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Investigation on Wellbore Cement Integrity During Carbon Capture and Storage (CCS) and Underground Hydrogen Storage (UHS)
No full textThe interactions between hydrogen and carbon dioxide (CO2) with wellbore cement are not fully understood, raising concerns about potential degradation and failure of cement barriers during carbon capture and storage (CCS) and underground hydrogen storage (UHS). This study offers an in-depth analysis of the geochemical, petrophysical, and geo-mechanical properties of cement before and after exposure to hydrogen and CO2. In this study, the cement samples were saturated in 30,000 ppm brine and exposed to the different gases at a pressure of 500 psi and temperature of 50 C for 30 days. In the hydrogen experiment, a notable chemical alteration within the cement matrix was observed, marked by a 50% increase in brownmillerite and a 70% decrease in ettringite. Computed tomography (CT) scans revealed both diminished and clogged pores, along with areas of denser material precipitation. Correspondingly, porosity and permeability measurements showed decreases of 2% and 40%, respectively, while compressive strength and Young's modulus experienced increases of 35% and 6%. The exposure of the cement to CO2 showed significant mineralogical changes, with calcite appearing, constituting 8.7% of the mineral composition, and a complete depletion of alite, signaling extensive carbonation. CT scans highlighted a substantial reduction in pore size and sealed fractures due to calcite precipitation, dramatically affecting porosity and permeability, which decreased by 98% and 87%, respectively. Moreover, the mechanical properties saw remarkable improvements, with compressive strength and Young's modulus increasing by 126% and 161%.
This research is a first of its kind, providing a comprehensive characterization of cement samples before and after exposure to hydrogen, and comparing the results with that of CO2 exposure at the same experimental conditions. The methodological and detailed experimental and analysis approach provided a clear understanding of the interrelationship between the petrophysical, geochemical, and geomechanical impact of exposing the fluids to cement. The findings indicate that in the absence of cyclic and confining stresses, hydrogen and CO2 will not degrade the strength of the cement but, in some cases, could offer healing of fractures and microcannulas if present. The reduction in porosity and permeability of the samples suggests that losses will be reduced when the cement is exposed to hydrogen or CO2
General Sizing Relationships for Axial Flux Motors
No full textThis dissertation presents a comprehensive study of the design, optimization, and performance analysis of axial flux motors, focusing on enhancing their performance potential using a multiphysics design approach of the motor���s shared electromagnetic, thermal, and structural geometry. Axial flux motors are known for their compact structure and high power density and are increasingly becoming an item of interest for applications such as aerospace and other traction applications.
The contemporary fractured design process substantially slows novel motor design, with each subsystem designed and optimized separately. A significant contribution of this research is the development of a set of simultaneous performance scaling relationships for axial flux motors, providing a valuable tool for designers to predict motor behavior based on key geometric and system-level parameters in the early stages of design. The resulting method can estimate equivalent finite element results within 8.8% across the range of interest in approximately 1/650th the time, with a maximum error of 16.6%. The final result validation is provided via comparison with commercially available high-performance motors as well as published results relating cooling topology with current density.
The dissertation concludes with a discussion of the potential impacts of the study on the future development of axial flux motors, highlighting the opportunities for further research. This work not only advances the state-of-the-art in axial flux motor technology but also contributes to the broader field of electric machinery by providing valuable insight into how the design of electric machines can be improved to reflect the computational tools available to modern engineers
Sensitivity Analysis and Evaluation of Enhanced Geothermal Systems (EGS): Integrating Subsurface Simulation, Economics and Case Studies
No full textGeothermal energy has the potential to become a significant contributor to the effort toward energy transition because it is environmentally benign (i.e., carbon-free), renewable, and practically inexhaustible if managed properly. Geothermal energy can be extracted from different geological formations, ranging from low-temperature ones occurring at shallow depths -- suitable for heating and cooling applications -- to high-temperature reservoirs deep at kilometer-scale depths for power generation.
This study focuses on the deep geothermal systems that are referred to as Enhanced Geothermal Systems, EGS. Energy recovery from EGS involves drilling deep injection and production wells to reach deep, generally low-permeability geologic strata, and hydraulically fracturing the high-temperature rocks while ensuring communication between injectors and producers. Cold water injected into the reservoir is heated by the hot rock with which it comes in contact and is then recovered as a high-temperature fluid (liquid and/or vapor) at the production wells. Appropriate management ensures the long-term viability of this of semi-closed loop system.
In this research, I investigated in detail the thermo-hydraulic behavior of EGS by modeling the transport of fluid and heat in the subsurface by means of numerical simulation using a scientific code. I first analyzed in detail the behavior and performance of a base case model involving a representative (realistic) EGS reservoir. I then conducted (a) a thorough sensitivity analysis by varying key reservoir properties and operational practices that control/affect the behavior of the system and its efficiency, as well as (b) a techno-economic analysis based on the results of the numerical investigation studies. With the insight gained from the base and the sensitivity analysis studies, I investigated the feasibility and performance of a geothermal system at the RELLIS campus of Texas A&M University using existing data derived from earlier oil and gas recovery operations at the site. Finally, I include in this dissertation a full field-scale analysis of a geothermal system that I performed as part of an internship project at SLB (previously known as Schlumberger), an oilfield services company.
The main finding of the study is the importance of a heat-exchange surface area in the reservoir that is sufficiently large to enable (a) a high temperature of the recovered water, (b) a large flow rate (i.e., higher injection/production rates), and (c) mitigation and minimization of the inevitable thermal decline caused by the mining of heat by the injected cold water. Water (H2O) is shown to be consistently superior to supercritical CO2 (sCO2) as the heat-exchange (working) fluid, despite some thermophysical properties that appear to make sCO2 a promising candidate. The techno-economical analysis shows that drilling is the main factor increasing the cost of EGS. Thus, significant improvements in drilling efficiency and technologies are necessary to reduce the levelized cost of energy (LCOE) of EGS and make it an attractive energy recovery option
Ira Greenbaum field notebook: GK4501-GK5000.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for GK4501-GK5000 corresponding to unique identifiers of specimens/samples examined for biological research. Specimens are primarily housed at Texas A&M University; Biodiverstiy Research and Teaching Collection
Quantitative Analysis of Strain Response Measured by Low-Frequency Distributed Acoustic Sensing During Hydraulic Fracturing
No full textThis master's thesis investigates the pivotal role of strain measurements in hydraulic fracturing operations, employing Low-Frequency Distributed Acoustic Sensing (LF-DAS) technology to monitor strain changes during treatments. A significant gap in the existing research is addressed by systematically analyzing strain decay beyond the fracture domain corridor. The thesis investigates the impact of parent-well depletion and completion design on hydraulic fracture geometry, employing a decline factor of the strain decay curve as a key analytical tool. This analysis is supported by a geomechanics model, providing a comprehensive understanding of the dataset. Furthermore, the study conducts a comprehensive analysis of Hydraulic Fracture Test Site-2 (HFTS-2), considering the maximum cumulative strain change and decline factor of the strain decay curves. The thesis outlines a well-structured workflow for processing and analyzing LF-DAS cross-well strain data
Quantifying Tradeoffs Among Water Use, Energy Use, Yield and Environmental Impact for Various Levels of Irrigation and Nitrogen Fertilization of Grain Sorghum
No full textCrop production systems are the most complex systems, which have many interlinkages among different sectors. Identifying and quantifying tradeoffs among those interlinkages is important to enhance the sustainability of crop production. This study aims to use water-energy-food (WEF) nexus approach to quantify tradeoffs among water use, energy use, food production, economic return and environmental impact to identify the optimum levels of irrigation and nitrogen (N) fertilization for grain sorghum production in the southeast region of Texas. The field experiment was conducted at the research farm of Prairie View A&M University in 2023. Four irrigation levels (rainfed and three levels of crop evapotranspiration including 75%, 100% and 125%) and four N fertilizer applications (recommended level, half recommended, double recommended and zero) were selected as treatments. Water use efficiency, yield, energy productivity, net income and carbon footprint were selected as indicators to represent interlinkages among different sectors and estimated for 16 different levels of irrigation and N fertilizer application combinations. WEF nexus index was developed using the above five selected indicators and the treatment with the highest WEF nexus index was selected as optimum combination. Among 16 treatments, in rainfed conditions and at 75% ET irrigation level, yield was low, and the cost of production was high with a negative net income. Highest yield, water use efficiency and carbon footprint were observed in the 100% ET with double recommended N fertilizer application while highest energy productivity and net income were observed at the 100% ET with half recommended N fertilizer application. Application of irrigation water at 100% of crop evapotranspiration and half recommended N fertilizer (90 kg of N/ha) resulted in the highest WEF nexus index value, which is 0.812 and was hence selected as optimum levels for grain sorghum to enhance the sustainable production. The findings of this study highlight the importance of quantifying tradeoffs among water-energy and food production and applying holistic tool such as WEF nexus index to make decisions on selecting appropriate crop management practices to ensure the sustainable use of water and energy in crop production while achieving optimum productivity
Nanoscale Functionalization of Graphene-Based and Molybdenum Disulphide Samples via Electrochemical and Thermochemical Methods
No full textOur primary objective was to try to functionalize Graphene-based and Molybdenum Disulphide samples through electrochemical and thermochemical methods. The samples that we experimented with were Graphene, Graphene Oxide, and Molybdenum Disulphide on gold substrates. We chemically functionalized Graphene Oxide with Cyanuric Chloride (2,4,6- trichloro-1,3,5-triazine), assisted by an external heater source to covalently bond the compounds (thermochemical means), which was confirmed by X-ray Photoelectron Spectroscopy (XPS) results.
In the electrochemical method, we attempted to locally functionalize Graphene and Molybdenum Disulphide (MoS2) samples fabricated on a gold substrate via tip-based Local Anodic Oxidation (LAO) using a Conductive Atomic Force Microscope, where the AFM tip is connected to the positive terminal of the source meter and sample connected to the negative terminal. The local chemical changes were analyzed by measuring and comparing scan heights before the LAO. Platinum-coated Silicon tips were used due to their hardness and local corrosion resistance to pattern the 2D materials. Analysis of results and a proposed future work on the chemical functionalization of Molybdenum Disulphide were also discussed due to its surface properties akin to Graphene samples
A Characterization of the Vertical Structure and Mixing of the Eastern Mediterranean Sea
No full textObservational data collected by THEMO (The Texas A&M - University of Haifa Eastern Mediterranean Observatory) is used to characterize the seasonal variability of the water-column to understand the vertical structure and vertical mixing of the Levantine Basin in the Eastern Mediterranean Sea. Previous studies have shown the marginal Eastern Mediterranean Sea is characterized by hypersaline waters, strong water-column stratification, and regular seasonal atmospheric patterns. THEMO is composed of two surface buoys located off the coast of Haifa, Israel: one shallow buoy (water depth of 125 m; 10 km from shore) in the coastal zone of the Levantine Basin, one deep buoy (water depth of 1430 m; 60 km from shore), and one StandAlone McLane Moored Profiler (MMP), which is deployed close to the deep buoy. These instruments and buoys provide in-situ near real-time subsurface physical oceanographic observations and atmospheric observations of the Eastern Mediterranean Sea. The objectives of this research are: 1) to characterize and identify the processes that force the seasonality of the surface mixed layer depth, 2) to quantify the mechanisms that drive the hydrographic variability of the upper (surface to 1400 m depth) water-column, and 3) to categorize the stability processes of the Eastern Mediterranean Sea upper water-column using Turner Angle (Tu). Results show that the mixed layer depth varies seasonality from 250 m in Winter to less than 85 m in non-Winter months and is correlated with relatively stronger winter wind speeds (average of 7.12 m/s (Winter) to 4 m/s (non-Winter)). The upper 100 m of the water-column also experiences warming of 2 degrees C during Winter due to enhanced downward mixing of warm surface water with cooler subsurface water. Statistical analysis using empirical orthogonal functional (EOF) analysis shows that outside Winter months, variance in the principal component time-series is most correlated with the geostrophic current direction and accounts for about 50% of the total variance of water-column temperature and salinity. Characterization of water-column stability shows stable waters (-45 degrees < Tu < 45 degrees), i.e., no overturning, are most likely to occur in the upper 200 m of the water-column, and double diffusive mixing through salt fingering occur in waters below the mixed layer depth. The depth of salt fingering and stability are similar to other areas of the deep Eastern Mediterranean Sea and mid-latitude marginal seas of the world ocean
Shock-Driven Multiphase Mixing Physics in High-Speed Flows
No full textThe Shock-Driven Multiphase Instability (SDMI) occurs when a multiphase (particle-gas) medium is instantaneously accelerated by the passage of a shockwave. It has applications in detonation-driven propulsion engines, explosive dispersal of particles, hydrometeor impacts in hypersonic flight, and astrophysics events. The SDMI involves several phenomena that occur concurrently across overlapping length and time scales, from the mesoscales (cloud-scale) to the microscale (particle-scale). At the larger scales, the problem involves turbulent mixing due to acceleration across pressure and density gradients, like the classic Richtmyer-Meshkov Instability; however, including effects of larger particle or droplet sizes results in longer equilibration times and decreased mixing. At the microscale, in the case of liquid droplets, particle-scale mixing occurs due to droplet breakup and evaporation at a high Weber number. The concurrent phenomena under these conditions are complex and poorly understood, warranting research in numerous physical systems.
Considering this, I will present the findings derived from recent experiments that quantify the multiphysics aspects of the SDMI. I will dive into the impact of the particle velocity relaxation time on hydrodynamic evolution to enhance the accuracy mixing predictions from circulation deposition models. Additionally, I will explore particle-scale mixing, encompassing droplet breakup and vaporization, in quasi-1D experiments to gain a deeper understanding of their influence on hydrodynamic mixing. Moreover, I will explore the effects of high particle evaporation rates on multiphase hydrodynamic mixing. Ultimately, this work intends to develop models that accurately predict cloud-mixing time and length scales, as well as the dynamics of particle-scale mixing
Investigating Deformation and Sediment Dispersal During Andean Mountain Building in the Western Cordillera of Southern Peru
No full textThe central Andes are the archetypal modern cordilleran margin. An assessment of the timing, style, and position of deformation and associated sediment dispersal remains incomplete, especially in the Western Cordillera and forearc. Here, much of the region is overlain by Neogene extrusive igneous products from the modern Andean arc that obscure the exposures and evidence of crustal deformation. This study exploits exposures in deeply incised canyons that provide key insights into the deformational and depositional records of the Western Cordillera and forearc in southern Peru. New U-Pb zircon geochronology, structural field mapping, aerial drone 3D modeling, sediment provenance modeling, and fault kinematic forward modeling results are integrated to constrain deformation timing and style, and sediment provenance of the forearc basin. Geochronologic results from two outcrops of thrust faults that verge toward the subduction trench, paired with outcrop interpretations and forward modeling, provide detailed accounts of fault kinematics in the forearc. One fault, termed here the Aplao thrust fault, shows evidence of at least three distinct slip events throughout a long-lived history: initial compressional deformation is constrained here to between early Cretaceous and ending prior to 45.24 Ma; syndepositional deformation between 45.24 Ma and ending between 30 and 26.67 Ma; and a final episode ending before 26.67 Ma. The other structure, termed here the Toran fault, also displays multiple phases of deformation: the structure initiated as a Jurassic normal fault related to pre-Andean extension, followed by normal fault inversion and three identified compressional slip events constrained to (1) between early-middle Jurassic and ending prior to 26.67 Ma, (2) 15.98���14.07 Ma, and (3) post14.07 Ma. Sediment provenance modeling reveals upsection unroofing of the Western Cordillera and recycling of forearc basin fill, with minimal contribution from distal sources in the Altiplano or Eastern Cordillera. Results from this investigation are integrated with published depositional and deformational age constraints to place forearc deformation into context with broader orogenic controls on Andean deformation. Protracted compression in the forearc was coincident with an Eocene���early Miocene episode of flat or shallow slab subduction. This ancient slab shallowing event also drove inboard deformation of the Eastern Cordillera. This new record of shortening and unroofing in the forearc while deformation was also ongoing in the Eastern Cordillera is evidence of widespread and distributed out-of-sequence deformation and consistent with the Andean orogen being in a protracted phase of subcritical taper. The observed thrust fault geometries are consistent with a broadly bivergent Andean cordilleran system and emphasize the role of selective reactivation and inversion of inherited structures on deformation localization. These results contribute towards a complete characterization of Andean deformation, emphasizing the need for additional investigation into the cause of this long-lived compressional deformation in the forearc, even when deformation was focused far inboard from the trench