Recent Submissions

  • Optimization techniques in coal markets: a global cost minimization and a multi-stage procurement strategy

    Turner, Cameron J.; Newman, Alexandra M.; Arigoni, Ashley; Dagdelen, Kadri; Hering, Amanda S.; Morton, David; Billups, Stephen (Colorado School of Mines. Arthur Lakes Library, 2016)
    Thermal coal is a prominent resource from which electricity is produced. In recent years, the price of this widely used commodity has declined, largely due to increases in environmental regulations, incentives for renewable resources, and technological advances in the production of natural gas, which is a cleaner-burning alternative fuel. As such, coal markets have drastically changed. We develop optimization models to help understand the current climate on a global scale and to help a domestic utility reevaluate its forward purchase strategy given depressed coal prices. We first develop a global thermal coal optimization model that minimize the cost to ship coal from countries that are net exporters to those that are net importers, taking into account coal quality specifications and shipping constraints, such as port and vessel capacity. Using this model, we explore the global effects of price variability, changes in operation from large market players such as China and India, and the impact of the Panama Canal expansion. We next develop a methodology for determining an optimal purchase strategy for a U.S. utility; using historical observations, we build a regression model to forecast prices, then select representative scenarios to include in a multi-stage stochastic program that minimizes the expected value and conditional value-at-risk (CVaR) of coal procurement. We formulate a time-consistent nested CVaR minimization model, compare its performance to an expected CVaR model, and show that the expected CVaR model may be better suited to minimizing risk in a multi-stage setting. We conduct out-of-sample testing to assess our solution performance under new price realizations. Finally, we apply an expected CVaR model to determine a utility's procurement strategy and recommend a purchase plan for implementation that is expected to save the company $151 million over a five-year horizon.
  • Relating nanoscale chemistry to electrical properties for high-efficiency Cu(In,Ga)Se2 solar cells

    Gorman, Brian P.; Stokes, Adam; Al-Jassim, Mowafak; Diercks, David R.; Toberer, Eric (Colorado School of Mines. Arthur Lakes Library, 2016)
    Cu(In,Ga)Se2 solar cells demonstrate better efficiencies than poly-crystalline Si and all other thin films technologies. Yet most of the gains in efficiency have been empirical and further fundamental understanding is necessary for continued improvement. This thesis will use advanced characterization techniques to show the unique self-compensating behavior along with alkali impurity incorporation as key reasons for the technology’s advancement. Atom probe tomography and scanning transmission electron microscopy are utilized to relate nanoscale chemistry to band structure. High point-defect densities (VCu, InCu, NaCu, KCu) (~1021 cm-3) are shown to lead to variable stoichiometry. Comparable defect densities in traditional semiconductors such as Si and GaAs would be deleterious. However, for Cu(In,Ga)Se2 this is not the case. Point-defects at grain boundaries and the p-n junction are related to pronounced downward shifts in the valence band maximum (~100 meV) and conduction band minimum (~30 meV) as well as n-type doping; which is ultimately predicted to be instrumental in the reduction of recombination and largely responsible for increased electrical performance.
  • Predicting parcel scale redevelopment within the Berkeley neighborhood in Denver, Colorado using linear and logistic regression

    McCray, John E.; Cherry, Lisa; Hogue, Terri S.; Eisenstein, William (Colorado School of Mines. Arthur Lakes Library, 2016)
    Many water resource issues associated with urban development result from increased impervious cover. As impervious cover increases, rainwater infiltration decreases leading to increased flows and potentially higher pollutant loads in the runoff. Most of the prior research on this topic investigates the increase of impervious cover through the transformation of undeveloped to developed regions, or the expansion of dense urban development into outlying suburban areas. A topic that is not as widely understood is the impact of infill redevelopment on stormwater runoff. Infill redevelopment is rapidly occurring in many Denver neighborhoods, where previously developed properties with low-density structures are being replaced by larger, higher density units. Regardless of impervious cover increase, these redevelopment projects are only required to incorporate stormwater detention and treatment systems if they are greater than one acre. Due to most of the redevelopment in Denver (86%) occurring on sites less than one acre, the burden of stormwater treatment and detention ultimately falls on the city. This study focuses on modeling the spatial distribution of infill re-development on a parcel scale to investigate its cumulative impacts on stormwater quality and quantity for near-term and future conditions. Future redevelopment and imperviousness is determined by distributing a “business as usual” linear growth scenario to the parcels with the greatest probability of future redevelopment. Then, a logistic regression model is used to determine the parcels that will be redeveloped. Results indicate that building cover change within study site from 2004 – 2014 followed a linear pattern. During this period the total building cover increased by 17% or 1.7 % per year on average. The logistic regression model determined the total value, year built, percent difference between current and max building cover, the current use classification: rowhomes, and current use classification apartments to be the greatest predictors of redevelopment, resulting in a model that was 81 % accurate. The "Building to Land Area Ratio" variable was found to be highly correlated with the “Improvement to Land Value Ratio”. However, the “Building to Land Area Ratio” was found to be a better predictor of redevelopment. The final model estimated an increase of 820,498 sq. ft. (18.8 acres) in building coverage between 2014 and 2024. This method will provide municipalities with a tool that can be used to estimate parcel scale impervious cover growth from publicly available planning data resulting in more informed urban watershed planning and policy development.
  • Structurally controlled Cu-Zn-(Co-Pb) mineralization in the Neoproterozoic Ombombo subgroup, Kaokoland, Namibia

    Hitzman, Murray Walter; Kuiper, Yvette; Allen, Nicole K.; Sarg, J. F. (J. Frederick); Ellmies, Rainer (Colorado School of Mines. Arthur Lakes Library, 2016)
    The Dolomite Ore Formation (DOF) is a Cu-Zn-(Co-Pb) horizon within the Neoproterozoic Ombombo Subgroup of the Kaoko Belt in northern Namibia. The horizon was mapped and sampled along its approximately 30-kilometer strike length in order to determine lateral facies variations in the DOF horizon, and the rocks immediately above and below this horizon. The goal was to constrain mechanisms of mineralization for this regionally geochemically anomalous unit, and to compare and contrast the DOF horizon with other sediment-hosted copper occurrences in the Otavi Mountainland of northern Namibia, in order to test whether the DOF horizon might be a viable exploration target. The DOF dips about 60⁰ to the north, averages <1m to 6m in thickness, and thickens towards the east. The horizon is an organic-rich (1.2-1.8% TOC), shaley, ankeritic dolostone that overlies interbedded dolostones and recessive siltstones (both with <1% TOC) in the east and interbedded arkose sandstones and recessive siltstones in the west. It contains pyrite with minor chalcopyrite, sphalerite, and galena with trace catterite. Supergene alteration resulted in formation of chalcocite and late-stage, sometimes zinc-enriched carbonate minerals. Although not obvious in outcrop, two drill holes through the DOF indicate that sulfides occur primarily within crack-and-seal quartz veins that likely formed during the Damaran Orogeny (560-550 Ma). The veins display little to no alteration other than weak silicified halos. Pyrite and pyrite ± chalcopyrite have sulfur isotopic values of -4 to +9‰ suggesting thermochemical reduction of sulfate probably derived from Neoproterozoic marine sulfate. Analysis of kerogen in the DOF suggests the rocks are overmature and given the Cu-Zn-Pb sulfide assemblage it is likely that the hydrothermal fluids had temperatures between 200 and 300⁰C. The DOF occurs at a deeper stratigraphic level than the base metal deposits of the Otavi Mountainland to the southeast, and it is likely that the DOF represents a deep expression of the types of mineralizing systems that produced these deposits. Results of this study suggests that carbonaceous strata in the Ombombo Subgroup that are cut by late Damaran-aged faults could have the potential for concentrating base metal sulfide or oxide minerals.
  • Chemical EOR process visualization using NOA81 micromodels

    Yin, Xiaolong; Kenzhekhanov, Shaken; Kazemi, Hossein; Hazim, Abbas; Neeves, Keith B. (Colorado School of Mines. Arthur Lakes Library, 2016)
    The main goal for all enhanced oil recovery (EOR) processes is to gain additional oil recovery after, or in some cases along primary and secondary recovery methods. For EOR processes that use immiscible displacement to increase oil recovery, the overall displacement efficiency can be increased by improving the mobility ratio or by increasing the capillary number. Core flooding is the traditional method to study the parameters above. However, microfluidic micromodels are causing huge interest from industry. In this study, we developed procedures to fabricate microfluidic porous media micromodels using a novel polymer – Norland Optical Adhesive 81 (NOA81). NOA81 helped to overcome limitations of previous work by Xu et al. (2014) such as crude oil incompatibility and deformation with higher temperatures. NOA81 micromodels were used to investigate visually the effects of temperature and different wettability on displacement efficiency in water and surfactant flooding. In addition, the natural fractures were introduced in porous media to study water and surfactant flooding in fractured reservoirs. The temperature effect on displacement efficiency demonstrated that increasing the temperature and decreasing interfacial tension (IFT) between fluids results in higher recovery factor and can be well correlated with the capillary number. The presence of connected natural fractures showed no recovery from matrix porous media in water flooding. However, in surfactant flooding 80% oil recovery was achieved due to lowering IFT. The wettability effect demonstrated that the water-wet micromodel produced 15% less than intermediate and oil-wet micromodels in water flooding due to early breakthrough. Meanwhile, surfactant flooding achieved almost equal high recovery in both water-wet and oil-wet surfaces. It was found that after breakthrough takes place, no notable oil recovery obtained in all water flooding experiments. In contrast, surfactant flooding recovered more with more pore volume injected. Oil recovery in both water and surfactant flooding was lower in water-wet fluid displacement. There are many other interesting phenomena observed during displacement efficiency experiments such as dead-end pore displacement, microemulsion generation and complexity of fluid flow dynamics in porous media.
  • Development of LTTW consumables for the enhancement of mechanical properties and residual stress management in thin steel welded joints

    Liu, Stephen; Yu, Zhenzhen; Wang, Zhifen; Packard, Corinne E.; Madeni, Juan Carlos (Colorado School of Mines. Arthur Lakes Library, 2016)
    For automotive industry, distortion introduced by welding of the thin sheet metals could be problematic in the assembly of auto-body. In addition, fatigue life of the lap-joint panels using advanced high strength steels (AHSS) is typically limited by the weldments. Low transformation temperature welding (LTTW) consumables are characterized by low martensite start temperature and large fraction of martensite forming in the weld. It can efficiently reduce the tensile residual stress because the volume expansion associated with the martensitic transformation compensates for the thermal contraction during cooling. In this work, a LTTW wire, EH200B, was designed for arc welding of DP980 AHSS thin plates. Its composition was tailored for electrode weldability optimization. Effects of the LTTW wire on weld microstructure, distortion, residual stresses distribution, and fatigue properties of the lap joint panels were studied in this research, and compared to the conventional ER70S-3 wire. In comparison to the weld microstructure of complete ferrite using conventional wire, the weldment using LTTW wire consists of 90 vol.% martensite. Distortion pattern of thin sheets with bead-on-plate (BOP) welds using LTTW wire was opposite from those using conventional wire. Residual stresses in the BOP welded sheets using the two types of wires were measured using neutron diffraction method. The mapping results along middle thickness of the plates showed that in longitudinal direction, which typically yields a higher stress level than other directions, LTTW wire welded sheet showed lower residual stresses in the weld and HAZ. Fatigue life of lap joint panels using LTTW wire was almost twice of that using conventional wire.
  • 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.
  • 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.
  • Syn-rift drainages and sedimentary fill architecture: a case study in the Jurassic of the Dampier Sub-basin

    Wood, Lesli J.; Schwarz, Stephen; Trudgill, Bruce, 1964-; Jobe, Zane R. (Colorado School of Mines. Arthur Lakes Library, 2016)
    Ancient rift basins host important hydrocarbon-bearing systems worldwide. A review of these systems indicates that the syn-rift reservoirs are commonly clastic, fluvio-deltaic facies with marine-related seals. Although the passive margin systems overlaying many of these basins have been well-studied and exploited, exploration into the deeper rift strata is riskier and relys on seismic surveys with little well or core data. Modern analogues, like the East African Rift System, provide insights into the early stages of rift development, but seismic analysis of ancient rifts is needed to analyze an entire rift cycle. Seismic surveys of the Jurassic sediments of the Dampier Sub-basin image the complete rift stratigraphy and contain well data through most of the syn-rift sediments. The purpose of this study is to better characterize the location and interaction of the reservoir and seal facies within the Dampier Sub-basin using seismic geomorphological techniques. This study focused on the regional play intervals (RPI) within the syn-rift of the Dampier Sub-basin: the J20 RPI, J30 RPI, J40 RPI, and the J50 RPI. The J20 RPI contained an axially prograding delta system, the J30 RPI contained a transverse prograding, coarse-grained delta system, the J40 contained deepwater fans and debrite deposits, and the J50 RPI contained a mix of delta and submarine fan systems. The interpreted syn-rift stratigraphy of the Dampier Sub-basin shows a switch from axial deposition during rift initiation to transverse deposition during rift climax. This change in dominant sediment drainage direction during rift evolution is important for exploration into syn-rift plays, especially since targeting high quality reservoir sands can be a challenge in these systems. Though transverse systems may contain immature sediments, this study shows that they can be significantly sized features and, when sealed in source rock quality shales, potentially productive plays.
  • Global sensitivity analysis for a collisionless plasma using a particle-in-cell method, A

    Pankavich, Stephen; Sattelberg, Ben; Constantine, Paul G.; Bialecki, Bernard (Colorado School of Mines. Arthur Lakes Library, 2016)
    Knowing the effects of physical parameters underlying the behavior of plasmas is useful when designing or investigating associated high velocity systems. We use a kinetic model given by the Vlasov-Poisson equations to consider global linear and gradient-based active subspace models that calculate sensitivity metrics related to the phenomena of Landau damping and the two-stream instability. Since analytic results are difficult or impossible to obtain for this system, we use a particle-in-cell method to numerically compute quantities of interest for which the sensitivity metrics can be calculated. In particular, we consider three equilibrium distributions that include Maxwellian and Lorentzian velocity distributions to demonstrate the usefulness of this method in understanding and quantifying parameter effects.
  • Map-based approaches for investigating sleep/wake dynamics

    Diniz Behn, Cecilia; Kalmbach, Kelsey R.; Leiderman, Karin; Pankavich, Stephen (Colorado School of Mines. Arthur Lakes Library, 2016)
    A homeostatic need for sleep increases with time awake and decreases during sleep. When the build up and recovery of sleepiness occurs sufficiently quickly, a person experiences two sleep cycles, a nap as well as nighttime sleep, each day. To investigate the transition between one and two sleep cycles per day, we consider the bifurcations of a previously developed model for human sleep/wake dynamics. As the time constants related to the build up and recovery of sleepiness are decreased, the system exhibits an incremental increase in the number of sleep cycles per day. Using a one-dimensional map to represent the dynamics of the system, we relate this map to a normal form for a piecewise continuous system which undergoes a border collision bifurcation, and provide numerical evidence for period-adding behavior. This analysis has implications for understanding the dynamics of the transition from napping to non-napping behavior in early childhood.
  • Design and simulation of reversible solid oxide cell systems for distributed scale energy storage

    Braun, Robert J.; Reznicek, Evan P.; DeCaluwe, Steven C.; Kee, R. J. (Colorado School of Mines. Arthur Lakes Library, 2016)
    Reversible solid oxide cells (ReSOCs) are an energy conversion technology that can be used to either produce power from fuel when electricity is needed (fuel cell mode), or produce fuel from electricity when excess energy is available (electrolysis mode). By leveraging C-O-H reaction chemistry and operating at intermediate temperatures, these cells can be mildly exothermic in both operating modes, eliminating the need for external heat input or high over-potential operation during electrolysis. Tanked storage of fuel (hydrogen, carbon monoxide, methane) and exhaust (water, carbon dioxide) allows ReSOC systems to provide stand-alone electrical energy storage services. However, tanks are inherently dynamic, and balance-of-plant hardware such as heat exchangers and compressors must be selected to operate efficiently in both modes. This work assesses the effects of tank dynamics and hardware off-design behavior on system design, performance, and cost for a 100 kW/800 kWh ReSOC system operating with a 16-hour round-trip cycle, suitable for distributed energy applications. A novel floating piston storage tank that allows near-constant storage pressure and reduced overall tank volume is proposed and modeled, and off-design performance of balance-of-plant components is evaluated through the use of performance maps and flow correlations. Optimization is employed to minimize the levelized cost of storage (LCOS). These efforts determined that the floating piston tank concept significantly reduces the impact of tank dynamics on system design and performance, allowing efficient and reversible operation. Additionally, separate storage of water as a liquid yields lower costs and improved hardware compatibility relative to a system configuration that stores water as vapor with other exhaust gases. ReSOC system optimization indicates that a pressurized stack system with pre-storage water removal accomplishes a levelized storage cost of 16.4 cents/kWh-cycle, an energy density of 100 kWh per cubic meter, and round trip efficiency of 68.8%. These results are shown to compare well with re-dox flow and conventional battery technologies.
  • Experimental study of true triaxial stress-induced deformation and permeability anisotropy in sandstones, An

    Tutuncu, Azra; Baizhanov, Bekdar; Abass, Hazim H.; Katsuki, Daisuke (Colorado School of Mines. Arthur Lakes Library, 2016)
    Determination of stress-induced anisotropy of reservoir mechanical properties is essential for a number of areas that can be collectively termed as drilling risk reduction and optimization of well and reservoir productivity. Borehole stability, well completions, hydraulic fracturing, and production operations require correct analysis of deformational behavior under a general stress state (σ_1≥σ_2≥σ_3). Current attempts to capture the effect of stress state on rock deformational characteristics typically consist of conventional triaxial testing of core samples. However, there still remains an absence of experimental results on stress-induced anisotropy of deformational properties performed under true triaxial stress state. Such stress conditions allow for independent manipulation of three principal stresses and consequently, studying of the stress-induced anisotropy of static deformation, acoustic wave velocities, permeability, resistivity, and other anisotropic properties under a variety of stress states and magnitudes. A novel true triaxial testing apparatus was designed and built by Dr. Ali I Mese of Geomechanics Engineering and Research, PLLC, and has been loaned to UNGI to conduct measurements under realistic in-situ reservoir conditions using cylindrical cores samples. This study was performed to capture the true triaxial stress effects on the deformational and flow behavior of reservoir rocks. The apparatus has been calibrated and used to study the influence of realistic stress anisotropy on static deformation, acoustic wave velocity, and permeability in sandstone core samples. Through shear stress cycling at various b parameter values and octahedral normal stresses, it was determined that stress-induced anisotropy is a function of closing and opening of microfractures oriented normally to increasing stresses. Changes in the nondimensional stress parameter b, signifying the relative magnitude of intermediate principal stress to maximum and minimum stresses, influence the mechanical behavior of rock in both dry and water-saturated conditions. Permeability measurements in the axial direction also display a dependence on magnitude and state of stress.
  • Kinematics and growth of supra-salt fault systems: a field and subsurface analysis, Salt Valley salt wall, Paradox Basin, Utah

    Trudgill, Bruce, 1964-; Horne, Elizabeth; Carr, Mary; Hearon, Thomas E. (Colorado School of Mines. Arthur Lakes Library, 2016)
    Salt can provide the structure and seal necessary for hydrocarbon entrapment. However, it may lead to structural complexities, such as compartmentalizing a hydrocarbon reservoir through supra-salt faulting. Outcrop analog studies provide exceptional opportunities to observe how salt-influenced fault geometries evolved spatially and temporally. The Salt Valley salt wall in the northern Paradox Basin is an exceptional location to study supra-salt faulting due to the proximity of world-class outcrops and a 3D seismic reflection dataset. This proximity enables fault slip kinematic information from outcropping fault surfaces to be assigned to 3D fault geometries mapped in the subsurface. The Salt Valley supra-salt fault array is approximately 40 km long, trends parallel to and detaches downward onto the NW-plunging salt wall. Integration of 3D seismic reflection data, wells, published maps, satellite imagery, and structural field measurements enabled the interpretation of the spatial and temporal evolution of the fault array. Several kinematic analyses coupled with detailed geometric fault descriptions were used to determine the growth history of the studied subsurface fault array, which consists of a series of overlapping fault segments up to 12.5 km long, with throws of hundreds of meters, defining a series of crestal grabens and half-grabens. Outcropping faults are of similar length, though offset from the subsurface study by approximately 500 meters. This proximity facilitates field to subsurface correlation. Along the strike of the fault array, there are notable changes in the dip direction of the half-graben master faults and regions of varying fault strikes. These changes reflect heterogeneities of the top-salt geometry. Fault linkage analyses such as: fault throw-length (T-L); throw-distance (T-x); throw-depth (T-z), as well as qualitative distribution of fault throws from map and strike views indicate that the subsurface fault segments are over-displaced and have complex fault segment linkage histories. This over-displacement may be evidence for a hybrid fault growth model, where faults initially grew per the isolated fault model, but spent much of their growth history through coherent fault growth. Additionally, faults analyzed in this study display non-fractal throw distribution, indicating that faulting is controlled by localized zones of strain that coincide with asymmetries in Top-Paradox Salt.
  • Model for acute stage HIV infection, A

    Pankavich, Stephen; Neri, Nathan J.; Diniz Behn, Cecilia; Nicholas, Michael (Colorado School of Mines. Arthur Lakes Library, 2016)
    This document lays out a new within-host model of acute stage HIV infection. The acute stage of HIV infection is characterized by a sudden spike of viral load, followed by either complete clearance of the disease or a low level but persistent chronic infection. Clinical data suggests that the initial concentration of healthy T-cells and virions is vital to the dynamics of this early stage, but this is not well modeled by the standard three component model. More nuanced models have had better success at representing the spread of HIV at all stages, but include many awkward biological components and are infeasible to fit to actual data. The model in this document incorporates the homeostatic nature of the immune system to provide a model for the acute stage of the disease which represents interesting nonlinear dynamics. Chief among these are bistable equilibria and a Hopf bifurcation within biologically relevant parameter regimes and dependent on initial conditions of infection. Local stability analysis of T-cell and virus populations to variation of parameters is also conducted, which leads to additional complexity in comparison to previous models.
  • Open-pit mine production scheduling under grade uncertainty

    Dagdelen, Kadri; Johnson, Thys B.; Van-Dúnem, Ady A. D.; Newman, Alexandra M.; Ozbay, M. Ugur; Kaunda, Rennie; Simões, M. Godoy (Colorado School of Mines. Arthur Lakes Library, 2016)
    Common challenges associated with grade uncertainty involve failing to meet decisive operational targets, which include (among others) the following: ore tonnage sent to the mill, total metal processed at the mill, blending requirements on ore feed, total waste tonnage mined, maximum allowable proportion of potentially deleterious materials (e.g., toxic elements such as arsenic). These challenges reflect, to an important extent, the uncertainty involved in defining precisely the mineral grades in an ore deposit. This has motivated a vast body of research directed at improving understanding stochastic mine planning techniques, with an aim of incorporating its tools to mine production scheduling. One popular paradigm for stochastic mine planning consists of formulating fully stochastic linear programming (SLP) models which adopt sets of realizations of the orebody to represent uncertainty regarding grades (Dimitrakopoulos et al., 2014). Since constraints must be met with total certainty, solutions from these formulations provide a decision maker with an absolute aversion to risk, i.e., one who (invariably) favors the most certain of two possible outcomes, regardless of their corresponding payoffs. Such production schedules may be too conservative in satisfying the production targets, while simultaneously producing sub-optimal results in those circumstances in which some flexibility in meeting targets exists. In a second paradigm, mine planners overcome the shortcomings of traditional production scheduling by incorporating geologic and grade uncertainty through geostatistical conditional simulations. However, this means that it is conceivable that one could also potentially benefit from any favorable development regarding previously “uncertain” domains of the ore deposit. The work undertaken in this dissertation focuses on generating production schedules that take into account grade uncertainty, as described by geostatistically simulated realizations of the ore deposit, and provide optimized production schedules that also consider the desired degree of risk in meeting the production planning outcomes. To do this, the production scheduling problem is formulated as a large-scale linear program (LP) that considers grade uncertainty as characterized by a resource block model. The large-scale LP problem is solved using an iterative decomposition algorithm whose subproblems are multi-time-period sequencing problems. At each iteration, one solves a master problem that generates a series of Lagrange multipliers (dual variables) that modify the objective function of the subproblems. In turn, the subproblem solutions modify the feasible region in the master problem and the approach is proven to converge to the optimal solution (Bienstock & Zuckerberg, 2009). The resulting LP solution is a multi-time-period mine production schedule that meets mining company’s required level of risk tolerance in mine production plans. The production scheduling formulation based on new risk-quantified linear programming models (LP) and their subsequent solutions do not only provide the risk profile of a given mine production schedule, but also allow the decision maker to define the level of acceptable risk in the mine plans generated and adopted
  • Characterization and restoration of inverted features across the southern Taranaki Basin

    Trudgill, Bruce, 1964-; Bucker, Wesley Shayne; Kuiper, Yvette; Sarg, J. F. (J. Frederick) (Colorado School of Mines. Arthur Lakes Library, 2016)
    The Southern Taranaki Basin is a predominantly offshore basin located between the two islands of New Zealand. The basin has a complex structural history due to its current location along an unconventionally shaped plate boundary and changes in a tectonic regime that have affected the basin over the last ~80 m.y. The focus of this study is the restoration and strain analysis of the Southern Taranaki Basin, which consists of the Central Graben and the Southern Inversion Zone. 2D and 3D seismic data sets are interpreted across the Southern Taranaki Basin using Schlumberger’s Petrel to create seven horizons that represent boundaries between significant structural events. The horizons and transecting fault surfaces are transferred to cross sections perpendicular to the major structures, which are each restored sequentially in 2D using Midland Valley’s Move. The restorations incorporate unfaulting, unfolding, and decompaction to measure the strain within each section and assess the overall distribution of strain within the Southern Taranaki Basin. Cretaceous extension associated with rifting and break-up of Eastern Gondwana shows a range of 8.1% - 0.8% extension along the cross sections. Localized basin extension in the Eocene (tied to the initiation of spreading between the Pacific and Australian plates in the southwest) resulted in a 1.9 - 0% extension. During the Oligocene-Miocene, Pacific Plate subduction beneath the North Island began to the northeast, resulting in 6.1 - 0.1% shortening. Within the last 7 m.y., as shortening continued in the south of the Southern Taranaki Basin, back-arc extension migrated from the north, resulting in up to 1.8% extension in the northern sections, up to 0.5% shortening across the southern end of the study area, and no strain in sections in the middle of the study area. Across the Southern Taranaki Basin, the net change along the lengths of individual sections range between 7.8% shortening and 2.7% extension. This study shows that the latitudinal transition of strain over time across Southern Taranaki Basin is not as uniform as previously assumed.
  • Potential of cross laminated timber in single family residential construction

    Pei, Shiling; Burback, Brad; Crocker, Joseph P.; Kiousis, Panagiotis Demetrios, 1956-; Davis, Graham A. (Colorado School of Mines. Arthur Lakes Library, 2016)
    Cross laminated timber (CLT) is a panelized engineered wood product that is gaining popularity in the United States as a structural material for massive timber buildings. CLT is shown to be cost competitive to steel and concrete in large building construction projects, but is seen as uncompetitive for smaller scale projects, especially light frame wood (LFW) residential construction. The purpose of this study is to provide a detailed comparison of the cost to construct a CLT home versus a LFW home to quantify the cost difference between both options in the single family home (SFH) market. Based on a realistic floor plan, three different designs were compared based on cost and construction timeline to determine the realistic cost differences between SFH constructions using LFW or CLT. The final results show that the CLT option results in a 21% increase in total construction cost from the LFW option. While it is difficult to justify this cost increase in Colorado, potential benefit of CLT construction against natural hazards may make a CLT house cost-effective for hurricane or tornado prone regions.
  • Integrated analysis of the growth history of the Moab-Spanish Valley salt wall and the Moab fault system, An

    Trudgill, Bruce, 1964-; Hissem, Anna; Kuiper, Yvette D.; Carr, Mary (Colorado School of Mines. Arthur Lakes Library, 2016)
    The Paradox Basin is a structurally unique and important petroleum basin in southeastern Utah and southwestern Colorado that provides pristine examples of diapiric salt structures and supra-salt faulting. The structural and stratigraphic architecture of the Paradox Basin was strongly influenced by the complex, dynamic evolution of the evaporite-rich Paradox Formation and development of NW trending salt wall structures. The Moab Fault System is one of the largest normal fault structures within the Paradox Basin and provides an ideal opportunity to study the linked evolution of salt structures and supra-salt faulting. The fault system trends parallel to the Moab-Spanish Valley salt wall, extending approximately 30km NW of the entrance to Arches National Park. Although the fault system has been extensively studied, the timing and mechanisms controlling faulting are not well understood. The literature presents a range of inconsistent dates for fault initiation, ranging from the Permian through the Quaternary, while extensional mechanisms include regional extension, salt evacuation, and salt dissolution. This study reveals new information and conclusions regarding the development of the Moab Fault System and the underlying Moab-Spanish Valley salt wall, answering questions that were previously in debate. Detailed mapping along the Moab Segment and Mill Canyon Linkage Zone of the Moab Fault System characterize important hanging wall structures: collapse v-shaped synclines on the limb of a rollover anticline along the southern portion of the Moab Segment and extensional fault tip monoclines along the northern portion of the fault system. The synclines and monoclines indicate brittle, post-depositional faulting. Kinematic data indicate primarily dip-slip fault motion with oblique slip concentrated along fault branch points and curved fault segments. Extension is towards the NW along the NE-striking Moab Segment, transitioning to mainly northward extension along the E-W striking segments of the Mill Canyon Linkage Zone. A series of closely spaced 2D cross sections and 3D surfaces were constructed by integrating detailed surface data with all available subsurface data including wells, one 2D seismic profile, published 2D cross sections, and published structure contours. The interpreted 3D geometries reveal a lack of evidence for growth faulting and a genetic relationship between the shape of the top of the underlying Paradox Formation and localized fault initiation. Throw distributions indicate that the highest point of the underlying asymmetric salt high, or pillow, corresponds to the maximum throw and the location of fault initiation of the Moab Segment. Additionally, the faults along the Mill Canyon Linkage Zone are located where the top of the Paradox Formation increases in slope, dipping to the north. These data suggest that the fault system developed after the formation of the diapiric salt structures and deposition of the strata exposed in the field, at a minimum (early Cretaceous). This study also suggests salt movement from beneath the hanging wall as a stronger candidate for fault initiation than regional extension due to the lack of additional large-scale normal faults (graben system) in the area surrounding the Moab Fault System, indicating more localized strain than expected during regional extension. Faulting may have initiated due to uplift of the CO plateau during the late Neogene, which substantially increased erosion and initiated salt dissolution along the Moab-Spanish Valley salt wall. This process would have lowered the differential pressure on the Paradox Formation evaporites along the salt wall, forcing salt to migrate away from the thick overburden surrounding the salt structure (high differential pressure) towards the main salt wall and thinner overburden (low differential pressure). The presence of cataclastic deformation bands across the fault system provides evidence for deformation at a substantial burial depth and, therefore, before complete uplift and exhumation. This proposed deformation mechanism suggests that the brittle hanging wall accommodated the evacuation of the underlying Paradox Formation through the initiation of the Moab Fault system.
  • Seismic waveform modeling and inversion in acoustic orthorhombic media

    TSvankin, I. D.; Wang, Hui; Snieder, Roel, 1958-; Li, Yaoguo (Colorado School of Mines. Arthur Lakes Library, 2016)
    Three-dimensional seismic waveform inversion (WI) for anisotropic media is highly challenging due to its computational cost, large number of model parameters, and parameter trade-offs. In this thesis, I explore 3D waveform inversion for orthorhombic media in the acoustic approximation. Two mixed-domain seismic wavefield simulators are implemented; one of them is based on low-rank decomposition and the other on the generalized pseudospectral method. Both methods can produce kinematically accurate pure-mode P-wavefields with an acceptable computational cost. The low-rank-decomposition-based method is used to simulate both state and adjoint wavefields due to its higher accuracy and stability. The wave equations from the pseudospectral method are employed to obtain the gradients of the WI objective functionals. To build the initial long-wavelength model for waveform inversion, I use an envelope-based misfit functional, which alleviates the reliance of WI on low-frequency data. The WI gradients are derived for both the conventional data-difference and the envelope-based objective functions. Numerical examples illustrate the performance of the developed wavefield-extrapolation and gradient-computation algorithms for orthorhombic media with realistic complexity. WI is conducted with the help of a limited-memory version of the quasi-Newton optimization algorithm. A test for a modified version of the SEG/EAGE overthrust model validates the proposed approach to waveform inversion in acoustic orthorhombic media.

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