• Fundamental surface chemistry and froth flotation behavior using quebracho tannins

      Anderson, Corby G.; Rutledge, Jordan; Spiller, D. Erik; Taylor, Patrick R. (Colorado School of Mines. Arthur Lakes Library, 2016)
      With an increasing emphasis on minimizing the impact and downstream treatment of metallurgical processes, a focus on utilizing less harmful and easier to handle reagents is occurring. Tannins, a naturally occurring, non-toxic reagent, have shown promise in metallurgical and mineral processing applications. This research was performed to investigate the use of tannins (specifically two types of quebracho: Tupasol ATO and Tupafin ATO) in the froth flotation process as a depressant for gangue minerals. Two ore types, copper and fluorite, were researched. The primary gangue mineral of interest was calcite for the fluorite ore, while it was pyrite for the copper ore. Surface chemistry studies including zeta potential, adsorption density, and microflotation were undertaken to provide fundamental knowledge about the behavior of tannins interacting with the mineral surface. Adsorption studies indicate that the mechanism for Tupasol ATO adsorption onto calcite and fluorite surfaces is chemisorption, as an increase in adsorption occurred with increasing temperature. The same adsorption behavior is true for Tupafin ATO adsorption onto pyrite surfaces, although Tupafin ATO adsorption did not increase with increasing temperature onto chalcopyrite surfaces, suggesting the adsorption mechanism may be physical. Thermodynamic calculations for adsorption including Stern-Grahame free energy, entropy and enthalpy were determined. All four minerals tested were found to be thermodynamically favorable. Fluorite, calcite, and pyrite were endothermic in nature, while chalcopyrite was found to be exothermic. Microflotation experiments were completed on pure minerals to determine the suitable operating parameters for bench flotation; a number of statistical models were generated to predict the outcomes of changing parameters. Three different tannins (Tupasol ATO, chestnut, and wattle) were compared for the microflotation of calcite and fluorite; Tupasol ATO was found to have the best performance. Bench flotation was performed on three different ores, a Mexican fluorite ore, a Peruvian copper ore, and Morenci copper ore. With the addition of Tupasol ATO, the recovery and grade of the fluorite concentrate was seen to increase. Tupafin ATO was shown to provide a dramatic increase in recovery and doubling the grade for the Morenci copper concentrate. Tupafin ATO also demonstrated a positive effect on the grade and recovery of the Peruvian copper ore. This suggests that tannins not only work as a depressant but as a dispersant. An economic analysis was completed to explore some of the fiscal benefits of using tannins for froth flotation.
    • 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
    • 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.
    • Valuation of ecosystem services impacted by mine site pollution

      Balistreri, Edward J. (Edward Jay); Gulley, Andrew L.; Eggert, Roderick G.; Fell, Harrison; Miller, Hugh B. (Colorado School of Mines. Arthur Lakes Library, 2016)
      While mine site pollution is well regulated in developed countries, regulatory agencies have started to value its environmental impact to gain a better understanding of the trade-offs between mineral development and environmental quality. Ecosystem service valuation incorporates the value of ecosystem services into decisions regarding abandoned mine lands, legacy sites, operating mines, proposed mine development, and mine closure. Benefit transfer provides an attractive ecosystem service valuation method that applies valuation results, from the environmental valuation literature, to sites in need of valuation estimates. This dissertation constructs a benefit transfer model to value mine site pollution and applies it to mine sites around the world. The results illuminate the benefits of a Superfund remediation and the impacts of artisanal and small-scale mining.
    • Experimental and numerical analysis of heat transfer in unsaturated soil with an application to soil borehole thermal energy storage (SBTES) systems

      Smits, Kathleen M.; Moradi, Ali; McCartney, John S.; McCray, John E.; Wu, Ning; Yin, Xiaolong (Colorado School of Mines. Arthur Lakes Library, 2016)
      A promising energy storage option is to inject and store heat generated from renewable energy sources in geothermal borehole arrays to form soil-borehole thermal energy storage (SBTES) systems. SBTES systems involve direct circulation of heated fluid through closed-loop geothermal heat exchangers in closely spaced vertical borehole arrays. Although pilot programs are successfully utilizing SBTES systems, two of the main limitations in large-scale implementation of these systems are low system efficiency and high initial installation costs. An approach to potentially enhance the efficiency of SBTES systems is to install them in the vadose zone (the unsaturated zone of soil above the water table). In this case, it is possible to take advantage of phase change and convective heat transfer phenomena in the pore water to obtain greater heat injection and extraction rates, making the SBTES system more efficient. Although it is widely recognized that the movement of water in liquid and vapor forms through unsaturated soils is closely coupled to heat transfer, these coupled processes have not been considered in modeling of SBTES systems located in the vadose zone. Instead, previous analyses have assumed that the soil is a purely conductive medium with constant hydraulic and thermal properties. The goal of this dissertation was to better understand heat and mass transfer processes with an application to SBTES systems installed in the vadose zone through conducting experimental and numerical studies in different scales. To achieve this goal, three different phases using both experimental and numerical investigations are defined. The experimental study included both two- and three-dimensional bench and intermediate scale experiments, respectively. Experimental data were then used to validate a numerical model that solves for water and vapor flow and considers non-equilibrium phase change. In addition, a set of pore-scale numerical simulations using the phase field method were defined to study soil thermal and hydraulic properties. 2-D experimental and numerical results demonstrated the importance of simultaneously analyzing coupled heat and mass transfer in SBTES systems installed in the vadose zone. For the initial and boundary conditions assumed in the study, results indicated that convective heat flux is considerably larger than conductive heat flux, demonstrating the importance of including convective heat transfer in modeling of SBTES systems, especially in the unsaturated soils where water vapor is present. Results of the 3-D study revealed that for the test conditions studied, convective heat transfer was higher than conductive heat transfer in the middle of the borehole array. Moreover, for experiments with unsaturated sand, about 10% of the total heat transfer was in the form of latent heat. Simulation results demonstrated the importance of including both convection and latent heat in SBTES system modeling. Results also revealed a need for implementing saturation-dependent effective thermal conductivity in SBTES numerical models rather than using constant values such as those obtained from system thermal response tests. Pore-scale simulations provide opportunities to understand the impact of smaller-scale phenomena on larger scale processes. Pore-scale simulation of heat conduction through unsaturated porous media showed an abrupt decrease in thermal conductivity at approximately 60% saturation. This abrupt decrease is most likely due to the disconnection of water-soil connections or “bridges” which in turn, diminished heat transfer through highly conductive water - soil pathways while the less conductive air - soil pathways dominated. In fact, a 4% decrease at approximately 60% saturation reduced the effective thermal conductivity by more than 30%. The pore scale model can be used to perform sensitivity analysis on several important properties, evaluate thermal and hydraulic properties in elevated temperatures and asses the validity of thermal-equilibrium assumption in continuum-scale models.
    • Numerical analyses of the long term behavior of enhanced geothermal system (EGS)

      Nakagawa, Masami; Arshad, Hafiz Syed Mahmood; Griffiths, D. V.; Holley, Elizabeth A.; Kaunda, Rennie (Colorado School of Mines. Arthur Lakes Library, 2016)
      Enhanced Geothermal System (EGS) technology is a challenging extrapolation of conventional hydrothermal geothermal systems but expected to significantly contribute to U.S. energy in near future. This technology is still going through a steep learning phase and current research studies are mostly focused on reservoir performance and initial stages of the EGS. The main focus of this research is to gain a better understanding of thermal stresses generated during the heat recovery process as a result of induced cooling of rocks and interaction of thermal stresses with existing lithologic stresses. The long term behavior of the EGS is assessed in terms of stress redistribution and reservoir performance based on selected operation, design, and geologic variables. Existing concepts of stress generation and redistribution are revisited, improved and supported with numerical models. Eighteen different models are developed using COMSOL, a finite element numerical modeling environment, based on the three study variables, i.e., production rate, number and pattern of boreholes, and thermal properties of rock, to provide scenario comparisons, effect quantification, analytical reasoning, and factual explanations. The three study variables are found to be functioning interdependently to define the performance and the final stress state of the EGS. Production rates are shown to delineate rates of heat removal, number and pattern of injection and production borehole(s) are shown to define flow paths, and thermal properties of rock are shown to have control over heat flows. Magnitudes of thermal stresses generated are found to be 35 to 45 MPa; stress redistribution is shown to relieve applied in-situ stresses by magnitudes equal to the tensile thermal stresses. The findings of this study provide original quantification of stress redistribution in the EGS with respects to study variables. Outcomes of this research will serve as a foundation for assessing the long term effects of the EGS and the extent of the effects on the surrounding rock mass. Also, considering the acceptable magnitudes of stresses produced by full scale numerical models of multiple EGS scenarios, the EGS is suggested to successfully and safely fulfill a portion of our future energy needs.
    • Multi-physics model for enhanced oil recovery in liquid-rich unconventional reservoirs, A

      Tutuncu, Azra; Bùi, Bình Thanh; Mustoe, Graham G. W.; Davis, Thomas L. (Thomas Leonard), 1947-; Batzle, Michael L.; Kazemi, Hossein; Ozkan, E. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Abstract Because most of the hydrocarbon remains trapped in the reservoir, recovery factors for tight oil and shale oil are very low. Recovery factors for these formations typically range from 3 to 7%. Since shale matrix has very low permeability, conventional reservoir simulators often overestimate the mass exchange between shale matrix and fractures. To evaluate the potential of water injection for improving oil recovery, the mass transport in the reservoir at different scales should be modeled properly. These issues have motivated us to conduct this research study to evaluate the potential of water injection enhanced oil recovery in liquid-rich unconventional reservoirs accounting for the effects of salt concentration, fluid type, shale swelling, and wettability alteration. There are several mechanisms for the imbibition of water into the rock matrix. In pore scale modeling, it was shown in this research that the interfacial tension-induced transport is one of the key mechanisms contributing to the transport of oil trapped in the pores. The change in the interfacial tension and the contact angle results in wettability alteration and can be interpreted as one of the key factors for imbibition of water into the rock matrix, especially in oil-wetted matrix blocks as observed in laboratory experiments. The amount of oil recovery varies for various ion types, indicating an effect of ion type on the oil recovery. This original pore scale modeling study helps us to evaluate the contribution of interfacial tension-induced transport on the imbibition of water into pores. However, upscaling from pore scale to a larger scale requires further studies for a true representation of the reservoir conditions. Hence, while a new pore scale model was introduced in our research study, it is not fully incorporated in the matrix block and reservoir scale models presented in this study. In a matrix block scale model, a phenomenological model for mass exchange between the rock matrix and the fractures was formulated to compute the mass transfer used in reservoir scale model. This mass transport model was validated using experimental data. A shale swelling model was also derived to account for the swelling effect on the matrix and fracture permeability and porosity by solving the coupled geomechanics and mass transport models. The coupled fluid flow and geomechanics model was solved for every matrix block within the reservoir scale model to evaluate the overall effect of salt concentration, shale swelling, and wettability alteration on oil recovery. The matrix block scale simulation results indicate that osmosis is an important force imbibing water into low permeability rock matrix and enhancing the effectiveness of low salinity waterflooding on oil recovery. The imbibition of water into oil-wetted shale matrix is mainly driven by the osmotic transport and wettability alteration. The contribution of osmotic transport continues for a long period of time and contributes to oil production if the membrane efficiency is high and the matrix block size is small. However, the low membrane efficiency of the shale formations, typically less than 10%, considerably reduces the contribution of osmosis on oil recovery. The effect of fluid type on the oil recovery depends on the membrane efficiency and the diffusion coefficient of the ion. Higher membrane efficiency and lower diffusion coefficient of dissolved ions increase the contribution of osmosis on the oil recovery from shale matrix. Matrix swelling decreases matrix and fracture porosity, forcing the fluid out of the rock matrix and maintaining the pressure in fracture. However, matrix swelling significantly reduces the permeability of the matrix and fractures, reducing oil recovery. Therefore, water injection is not recommended for formations with high swelling potential. Further research on wettability alteration and membrane efficiency variation is recommended for enhanced oil recovery operation in liquid-rich unconventional reservoirs.
    • Effects of thermomechanical processing and annealing on the microstructural evolution and stress corrosion cracking of alloy 690, The

      Kaufman, Michael J.; Miller, Cody A.; Field, Robert; Bourne, Gerald; Findley, Kip Owen; Berger, John R. (Colorado School of Mines. Arthur Lakes Library, 2016)
      The effects of short-range order (SRO), long-range order (LRO), and plastic strain on the microstructure and stress corrosion cracking (SCC) susceptibility of Ni-Cr-Fe Alloy 690 have been investigated in detail. First, the presence of 1/3{422} and 1/2{311} diffuse intensities in B=[111] and B=[112] selected area diffraction patterns (SADPs), previously believed to indicate the presence of SRO, has been examined in Alloy 690, a Ni-Cr binary alloy, and a number of FCC materials in an effort to determine their source. It is shown that these intensities are not due to SRO, although their source remains somewhat unclear. However, an experiment was conducted that tracked the strong {111} reflections in a B=[112] SADP as the sample was tilted (19°) towards a B=[111] zone axis. Significantly, it was noted that the {111} intensities never fully disappear and that they fall in the 1/3{422} positions within the B=[111] SADP. This indicates that these diffuse intensities are related to reflections that lie in the first order Laue zone (FOLZ) when the zone is aligned along B=[111], although theoretical calculations indicate scattering from these planes into the zero order Laue zone used to form the SADP should not occur. Thus, while calculations are inconsistent with the behavior expected, the diffuse intensities observed in a number of high index zones are consistent with projections of higher order Laue zone reflections into the zero layer, suggesting that the theory is in need of reassessment. Second, the stability of the γ’-Ni2Cr LRO phase present on the Ni-Cr phase diagram was examined in a Ni-55Cr binary alloy. The results indicate that the γ’-Ni2Cr phase is indeed metastable, and that the two-phase γ-Ni + α-Cr phase field extends all the way to room temperature. Likewise, the sluggish formation of the γ’-Ni2Cr phase appears to occur only over a narrow composition and temperature range. It is speculated that this important phase in more complex alloys is also metastable and its metastability should be considered in applications involving long-term, high temperature exposures. Third, the effects of thermomechanical processing and long-term aging on the microstructural evolution and SCC susceptibility of Alloy 690 were examined in detail. It is shown that cold working and subsequent aging have large impacts on the microstructures observed and on the mechanical properties, and it is these changes that are related to the differences in SCC behavior. Most importantly, it is shown that the very high work hardening in Alloy 690 leads to large increases in yield strength that appear to overshadow the more subtle variations in carbide distributions at grain boundaries and prior coherent twin boundaries, and that SCC initiation is difficult if not impossible under static loading conditions. Based on these observations, it is concluded that the long-term concerns by industry of SCC initiation in Alloy 690 in the thermally-treated condition can probably be ignored unless there are regions where the alloy has been significantly hardened mechanically and the material will undergo some type of dynamic loading.
    • Tectonostratigraphic evolution, seismic interpretation and 2D section restoration of the offshore eastern Otway Basin, Victoria, Australia, The

      Trudgill, Bruce, 1964-; Hazar, Mehmet; Sonnenberg, Stephen A.; Sarg, J. F. (J. Frederick) (Colorado School of Mines. Arthur Lakes Library, 2016)
      The Otway rift basin is located on the northwest trending passive margin that extends from southeast Australia to the neighboring the Sorell Basin, west of King Island. The formation of the Otway Basin is associated with the breakup of Gondwana during the late Jurassic/early Cretaceous, and the basin comprises two rifting and multiple inversion events reflected by eight basin supersequences. The basin contains sediments deposited from Upper Jurassic to Holocene and the extent of the basin is 150,000 km2, of which 80% lies offshore. Although the eastern Otway Basin has been investigated in both the onshore and the shallow marine section, a tectonostratigraphic framework for the offshore part still needs to be developed in detailed explanation, which will be rewarding for hydrocarbon exploration purposes. This study aims to interpret and reconstruct the structural evolution of the Otway Basin by integrating tectonostratigraphy, well data, 2D seismic profiles, 3D seismic cubes, and 2D structural restorations. Seismic interpretation is performed for each 3D seismic survey by creating structure maps and labeled seismic profiles. Regional structure maps were also generated at each individual basinal phase by using 2D & 3D seismic data together to apply seismic interpretation techniques. Schlumberger`s Petrel software is used for structural and stratigraphic interpretation on 2D and 3D seismic data set provided by Geoscience Australia whereas Midland Valley`s Move software is used for 2D kinematic reconstruction and restoration throughout the basin. Structural characteristics and depocenter developments for rifting phases, fault types, quantification of extension amounts and designation of regional deformation model is conducted within the scope of this study. Different structural trends composed due to two separate rifting phases are mapped and investigated through seismic profiles and four cross sections restored from Investigator 3D Survey from the Offshore Eastern Otway Basin used to calculate extension amounts (IL 300 - 6.63% [2.626 km], IL – 700 11.11% [5.56 km], IL – 1150 11.16 % [5.63 km], IL – 1700 11.05% [5.53 km]). In addition, regional lithospheric extension model is determined by comparing and contrasting with the existed deformation models.
    • Petrophysical rock typing of unconventional shale plays: a case study for the Niobrara Formation of the Denver-Julesburg (DJ) Basin

      Prasad, Manika; Kamruzzaman, Asm; Davis, Thomas L. (Thomas Leonard), 1947-; Ozkan, E.; Brieg, Jack (Colorado School of Mines. Arthur Lakes Library, 2016)
      A petrophysical rock typing has been performed based on a methodology that integrated depositional and petrophysical rock analysis to identify distinct rock types in the Niobrara Formation of the Denver-Julesburg (DJ) Basin. The depositional rock analysis incorporated a literature study, interpretations of the geologic depositional setting and sequence stratigraphy, core descriptions, and analysis of well-log data. The petrophysical rock analysis was carried out using experimental core data on mineralogy, pore characterization, source rock evaluation, micro-textural image analysis, and ultrasonic acoustic velocity and anisotropy interpretations. Six Niobrara Formation lithofacies and three similar lithofacies-groups (All Marls, Middle Chalks, and Basal Chalk) were identied in the target well interval through the depositional rock analysis within the context of the large-scale geologic framework. The pore-scale petrophysical rock analysis was carried out to investigate whether these lithofacies-groups followed distinct rock types in the Niobrara Formation based on the analysis of experimental core data. The conclusions reached in this study included that, based on the mineralogy, pore structure, and acoustic velocity interpretations, the Basal "Chalk" may be a Basal Marl - at least locally in the studied target well. However, the Basal Chalk rocks contain lowest source rock potential and are not likely to contribute to economic hydrocarbon production for the target well. Both the All Marls and the Basal Chalk rock-groups have higher porosity, smaller pores, and smaller pore throats than the Middle Chalks. The rocks in the Middle Chalks have higher stiffness and pressure compliant pores. The Niobrara Formation is an unconventional petroleum system - its hydrocarbon-rich mudrock units were deposited in a shallow marine environment and have evolved as oil- and gas-prone source and reservoir rocks. Significant pore-scale variability in mineralogy, pore characterization, organic matter distribution, and acoustic velocity and anisotropy properties exist in these rocks. Hydrocarbon production from its low-porosity, nanodarcy permeability, and interbedded chalk-marl reservoir interval is very challenging. The petrophysical rock typing methodology adopted in this case study can be a useful formation evaluation tool for the Niobrara Formation. It can provide valuable information about its rock matrix, such as, the lithofacies identification and descriptions through depositional rock analysis, identifying reservoir and sourcing intervals, mineralogy analysis, organic matter evaluation, pore characterization, and acoustic velocity and anisotropy properties.
    • Making theoretical chemistry useful to practicing chemists as researchers and educators

      Eberhart, Mark E.; Miorelli, Jonathan T.; Moskal, Barbara M.; Caster, Allison G.; Vyas, Shubham; Wu, David T. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Chemistry is concerned with understanding and predicting the interactions and properties of matter. A valuable tool towards this goal is Density Functional Theory, which asserts that all ground-state properties can be determined using the charge density alone. Conceptual Density Functional Theory (CDFT) has given rigorous definitions for a variety of chemical concepts such as electronegativity and chemical hardness, though use of these definitions often requires knowledge of the system beyond just the ground-state charge density. Applied Density Functional Theory (ADFT) seeks to extract these same chemical properties from computed or experimental charge densities alone. ADFT also seeks to be "applied" by making theses charge-density analyses accessible and useful to practicing chemists. The first section of the thesis shows how ADFT is able to address problems currently present within the theoretical community. Researchers are developing conceptually based models linking the structure and dynamics of molecular charge density to properties. Key among these has been the discovery and description of the bond path and bond critical point from the Quantum Theory of Atoms in Molecules (QTAIM). The discovery of bond paths in systems not considered to be chemically bound – e.g. a H-H bond between adjacent hydrogens in a di-benzene complex and He-C bonds in the He + adamantane inclusion complex – seemed to pose a considerable challenge to analyzing bonding via topological analysis of the charge density. Using extensions to QTAIM developed by the Molecular Theory Group one can use a molecule’s ridges to define a natural simplex over the charge density. The resulting simplicial complex can be represented at various levels by its 0, 1, and 2-skeleton (dependent sets of points, lines, and surfaces). The geometry of these n-skeletons retains critical information regarding the structure and stability of molecular systems while greatly simplifying charge density analysis. Via the geometry of these n-skeletons one can uncover the fingerprints of instability and metastability in the systems mentioned above: the di-benzene complex and He + adamantane inclusion complex. The second section of the thesis investigates how "nearsighted" the charge density is and the significance of this nearsightedness. As has been demonstrated by Kohn and others, the charge density is "nearsighted" in that beyond some distance R from a test point, r0, any change to the external potential will only result in a small change in the change density at r0 ( Δρ(r0, R)). Two crucial questions are how large is R for a given system and how small of changes at r0 are small enough to be considered insignificant? To address this problem organic functional groups are used as a model of how much the charge density can change while still retaining a characteristic chemistry. The calculations presented below demonstrate that for halogen substitution on oxygen-containing functional groups the overall magnitudes of Δρ(r0, R) are all below 0.05-0.06 a.u. for the magnitude of charge at a bond CP and 0.3 a.u. for the curvatures at a bond CP. The effective radius beyond which halogen substitution no longer had a noticeable effect was on the order of two carbon bond-lengths (~3 Å). Values for Δρ are shown to be robust across a variety of DFT functionals and provide a framework for the transfer of the functional group concept other disciplines, such as metallurgy. The final section demonstrates how the concepts of ADFT can be adapted in a way that allows students to make use of the charge density. For instance, the chemical bond concept is the foundation of the molecular sciences in general and ADFT specifically. As such, helping students gain a clear physical representation of chemical bonding is necessary for the progress of ADFT. Bond Explorer, an activity that utilizes the 3D plotting functionality of Mathematica, is intended to provide a clear physical picture of electron sharing among atoms – i.e. a physical picture of the chemical bond. The activity was designed in accordance with the best practices of scientific teaching with a focus on active learning and peer-instruction. Through the course of the activity, students visualize the 3D charge density using both fog and contour plots. Students then go on to describe the density differences that characterize various bonding types, i.e. covalent, polar-covalent, and ionic. The activity involves independent work at home prior to class to provide exposure to the material prior to the in-class portion of the activity. In-class, a short review lecture is followed up by group work where students identify key similarities and differences in the charge density corresponding to various bond types. The in-class portion of the activity involves students working on concept-focused open-ended questions in small groups, to better encourage peer-instruction. Analysis of exam scores from the fall 2015 CHGN 121 revealed that students who participated in the activity performed better on the first two exams following participation in the activity (t-test at 95% confidence). A short quiz focused on Bond Explorer was administered before and after students participated in the activity in the summer 2016 section of CHGN 121 showed that students did perform better on the quantitative portion of the quiz (Wilcoxon signed-rank test at 90% confidence). Analysis of the qualitative portion of the quiz revealed possible misconceptions about bonding that will be addressed in further versions of Bond Explorer.
    • Use of chain growth polycondensation via substituent effects for the development of new polymer brush systems

      Boyes, Stephen G.; Prehn, Jr., Frederick C.; Knauss, Daniel M.; Sellinger, Alan; Zimmerman, Jeramy D. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Polymers are extensively used as the main component of many coating technologies. Attachment strategies to produce polymer films with advanced functionalities have evolved from a top down technique to embody more of a bottom up approach, where thin films are actually grown from the substrate of interest. This grafting from technique has allowed for the development of polymer films with advanced architectures and improved functionality through the use of controlled/living radical polymerization (LRP) techniques that produce random coil polymers. These polymers, however, are unable to exhibit properties that polymers with more rigid character possess. The ability to produce brush films with polymers that are more elongated and have the ability to order with one another in a more of a crystalline arrangement offers the opportunity to create polymer brush films with impressive new performance properties. In order to prepare brushes from rigid polymers, it is imperative to employ a chain growth condensation (CGC) polymerization technique in place of the more conventional step growth method. The two procedures employed to achieve CGC are the activation/deactivation method through the use of substituent effects and the catalyst transfer technique used in cross coupling reactions. To date, only conjugated polymer brushes employing catalyst transfer reactions have been produced. There remains a wide variety of high performance polymers that have yet to be used in polymer brushes that can be made via the CGC process. One particular type of condensation polymer, poly(aromatic amides) or aramids, has the potential to expand the role of polymer brushes into new and exciting areas. The main goal of this dissertation is to achieve the first examples of aramid brushes using substituent effect CGC. To this effect, the synthesis of well-defined, surface-initiated poly(N-octyl-p-benzamide) brushes was demonstrated using a novel grafting from surface initiated CGC technique. Issues with the thickness and solubility of these brushes sparked interest to further understand the factors that influence the preparation of poly(benzamides) using substituent effect CGC. Studies were conducted to investigate the role of the monomer ester substituents and initiator structure in the CGC polymerization. It was found that the monomer ester substituents play a major role in maintaining control over the polymerization, determine the overall reaction kinetics, and improving solubility of the reaction system. Experimental results and computational studies demonstrate that the overall effect of the monomer ester substituent is more dependent on the stability of the leaving group than the electrophilicity of the reacting carbonyl. Improvements upon the preliminary aramid brushes were realized by using the expanded understanding of the CGC technique through the use of substituent effects and has allowed for the creation of thicker brushes in a shorter time period. While, this thesis work documents the synthesis of the first aramid polymer brushes and provides a more comprehensive understanding of the substituent effect CGC process, there remains a great amount of work to further understand the structure and properties of the demonstrated brushes, in addition to expanding the work to new monomer structures.
    • Comparison of oil and intensive quenching via coupled thermal, transformation, and mechanical modeling

      Speer, J. G.; Baker, Daniel S.; Matlock, David K.; Van Tyne, C. J.; Thompson, S. W. (Steven W.); Mustoe, Graham G. W. (Colorado School of Mines. Arthur Lakes Library, 2016)
      A series of simulations were performed on a 25.4 mm (1 in) diameter 254 mm (10 in) long cylindrical bar. These simulations included three carburization levels: non-carburized, carburized to 0.8 wt pct C and 1.0 wt pct C at the surface utilizing a plain carbon steel (1020) and three alloy steels (4120, 4320, and 8620) representing a range of hardenabilities. Both industrially standard oil quenching as well as high intensity quenching which has a heat transfer rate of 20 kW/(m2 °C) were simulated. After quenching, the non-carburized and oil quenched bars were predicted to have tensile residual hoop stresses at the surface while the carburized bars were predicted to have compressive residual hoop stresses. All carburization levels of 1020 were predicted to have compressive residual hoop stresses after quenching. After high intensity quenching, all four alloys at all three carburization levels were predicted to have compressive residual stresses at the surface. It was shown that the high intensity quenching compressive residual hoop stresses at the surface were a result of the high heat transfer rate decreasing the temperature within fractions of a second resulting in a martensitic shell forming around a high temperature austenitic core. As the core cooled and thermally contracted, the shell was pulled inward to maintain coherency between the shell and the core. When the core austenite transforms, the volume expansion was insufficient to overcome the thermal contraction resulting in large compressive stresses at the surface and core, and a large tensile stress at the mid-radius. This profile was not found in literature. 1020 was found to transform to a mixture of ferrite and pearlite. As the core contracted and transformed, the volume expansion initially resulted in tensile hoop stresses near the surface. These tensile hoop stresses were decreased and became compressive due to the thermal contraction after transformation. A critical heat transfer rate for each of the alloys was determined where the tensile residual hoop stresses were reversed to compression. This critical heat transfer rate was 3.2 kW/(m2 °C), 9.0 kW/(m2 °C), 8.9 kW/(m2 °C), and 9.0 kW/(m2 °C) for 1020, 4120, 4320, and 8620 respectively. This was generalized to a Biot number with a minimum of 2.5 needed to create compressive hoop stresses at the surface.
    • Dissolved organic carbon (DOC) characteristics in metal-rich waters and implications for copper aquatic toxicity

      Ranville, James F.; Dee, Kato Tsosie; Wendlandt, Richard F.; Higgins, Christopher P.; Figueroa, Linda A.; McKnight, Diane M.; Walton-Day, Katherine; Smith, Kathleen S. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Acid Mine Drainage (AMD) originating from abandoned hardrock mines characteristically has high concentrations of potentially toxic metals, such as Cu, as well as dissolved and particulate forms of Al and Fe. Free copper (Cu2+) is a well-known contributor to heavy metal toxicity in aquatic systems. The bioavailability of Cu2+ is influenced by aqueous complexation, with humic (HA) and fulvic acids (FA) being especially important ligands. This research focused on examining changes in the binding affinity of fulvic acid (FA) that result from its chemical fractionation, which occurs by FA sorption to hydrous iron and aluminum oxides (HFO and HAO). FAs used in this study were collected from three alpine watersheds in Central Colorado (Upper Snake River, Colorado Gulch, and St. Kevin’s Gulch). Variability in spectroscopic properties of SUVA254 and fluorescence index (FI) was a result of chemical fractionation, watershed source, and season. Graphs of SUVA254 verses FI revealed FA from pristine waters shifts from characteristics of being aromatic, allochthonous in the spring/summer to less aromatic, autochthonous in the fall/winter. In the confluence where AMD impacted streams mix with the pristine streams, SUVA254 verses FI graphs show the effect of fractionation resulting in less aromatic FA. Measurements of Cu2+ in solution by an ion selective electrode (ISE) and acute copper toxicity tests (D. magna) revealed that FAs remaining in the water column after fractionation have less binding affinity and/or capacity than DOC in aquatic systems without the presence of HFO and HAO. FA fractionated in the laboratory, and under natural conditions (confluence sites) had lower acute copper EC50 values (20 to 96 µg Cu/L) than unfractionationed FA, suggesting a decrease in Cu binding affinity and/or capacity associated with fractionated FA. Site FA from pristine tributaries also had variability in EC50 values (48 to 146 µg Cu/L) that is likely related to variations in source and seasonality. The binding affinity of DOC is related to its aromaticity, which is characterized by SUVA254 for which low SUVA relates to lower binding capacity/affinity of DOC and a resulting higher concentration of Cu2+ in solution, as measured with a cupric ion specific electrode (ISE). Variability in DOC-Cu binding affinity in alpine AMD impacted watersheds is likely a significant factor in copper toxicity in aquatic systems and should be included in toxicological modeling programs such as the Biotic Ligand Model (BLM). Findings from this research suggest a further need to characterize DOC due to the inherit source variability and fractionation processes in AMD impacted watersheds. Therefore, additional work would better refine the BLM in order to accurately predict acute copper EC50 values, which are necessary to formulate water quality criteria in freshwater environments.
    • 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.
    • Pulse sliced picosecond ballistic imaging and two planar elastic scattering: development of the techniques and their application to diesel sprays

      Parker, Terence; Duran, Sean Patrick Hynes; Porter, Jason M.; Dreyer, Christopher B.; Hoff, William A.; Bogin, Gregory E. (Colorado School of Mines. Arthur Lakes Library, 2016)
      A line of sight imaging technique was developed which utilized pulse slicing of laser pulses to shorten the duration of the parent laser pulse, thereby making time gating more effective at removing multiple scattered light. This included the development of an optical train which utilized a Kerr cell to selectively pass the initial part of the laser pulse while rejecting photons contained later within the pulse. This line of sight ballistic imaging technique was applied to image high-pressure fuel sprays injected into conditions typically encountered in a diesel combustion chamber. Varying the environmental conditions into which the fuel was injected revealed trends in spray behavior which depend on both temperature and pressure. Different fuel types were also studied in this experiment which demonstrated remarkably different shedding structures from one another. Additional experiments were performed to characterize the imaging technique at ambient conditions. The technique was modified to use two wavelengths to allow further rejection of scattered light. The roles of spatial, temporal and polarization filtration were examined by imaging an USAF 1951 line-pair target through a highly scattering field of polystyrene micro-spheres. The optical density of the scattering field was varied by both the optical path length and number densities of the spheres. The equal optical density, but with variable path length results demonstrated the need for an aggressively shorter pulse length to effectively image the distance scales typical encountered in the primary breakup regions of diesel sprays. Results indicate that the system performance improved via the use of two wavelengths. A final investigation was undertaken to image coherent light which has elastically scattered orthogonal to the direction of the laser pulse. Two wavelengths were focused into ~150 micron sheets via a cylindrical lens and passed under the injector nozzle. The two sheets were adjustable spatially to allow probing of the sprays three dimensional structure. The test matrix included two nozzle diameters, 160 and 320 microns, and two fuels dodecane and methyl oleate. Results are presented comparing the fuels and the effects of nozzle diameter. A mathematical interpretation of the results is also presented.
    • Beamline improvements to the MInes NEutron Radiography (MINER) facility

      King, Jeffrey C.; Wilson, Clinton R.; Greife, Uwe; Deinert, Mark R. (Colorado School of Mines. Arthur Lakes Library, 2016)
      The Colorado School of Mines designed and installed a neutron radiography system at the United States Geological Survey TRIGA reactor (GSTR) in 2012. Several potential improvements to this system have since been identified, particularly with respect to the neutron beamline. This thesis details the design of a new beamline to address some of the drawbacks of the present system. Computational analysis using MCNP determined that a 7.32 m long, un-lined, square aluminum beam tube with a 1 m circular pre-collimator produces a neutron beam with a lower divergence than an equal length collimator that has a neutron absorbing liner and no pre-collimator. The placement of graphite around the pre-collimator can boost beam intensity by up to 15%. The new beamstop will require an additional 720 kg shielding to keep the radiation dose rates comparable to the present beamline. Structural analysis also showed that the new beamline design has a smaller tendency to bend (by ~90%) than the current tube, and has a maximum buoyant force of 29.5 kg that will need to be overcome through the addition of ballast.
    • Gob ventilation borehole design and performance optimization for longwall coal mining using computational fluid dynamics

      Brune, Jürgen F.; Bogin, Gregory E.; Saki, Saqib Ahmad; Griffiths, D. V.; Miller, Hugh B.; Kaunda, Rennie (Colorado School of Mines. Arthur Lakes Library, 2016)
      Longwall mining is a method used in underground coal mining, which is preferred by mine operators due to increased productivity and lower overall injury rates. Coal mines may be considered gassy based on the presence of hazardous gases like, methane, CO and CO2. In the United States, the Mine Safety and Health Administration (MSHA) considers all coal mines to be gassy as a safety measure. In longwall mines, gases from rider coal seams or the floor can migrate into the gob, which has the higher permeability, and then move forward to the working space and areas. The accumulation of methane gas is a safety hazard to the working environment as it can be explosive when mixed with oxygen and exposed to an ignition source. Coal bed degasification, ventilation, nitrogen injection, and gob ventilation boreholes (GVBs) are some of the methods used to control methane hazards. A well designed mine ventilation system, alone, is limited in its ability to manage methane emissions. When methane emissions are beyond the level that ventilation can handle, additional measures are required, like drilling vertical methane drainage holes, or GVBs, from the surface into the gob area to extract the methane gas; these boreholes are drilled from the surface, above the panel ahead of the mining activity. When the advancing face intercepts the GVBs, the boreholes begin producing methane. It is important to predict the performance of GVBs to ensure a safer working environment in longwall coal mining. The performance of GVBs depends on multiple factors, including; borehole locations, number of boreholes, length of slotted casing, diameter of casing, setting depth of casing above the panel, overburden strata, wellhead vacuum pressure, permeability of caved and fractured zones, and the area of influence of GVBs. GVBs are widely used in United States (U.S.) underground coal mines for longwall gob degasification. GVBs can recover 30 to 70% of methane emissions from the longwall gob depending on geologic conditions (Mutmansky, 1999). Generally, they are considered useful for reducing methane concentrations in working areas, thereby reducing explosion hazards and creating safer working conditions for a longwall section. The computational fluid dynamics (CFD) modeling work in this dissertation confirms that GVBs are helpful to reduce the methane concentrations at the face. However, they may also draw fresh air from the face into the gob; increasing oxygen ingress into the gob creates explosive gas zones (EGZs) within the gob. It is important to identify the locations for gob ventilation borehole placement to maximize methane extraction and minimize any explosion hazards. CFD models were developed for this dissertation to analyze the effects of GVB design and operating parameters for methane extraction, the formation of explosive gas zones in the gob and methane concentrations at the longwall face and tailgate. Parameters such as the distance of GVBs from the tailgate and the working face, the borehole diameter, the distance from the top of the coal seam being mined, the wellhead vacuum pressure and the number of GVBs operating on the panel, all have a significant effect on methane extraction, explosive gas mixtures volume and methane concentration in working areas. The CFD studies in this research identified optimal GVB design and operating parameters to maximize benefits and minimize risks. This research used the CFD modeling software package ANSYS® Fluent® along with the output of geomechanical modeling for permeability and porosity input into the CFD models. Earlier research at Colorado School of Mines developed the geomechanical models of the case study mines based on data received from cooperating mines, using the geomechanical software package FLAC3D to determine the permeability of the gob and fractured zone (Marts et al., 2014a; Wachel, 2012; Worrall, 2012). The main purpose of mine ventilation design is to provide sufficient quantity and quality of air to the workers, and to dilute the concentration of methane and other contaminants. A common perception among mining engineers is that additional air along the longwall face will improve methane dilution on the face and in the tailgate. In this dissertation, a parametric study is presented to discuss the effect of face air quantity on methane concentrations in the tailgate and formation of EGZs in the gob. Counter to conventional wisdom, increased longwall face air quantities may increase the explosion hazard as they result in higher EGZ volumes in the gob and increased methane quantities in the tailgate return. The results have been validated against the data provided by cooperating mines and also compared with published data. This dissertation provides the industry with a methodology to predict the optimal GVB design and operating parameters and their importance in creating a safe working environment. It will also contribute to the body of knowledge of the effects of face ventilation air quantity changes and how they affect the gob environment and methane dilution in working areas.
    • Spatio-temporal microseismic analysis of the Woodford Shale, Canadian County, Oklahoma

      Davis, Thomas L. (Thomas Leonard), 1947-; Eppehimer, Jarred; Sava, Paul C.; Gumble, Jason; Roche, Steven L. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Microseismicity provides data that can be used to monitor hydraulic fracture stimulation programs as well as to characterize the resulting hydraulic fractures. This is especially important in low permeability gas and oil shales, where the creation of additional permeability through these fracture treatments is essential to production. However, many applications and analyses of these data are either qualitative in nature or include a large element of interpretational bias. This study looks at two microseismic analytical techniques: the radius of gyration (ROG) tensor, as described in Sayers & Le Calvez (2010), and the methods described in Shapiro (2008) that relate spatio-temporal microseismic signatures to hydraulic diffusivity and ultimately hydraulic permeability. The radius of gyration tensor is used to generate a characteristic ellipsoid for any set of microseismic events, and the aspect ratio of this ellipsoid can be related to local in-situ horizontal stress ratios. These methods are applied to surface microseismic data collected for six horizontal wells drilled and completed in the Woodford Shale in Canadian County, Oklahoma. Additionally, an attempt is made to bridge the gap between these methods. Specifically, the characteristic ellipsoid generation from the radius of gyration tensor in Sayers & Le Calvez (2010) is applied to Shapiro’s workflow. Shapiro attempts to link the 3D anisotropic triggering front of seismicity, which is an ellipsoid that envelops time-scaled microseismic events, to reservoir permeability. The radius of gyration tensor will generate this ellipsoid and remove interpretational bias that would have been present otherwise. Lastly, an attempt is made at relating the signatures present in the characteristic ellipsoids to zones of natural fracture reactivation. This is done on a stage-by-stage basis. The hypothesis is that an ellipsoid with a significant tilt in its most vertical principal axis and a significant azimuthal rotation away from the maximum horizontal stress direction will be indicative of natural fracture reactivation. What defines a “significant” amount of deviation in each case is open to discussion and further study. The results of this study are mixed. Due to data and time restrictions, the radius of gyration tensor was only able to generate a rough range of approximations for maximum horizontal stress (see Section 3.3.1), and the lack of key core data prevented hydraulic permeability from being estimated. However, there were several results of this project that can be considered a success. First, the radius of gyration tensor can arguably be used as a natural fracture reactivation indicator, as detailed in Section 3.4. If a correlation can be drawn between natural fracture reactivation and production improvements, this tool can then be used as an indicator of which stages will perform better. This same radius of gyration tensor can also be leveraged in an otherwise interpretive analytical setting defined by Shapiro (2008), as mentioned above. This process is detailed in Section 3.5. This implies that once the relationship between ellipsoidal triggering fronts and hydraulic permeability is established, the results will be more consistent and hopefully more accurate. With this goal in mind, the axes scaling for the characteristic ellipsoids generated from the radius of gyration tensor comes into question. This issue is addressed in Section 3.5.1, and it is determined that the scaling recommended by Sayers & Le Calvez (2010) is most likely appropriate. Additionally, a filter was implemented based on the RT plots defined in Shapiro (2008) to create a microseismic data subset by removing data points that are not related to injected fluid and proppant placement (see Section 3.2). This subset is more appropriate for locating zones of natural fracture reactivation, at least for initial analyses. This subset is also recommended when determining horizontal stress ratios, although the original data should be included for comparison. The incorporation of various microseismic subsets such as this can be used to verify results of future studies. Cimarex Energy Co. has provided the data for this research, and the Reservoir Characterization Project at the Colorado School of Mines has provided the framework for the project.
    • Performance analysis of wireless sensor networks in geophysical sensing applications

      Camp, Tracy; Uligere Narasimhamurthy, Adithya; Wakin, Michael B.; Rittgers, Justin B. (Colorado School of Mines. Arthur Lakes Library, 2016)
      Performance is an important criteria to consider before switching from a wired network to a wireless sensing network. Performance is especially important in geophysical sensing where the quality of the sensing system is measured by the precision of the acquired signal. Can a wireless sensing network maintain the same reliability and quality metrics that a wired system provides? Our work focuses on evaluating the wireless GeoMote sensor motes that were developed by previous computer science graduate students at Mines. Specifically, we conducted a set of experiments, namely WalkAway and Linear Array experiments, to characterize the performance of the wireless motes. The motes were also equipped with the Sticking Heartbeat Aperture Resynchronization Protocol (SHARP), a time synchronization protocol developed by a previous computer science graduate student at Mines. This protocol should automatically synchronize the mote's internal clocks and reduce time synchronization errors. We also collected passive data to evaluate the response of GeoMotes to various frequency components associated with the seismic waves. With the data collected from these experiments, we evaluated the performance of the SHARP protocol and compared the performance of our GeoMote wireless system against the industry standard wired seismograph system (Geometric-Geode). Using arrival time analysis and seismic velocity calculations, we set out to answer the following question. Can our wireless sensing system (GeoMotes) perform similarly to a traditional wired system in a realistic scenario?