• Reservoir simulations integrated with geomechanics for West Sak Reservoir

      Chauhan, Nitesh; Khataniar, Santanu; Dandekar, Abhijit; Patil, Shirish (2014-07)
      Geomechanics is the study of the mechanical behavior of geologic formations. Geomechanics plays an important role in the life of a well. Without a proper understanding of the geomechanics of a reservoir, the projects associated with it may run into problems related to drilling, completion, and production. Geomechanics is important for issues such as wellbore integrity, sand production, and recovery in heavy oil reservoirs. While studying geomechanics, proper weight is given to mechanical properties such as effective mean stress, volumetric strain, etc., and the changes that these properties cause in other properties such as porosity, permeability, and yield state. The importance of analyzing geomechanics increases for complex reservoirs or reservoirs with heavy oil. This project is a case study of the West Sak reservoir in the North Slope of Alaska. Waterflooding has been implemented as enhanced oil recovery method in the reservoir. In this study, a reservoir model is built to understand the behavior and importance of geomechanics for the reservoir. First, a fluid model is built. After that, reservoir simulation is carried out by building two cases: one coupled with geomechanics and one without geomechanics. Coupling geomechanics to simulations led to the consideration of many important mechanical properties such as stress, strain, subsidence etc. Once the importance of considering geomechanical properties is established, different injection and production pressure ranges are used to understand how pressure ranges affect the geomechanical properties. The sensitivity analysis defines safer pressure ranges contingent on whether the formation is yielding or not. The yielding criterion is based on Mohr's Coulomb failure criteria. In the case of waterflooding, injection pressure should be maintained at 3800 psi or lower and production at 1600 psi or higher. And if injection rates are used as the operating parameter, it should be maintained below 1000 bbls/day. It is also observed that injection pressure dominates the geomechanics of the reservoir.
    • Resilient Modulus Characterization of Alaskan Granular Base Materials

      Li, Lin; Liu, Juanyu; Zhang, Xiong (Alaska University Transportation Center, Alaska Department of Transportation and Public Facilities, 2010)
    • Resolving Alaska's Water Resources Conflicts: Proceedings

      Dwight, Linda Perry (University of Alaska, Institute of Water Resources, 1985-11)
      Limnology -- Mining -- Hydroelectric Power Development -- Hydrology and Hydraulics -- Community and Regional Water Conflicts -- Appendix: Papers presented at the 1984 Annual Meeting
    • Resource estimation and analysis for offshore placer deposit using GIS technology

      Li, Hui (2004-12)
      In this thesis, an advanced GIS system is developed to manage, analyze and distribute Alaskan near-shore marine mineral deposition data. The developed GIS system is applied in a case study of the marine gold deposits in the offshore area of Nome, Alaska. The data collected during the previous phases of the research project are compiled using several computer application softwares such as ArcGIS8.3, Microsoft Access 2000 and others. Two improved relational geodatabases are created, in which various maps integrated with digital data sets are stored. The first database is known as the 'Integrated Geodatabase', which stores all the relative data collected in the Nome area, such as borehole data, bedrock geology, surficial geology, and geochemical data. database, a 'Regularized 2.5D Geodatabase', is generated based on the Geodatabase to store the layered orebody parameter for each regularized cell. The other Integrated With these GIS geodatabases, many important applications of data management and analysis, such as information query, data visualization, geostatistical analysis, gold distribution analysis, sediment distribution analysis, and resources estimation, are carried out readily for better understanding of Nome offshore mineral resources. Based on the enhanced GIS structure, a GIS-based website is developed using ArcIMS. Users can integrate local data sources with Internet data sources for display, query, and analysis in an easy-to-use web browser.
    • Resource estimation for platinum at Goodnews Bay, Alaska

      Tenorio, Victor Octavio (2006-08)
      Ore grade estimation is one of the most difficult problems when mining offshore deposits. In this research, a platinum deposit near Goodnews Bay, South-West of Alaska, was estimated with emerging techniques such as conditional simulation and support vector machines (SVM). Results of the estimation are presented and compared with a traditional estimation technique, such as the Inverse Distance Squared method. The area was divided in three clusters, based on the K-means method and geographical features. Also, Genetic Algorithm was used for appropriate data division. SVM parameters were optimized prior to the ore grade calculations. All estimations produced similar results for various cut-off grades, being the highest tonnages of platinum between 400 and 200 mg/m3. Reliability for conditional simulation was measured selecting blocks over 90% of probability for each cut-off value. SVM performance was evaluated using the Mean Square Error (MSE), the Mean Absolute Error (MAE) and the Correlation Coefficient Squared (R2). Using Pearson's correlation coefficient, SVM results presented a confidence of 95% in cluster 01, and 99% in clusters 02 and 03. Support vector machines seem to be an adequate tool for ore grade prediction, and it has a potential for its use in more complex geological and mining problems.
    • Response of pile-guided floats subjected to dynamic loading

      Quan, Zhili; 权致力; Chen, Gang; Metzger, Andrew; Hulsey, Leroy (2013-12)
      Pile-guided floats can be a desirable alternative to stationary berthing structures. Both floats and guide piles are subjected to time varying (dynamic) forces such as wind-generated waves and impacts from vessels. There is little design information available concerning the dynamic load environment to which the floats will be subjected. So far, the most widely acceptable method used in offshore structure design is the Kinetic Energy Method (KEM). It is a simplified method that is based on the conservation of energy. This approach is straightforward and easy to implement. However, in spite of its simplicity and straightforwardness, the method lacks accuracy. The intent of this project is to develop a rational basis for estimating the dynamic response of floating pile-guided structures, providing necessary insight into design requirements of the guide-piles. In this study, the Dynamic Analysis Method (DAM) will be used to model the dynamic responses of the system. MATLAB codes are written to help calculate the analytic and numerical values obtained from the dynamic models. For the purpose of validation, results from the two systems should be compared to a comprehensive dynamic analysis model created with the ANSYS AQWA Software.
    • The Response of Pile-Guided Floats Subjected to Dynamic Loading

      Metzger, Andrew; Quan, Zhili (Alaska University Transportation Center, Alaska Department of Transportation and Public Facilities, 2014)
    • RESULTS OF A SURVEY ON TRANSPORTATION SAFETY EQUITY IN HAWAII

      Duque de Medeiros, Flavia; Barros, Rafaela De Melo; Prevedourous, Panos (2020-07)
      Five transportation equity questions were developed for this assessment. Question 1 addressed EMS response in urban and rural areas. People with a bachelor’s degree or higher thought slightly more that rural response is worse. Rural residents believed it is worse and half of urban residents agreed. CSET minority respondents thought that rural response is slightly worse. These groups have a perception that reflects reality, according to FARS data, but the overall response to the question “Compared to urban areas, in rural areas emergency response is?” is “about the same.” Every demographic group did not support the proposal of question 2 for the government to increase gasoline taxes to collect money to invest in EMS response improvements in rural areas of Hawaii. The overall result for question 3 is that respondents were divided when it comes to converting rural roads into high standard roads in Hawaii. No demographic group had a majority response, pro, against or neutral. The response to question 4 was much clearer: all demographic groups disagreed with the proposition that the government should raise gasoline taxes to collect funds for the purpose of making rural roads safer by converting them to high standard roads. Question 5 addressed the urban-rural road funding balance: “Should more money, less money or about the same amount of money be provided to support urban road and highway improvements?” The response was mostly divided between same amount and more money, suggesting that an equal share should be allocated between urban and rural roads. Overall, the results suggest a lack of awareness of conditions on rural roads.
    • Resume of high capacity gravity separation equipment for placer gold recovery

      Mildren, Jim. (University of Alaska Mineral Industry Research Laboratory, 1975-01)
      The phenomenal and meteoric rise in gold prices in the past few years has stimulated a renewed interest in domestic gold mining and many deposits once considered valueless or at best marginal at past gold prices are now potentially mineable at a profit and will become even more attractive if new and more appropriate technology can be found and applied. There have been many new innovations in gravity separation technology since the days of the gold dredge, and most of these have been developed outside of the U. S., where placer deposits are being mined and processed for various other minerals such as rutile, illeminite, zircon, cassiterite and even diamonds. Many of these newer methods could be very profitably applied to gold recovery in many present day placer or sand and gravel operations.
    • Retrodirective phased array antenna for nanosatellites

      Long, Justin W.; Thorsen, Denise; Kegege, Obadiah; Hawkins, Joseph; Mayer, Charles (2019-12)
      This thesis presents a S-band phased array antenna for CubeSat applications. Existing state-of the-art high gain antenna systems are not well suited to the majority of CubeSats, those that fall within the 1U (10 cm x 10 cm x 10 cm) to 3U (10 cm x 10 cm x 30 cm) size ranges and in Low Earth Orbit (LEO). The system presented in this thesis is designed specifically to meet the needs of those satellites. This system is designed to fit on the 1U face (10 cm x 10 cm) of a CubeSat and requires no deployables. The use of beamforming and retrodirective algorithms reduces the pointing requirements of the antenna, easing the strict requirements that high gain antennas typically force on a CubeSat mission. Additionally, this design minimizes volume and uses low cost Commercial-off-the-Shelf (COTS) parts. This thesis discusses the theoretical background of phased array theory and retrodirective algorithms. Analysis are presented that show the characteristics and advantages of retrodirective phased antenna systems. Preliminary trade studies and design analyses show the feasibility and expected performance of a system utilizing existing COTS parts. The preliminary analysis shows that an antenna system can be achieved with ≥8.5 dBi of gain, 27dB of transmitted signal gain, 20% Power Added Efficiency (PAE) within a 1 W to 2 W power output, and an 80° effective beamwidth. Simulation results show an example antenna array that achieves 8.14 dBi of gain and an 82° effective beamwidth. Testing results on a prototype of the front-end electronics show that with minimal calibration, the beamforming and scanning error can be reduced to 5°. The power consumption and signal gain of the electronics is also verified through testing. The CubeSat Communications Platform, a CubeSat mission funded through the Air Force Research Laboratory is in Phase A design to demonstrate this antenna system, along with other experimental payloads. This thesis includes a discussion of interface control, mission requirements, operations, and a recommended experiment sequence to test and verify the antenna system on orbit.
    • Retrofit Design of Drainage Structures for Improved Fish Passage: Literature Review

      Blevins, Vanessa; Carlson, Robert F. (1988-06)
      This report reviews existing literature on issues relevant to retrofitting culverts to mitigate fish passage barriers. The analysis of this information will set the stage for future laboratory experimentation on various retrofitting techniques. The topics in this report include a review of fish swimming capabilities, hydrologic factors involved in choosing a design flow, fish passage problems resulting from conventional culvert design, and potential retrofit solutions to these problems.
    • Review and case study of electric submersible pump performance with dispersions

      Ellexson, Dexter Bryant; Awoleke, Obadare; Ning, Samson; Dandekar, Abhijit (2020-12)
      Centrifugal pump performance is very sensitive to fluid viscosity, gas fraction, and flow pattern in impeller channels. Viscous oil reduces the head and rate capacity of the pump. High gas fraction reduces the head capacity of the pump at high rates and leads to unstable surging at low rates. If the flow pattern in the impeller transitions to an elongated bubble the pump can gas-lock causing loss of production and excessive heat buildup. The complex geometry and 3-dimensional flow in a pump stage make the analysis of flow in a pump difficult without simplifying assumptions. Empirical and mechanistic models have been developed for correcting pump performance for viscosity, gas fraction, and predicting flow pattern within the impeller with reasonable accuracy. Difficulties arise when produced fluids form stable dispersions. Foams, emulsions, and solid suspensions make the determination of viscosity, gas separation efficiency, and flow pattern more difficult. Interfacial properties between phases become important in determining the bulk fluid properties, and the presence of surfactants exacerbates the interfacial effects. The objective of this project is to describe the fundamentals of electrical submersible centrifugal pumps, ESPs, and the effects that produced fluids have on their performance. These findings are then used to evaluate a case study of an ESP installed in a well with foamy and viscous crude. The ESP exhibits reduced head and rate compared to predicted viscous and gas corrections. Including interfacial effects on the fluid viscosity allow a satisfactory performance match of pump performance to be achieved. The effect of foam on pump performance can be attributed to the increased viscosity exhibited when gas behaves as a dispersed phase in a continuous oil phase rather than a separate phase in a mixture.
    • Review and experimental studies to evaluate the impact of salinity and wettability on oil recovery efficiency

      Agbalaka, Chinedu C. (2006-05)
      Oil recovery efficiency is influenced by a myriad of interacting variables such as pore geometry, wettability, rock mineralogy, brine salinity, oil composition, etc. Reservoir wettability is known to have very significant influence on pore scale displacement and hence is a strong determinant of the final residual oil saturation. Recent studies have indicated the improved oil recovery potential of low salinity brine injection. Though the reason for this reported increase is still unclear, it is speculated that it may be due to wettability changes. In this work, coreflood studies were carried out to determine the recovery benefits of low salinity waterflood over high salinity waterflood and the role of wettability in any observed recovery benefit. Two sets of coreflood experiments were conducted; the first set examined the EOR potential of low salinity floods in tertiary oil recovery processes while the second set examined the secondary oil recovery potential of low salinity floods. Changes in residual oil saturation with variation in wettability and brine salinity were monitored. All the coreflood tests consistently showed an increase in produced oil and water-wetness with decrease in brine salinity and increase in brine temperature.
    • A review of oil spill history and management on the North Slope of Alaska

      Davila, Amanda (2013-12)
      Alaska has an abundance of natural resources including oil, natural gas and coal. It is critical to minimize the occurrence of oil spills to ensure protection of Alaska's people and the environment. The objective of this project is twofold. One is to provide a quantification of the number of spills on the North Slope (NS) as well as the number of contaminated sites that are generated, describe the regulatory requirements for the Arctic zone, and discuss cleanup methods. Second is to describe the ADEC regulations as they pertain to terrestrial oil spills. The region of study begins north of Alyeska's Pump Station 4 at the Dalton Highway milepost 270, TAPS 144, north to the Beaufort Sea, encompassing all oil related operations. This review excludes spills at villages (not related to oil field operations), and releases to the atmosphere (e.g., halon, propane). Additionally, spills at formally used defense sites (FUDS) and long range radar sites are also excluded from this study. Spills that result in long term monitoring and cleanup are managed as contaminated sites. The data reveals that the majority of contaminated sites have been cleaned up with no institutional controls in place. The number of spills on the North Slope is consistent with activity. The time during the peak oil is when there are a higher number of spills. Over time, as the oil production and activity decline, so do the number of spills with a few exceptions. The decline in oil production has limited activity and growth on the NS.
    • Review of Power Sources for Alaska DOT&PF Road Weather Information Systems (RWIS): Phase I

      Wies, Richard (2014-08)
      This report documents the findings related to a review of power sources for six off-grid Road Weather Information Systems (RWIS) in Alaska. Various power sources were reviewed as a means of reliably operating the off-grid RWIS sites throughout the year. Based on information collected on current power sources and equipment used at the off-grid RWIS sites, and visits to off-grid installations in Alaska, some viable methods of reliable operation were discovered. Power sources included in the study were solar photovoltaics (PV), small wind turbines, fuel cells, and thermoelectric generators, all charging a battery bank which powers the weather sensors, cameras, and communication equipment. The results showed that while solar PV provides enough standalone power to keep the sites operational from early spring to late fall with wind supplementing this somewhat during the transition seasons, a fossil fuel based source is necessary to maintain operation through the winter. These findings suggest that a combination of power sources is required for reliable RWIS operation throughout the year and is dependent on the location of the site.
    • Risk Evaluation for Permafrost-Related Threats:Methods of Risk Estimation and Sources of Information

      Kanevskiy, Mikhail; Connor, Billy; Schnabel, Bill; Shur, Yuri; Bjella, Kevin; Trochim, Erin; Dean, Kelsey; Ellison, Ariel (2019-05)
      In our evaluation of permafrost-related threats that affect Alaska communities, we have focused on threats associated with permafrost degradation and thawing ground ice, which can result in significant thaw settlement and cause unacceptable damage to engineered structures. Our evaluation system for permafrost-related threats includes risks of general permafrost degradation and thaw settlement (general and differential). We have evaluated permafrost-related threats for 187 Alaska villages based on available information including scientific publications, maps, satellite imagery and aerial photographs, geotechnical reports, personal communication, community plans and reports, and other sources. Evaluation was based on five criteria: permafrost (PF) occurrence; PF temperature; thaw susceptibility of frozen soils (expected thaw settlement in case of permafrost degradation); massive ice occurrence; and existing PF-related problems. For each of these categories, four risk levels (ranks) were considered. The total (cumulative) risk level was based on the rating score (sum of individual ranks for all five categories). Based on the rating score, each village was assigned one of four risk levels: 0 – no permafrost; 5–8 – low risk level; 9–11 – medium risk level; 12–15 – high risk level. A vulnerability score was developed for each community allowing the identification of communities with the highest risk of damage due to thawing permafrost. Most of communities with the high-risk level (22 villages of 34) are underlain by continuous permafrost, while the low risk level is typical mainly of communities underlain by predominantly unfrozen soils/bedrocks (33 villages of 46), and no high risk levels were detected for this group of villages. Medium risk level is typical mainly of communities underlain by discontinuous and sporadic permafrost (35 villages of 47); some villages of this group are characterized by high and low risk levels (12 and 9, correspondingly). Occurrence of massive-ice bodies (mostly ice wedges) is typical exclusively of communities underlain by continuous and discontinuous permafrost (23 and 20 villages, correspondingly). We presume that at least 20 communities may have extremely ice-rich yedoma deposits with large ice wedges either within villages or in their vicinity. Permafrost conditions in Alaskan communities are very diverse, and in many cases they are extremely variable even within the same community. Detailed studies are required for more precise evaluation of potential permafrost-related threats associated with permafrost degradation and/or thawing of ground ice.
    • Robust control of geared and direct-drive robotic manipulators under parameter and model uncertainties

      Suravaram, Praveen Reddy; Bogosyan, Seta; Sonwalkar, Vikas; Aspnes, John (2005-05)
      The major contribution of this thesis is the design and evaluation of a chattering-free sliding mode controller (SMC), which is a novel application for 2 degree-of-freedom (DOF) planar robot arms exposed to load variations. The performance of the SMC is evaluated in comparison to a proportional-derivative-plus (PD+) controller, as an example of nonlinear model-based controllers, as well as classical linear controllers, such as proportional-derivative (PD) and proportional-integral-derivative (PID). The performance of all four methods has been tested via realistic and detailed simulation models developed for both geared and direct-drive type 2-DOF planar robot arms. The model used in simulations reflects the dynamics of the arm, as well as the actuator dynamics and pulse width modulation (PWM) switching of the power converters. Simulations are performed under unknown load variations for both step and sinusoidal type reference joint trajectories. The results demonstrate that the chattering-free SMC provides increased accuracy and robustness than that of the other controllers and requires no prior knowledge of the system dynamic model and the load variation that the end-effector is subjected to. The results obtained could be extended to the control of a variety of geared and direct-drive type robotic configurations.
    • Role Of Antennas And The Propagation Channel On The Performance Of An Ultra Wide Band (Uwb) Communication System

      Venkatasubramanian, Arun; Sonwalkar, Vikas (2007)
      The objectives of this dissertation are to experimentally and numerically quantify the effect of antennas and the propagation channel on the performance of an Ultra Wide Band (UWB) receiver. This work has led to the following new results: (1) the variation in the time duration of the impulse response of the oval dipole in the vertical plane is within 5% up to an angle theta = 60° off the broadside direction (theta = 90°); at larger angles a factor of six elongation in the time duration of the impulse response along the antenna axis (theta = 0°) is observed, (2) for an axial ratio of 0.5, the oval dipole has a Voltage Standing Wave Ratio (VSWR) of 2:1 (~11% reflection coefficient) in a 3.1 GHz bandwidth with a lower cut off frequency of 2.8 GHz; for an axial ratio of 2.0 this scales to 0.5 GHz bandwidth with a lower cut off frequency of 1.75 GHz, (3) a new theoretical model has been developed for UWB pulse propagation over the ground which takes into account the geometrical properties of the propagation channel (such as the heights of the transmitter (h1) and the receiver (h2) over the ground) and the nature of the radiated UWB pulse (such as pulse duration (taup) and cycle time (tauc)), (4) an improvement in bit error rate by up to a factor of 100 can be achieved for a matched filter receiver by careful orientation of the transmitting and the receiving oval dipole antennas used in the measurements presented in this dissertation.
    • The role of tundra vegetation in the Arctic water cycle

      Clark, Jason A.; Tape, Ken; Schnabel, William; Euskirchen, Eugénie; Ruess, Roger (2019-12)
      Vegetation plays many roles in Arctic ecosystems, and the role of vegetation in linking the terrestrial system to the atmosphere through evapotranspiration is likely important. Through the acquisition and use of water, vegetation cycles water back to the atmosphere and modifies the local environment. Evapotranspiration is the collective term used to describe the transfer of water from vascular plants (transpiration) and non-vascular plants and surfaces (evaporation) to the atmosphere. Evapotranspiration is known to return large portions of the annual precipitation back to the atmosphere, and it is thus a major component of the terrestrial Arctic hydrologic budget. However, the relative contributions of dominant Arctic vegetation types to total evapotranspiration is unknown. This dissertation addresses the role of vegetation in the tundra water cycle in three chapters: (1) woody shrub stem water content and storage, (2) woody shrub transpiration, and (3) partitioning ecosystem evapotranspiration into major vegetation components. In Chapter 1 I present a method to continuously monitor Arctic shrub water content. The water content of three species (Salix alaxensis, Salix pulchra, Betula nana) was measured over two years to quantify seasonal patterns of stem water content. I found that spring uptake of snowmelt water and stem water storage was minimal relative to the precipitation and evapotranspiration water fluxes. In Chapter 2, I focused on water fluxes by measuring shrub transpiration at two contrasting sites in the arctic tundra of northern Alaska to provide a fundamental understanding of water and energy fluxes. The two sites contrasted moist acidic shrub tundra with a riparian tall shrub community having greater shrub density and biomass. The much greater total shrub transpiration at the riparian site reflected the 12-fold difference in leaf area between the sites. I developed a statistical model using vapor pressure deficit, net radiation, and leaf area, which explained >80% of the variation in hourly shrub transpiration. Transpiration was approximately 10% of summer evapotranspiration in the tundra shrub community and a possible majority of summer evapotranspiration in the riparian shrub community. At the tundra shrub site, the other plant species in that watershed apparently accounted for a much larger proportion of evapotranspiration than the measured shrubs. In Chapter 3, I therefore measured partitioned evapotranspiration from dominant vegetation types in a small Arctic watershed. I used weighing micro-lysimeters to isolate evapotranspiration contributions from moss, sedge tussocks, and mixed vascular plant assemblages. I found that mosses and sedge tussocks are the major constituents of overall evapotranspiration, with the mixed vascular plants making up a minor component. The potential shrub transpiration contribution to overall evapotranspiration covers a huge range and depends on leaf area. Predicted increases in shrub abundance and biomass due to climate change are likely to alter components of the Arctic hydrologic budget. The thermal and hydraulic properties of the moss and organic layer regulate energy fluxes, permafrost stability, and future hydrologic function in the Arctic tundra. Shifts in the composition and cover of mosses and vascular plants will not only alter tundra evapotranspiration dynamics, but will also affect the significant role that mosses, their thick organic layers, and vascular plants play in the thermodynamics of Arctic soils and in the resilience of permafrost.
    • Rural Alaska Electric Power Quality

      Aspnes, J.D. (1984-03)
      Poor quality electric power has traditionally been blamed for electrical and electronic equipment malfunctions and failures in rural Alaskan communities. This report presents results of a recently completed project in which power system disturbance analyzers provide the first comprehensive power quality data from Alaskan villages. Power systems of four widely separated communities were studied for a total of 1,010 days. These results are important because of the trend in rural Alaska toward more sophisticated equipment that is sensitive to power system disturbances. These data represent a first step in developing appropriate countermeasures to protect electrical systems connected to isolated rural 60 Hz power generator facilities