversions of the shear wave datasets provide insight into how the shear impedance is affected by hydraulic fracturing through the work of cross-equalized seismic shear impedances and shear wave splitting. The study area is the Wishbone Section within Wattenberg Field, CO, which is owned and operated by Anadarko Petroleum Corporation and contains eleven horizontal wells that vary in spacing and completion methods. Shear seismic data sets were acquired over this section before and after hydraulic stimulation. The time-lapse shear seismic inversions show an increase in fast shear wave velocity and a decrease in slow shear velocity after stimulation. The sensitivity of both the fast and slow shear seismic to stimulation correlates with the net pressure trends at each stage. Borehole image log interpretations are compared to the inversions to analyze the affect that a complex fracture network has on induced anisotropy. The stimulated volume for the Niobrara and Codell reservoir intervals are now more accurately defined. Time-lapse shear seismic is the only technology that is able to define the stimulated rock volume and reveal areas that are not being accessed by the wells currently drilled. These areas are now detected within the Wishbone section, and may be candidates for future re-completion.
    • Assessing middle-school teachers' attitudes and usage of CS Unplugged

      Camp, Tracy; Rader, Cyndi A. (Cyndi Ann); Kennicutt, Stephen D.; Painter-Wakefield, Christopher; Hudson, Derrick (Colorado School of Mines. Arthur Lakes Library, 2016)
      Computer Science (CS) Unplugged is a set of activities that allow students to explore computer science concepts without using a computer. Prior research on the effectiveness of CS Unplugged classroom activities has focused primarily on student attitudes and learning outcomes. Teacher understanding and comfort level with the curriculum must also be considered when assessing whether CS Unplugged is a viable option in the classroom. We developed a set of lesson plans that fit a traditional middle school classroom and presented these lessons to teachers through a 2-day workshop. We used surveys and deployment reports to determine whether teachers would be comfortable with the CS Unplugged activities, whether they understood the underlying material, and whether they would use CS Unplugged in their classrooms. Through our research, it was found that teachers are comfortable with the Unplugged curriculum, have high levels of understanding of the material, and will use the Unplugged activities in their classrooms.
    • Assessing the efficacy of BMPs to reduce metal loads in the Los Angeles River Basin at the watershed scale

      Hogue, Terri S.; Edgley, Ryan; McCray, John E.; Bellona, Christopher (Colorado School of Mines. Arthur Lakes Library, 2016)
      The Los Angeles River Basin is a large (825 mi2) and diverse watershed containing highly developed urban areas, as well as expansive chaparral landscapes. Municipalities within this watershed, and around the country, are required to meet water quality standards for pollutant loads in their receiving waterbodies. The current research quantifies the ability of BMPs to improve water quality in the Los Angeles River Basin as well as ancillary benefits (e.g. groundwater recharge) at the watershed scale. The EPA-developed System for Urban Stormwater Treatment and Analysis INtegration (SUSTAIN) model is used to simulate flow, load, and five BMPs. Two regional BMPs are modeled (infiltration trenches & dry ponds) and three distributed BMPs (vegetated swales, bioretention cells, porous pavement). Each BMP type provides a unique optimal benefit, infiltration trenches: infiltration rates, vegetated swales: water quality performance, dry ponds: lowest cost, porous pavement: minimal footprint (i.e. replaces existing infrastructure). The modeled BMPs are combined in various ways to produce six unique Compliance Options. Each Compliance Option equally satisfies water quality criteria, but consist of a unique composition of BMP types and quantity, therefore each Option offers a distinct blend of ancillary benefits and associated costs. Of the six compliance options crafted, none are optimal across all criteria, indicating stakeholders need to consider their particular near-term and long-term needs, and balance them with the various cost and ancillary benefits each Compliance Option can offer. The Compliance Option identified from the perspective of this research as meeting the region’s most pressing needs (reducing metal load, high stormwater infiltration & low cost of construction) contains a mix of vegetated swales and infiltration trenches (Option 3a). Option 3a significantly reduces peak flow (58%), infiltrates stormwater (172,000 AFY), and with the lowest construction cost ($3.8 billion) of all options considered. Although this research informs policymakers and stakeholders about the capacity of these six Compliance Options to provide a range of ancillary benefits, there remains tremendous opportunity to further develop the capability of BMPs and their understanding. More research is needed to spatially optimize the best locations for BMPs in a watershed, better quantify the infiltration of stormwater to recharge groundwater aquifers, as well as how to further improve the functionality of BMPs (e.g. optimizing geomedia or vegetation for particular pollutants or climates). Lastly there is a need for further data integration and monitoring to better inform the current state of water quality throughout watersheds and track its progress as BMPs are implemented.