Browsing by Subject "Scale"
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Item Development and application of a compositional wellbore simulator for modeling flow assurance issues and optimization of field production(2015-05) Abouie, Ali; Sepehrnoori, Kamy, 1951-Flow assurance is crucial in the oil industry since it guarantees the success and economic production of hydrocarbon fluid, especially in offshore and deep water oil fields. In fact, the ultimate goal of flow assurance is to maintain flow in the wellbore and pipelines as long as possible. One of the most common challenges in flow assurance is the buildup of solids, such as asphaltene and scale particles. These Solid particles can deposit in the wellbore, flowline, and riser and affect the wellbore performance by reducing the cross section of the pipeline, which eventually results in pipeline blockage. Hence, neglecting the importance of flow assurance problems and failure in thorough understanding of the fluid behavior in the production systems may result in plugged pipeline, production loss, flowline replacement, and early abandonments of the well. As a result, continuous evaluations are needed at the development stage and during the life of reservoirs to predict the potential, the extent, and the severity of the problem to plan for inhibition and remediation jobs. In fact, it is more preferable to prevent flow assurance problems through the designing and operating procedures rather than remediating the problems, which has higher risks of success and higher loss of revenue due to frequent well shut down. As a part of this research, we enhanced the capabilities of our in-house compositional wellbore simulator (UTWELL) to model various production and flow assurance scenarios. Initially, we developed and implemented a robust gas lift model into UTWELL to model artificial lift technique for reservoirs with low pressure. The developed model is able to model both steady state and transient flow along with blackoil and Equation-of-State compositional models. The improved version was successfully validated against a commercial simulator. Then, we applied our dynamic model to track the behavior of asphaltene during gas lift processes and evaluated the risk of asphaltene deposition. Several deposition mechanisms were incorporated to study the transportation, entrainment, and deposition of solid particles in the wellbore. The simulation results illustrated the effect of light gas injection on asphaltene deposition and well performance. Finally, a step by step algorithm is presented for coupling a geochemical package, IPhreeqc, with UTWELL. The developed model is able to model homogenous and heterogeneous, non-isothermal, non-isobaric aqueous phase reactions assuming local equilibrium or kinetic conditions. This tool was then utilized to model scale deposition in the wellbore for various scenarios. In addition, the results showed that integrating IPhreeqc has promise in terms of CPU time compared to the traditional approach of reading and writing the input and output files.Item Ecological and evolutionary analyses of range limits and biodiversity patterns(2011-12) Behrman, Kathrine Delany; Keitt, Timothy H.; Kirkpatrick, Mark, 1956-The goal of this dissertation is to further our understanding of how spatially heterogeneous landscapes may impact the formation of range boundaries that then aggregate to form large-scale biodiversity patterns. These patterns have been analyzed from many different perspectives by ecologists, evolutionary biologist, and physiologists using a variety of different theoretical, statistical, and mechanistic models. For some species, there is an obvious abrupt change in the environment causing a range boundary. Other environments change gradually, and it is unclear why species fail to adapt and expand their range. The first chapter develops a novel theoretical model of how the establishment of new mutations allows for adaptation to an environmental gradient, when there is no genetic variation for the trait that limits the range. Shallow environmental gradients favor mutations that arise nearer to the range margin, have smaller phenotypic effects, and allow for proportionately larger expansions than steep gradients. Mutations that allow for range expansion tend to have large phenotypic effects causing substantial range expansions. Spatial and temporal variation in climatic and environmental variables is important for understanding species response to climate change. The second chapter uses a mechanistic model to simulate switchgrass (Panicum virgatum L.) productivity across the central and eastern U.S. for current and future climate conditions. Florida and the Gulf Coast of Texas and Louisiana have the highest predicted current and future yields. Regions where future temperature and precipitation are anticipated to increase, larger future yields are expected. Large-scale geographic patterns of biodiversity are documented for many taxa. The mechanisms allowing for the coexistence of more of species in certain regions are poorly understood. The third chapter employs a newly developed wavelet lifting technique to extract scale-dependent patterns from irregularly spaced two-dimensional ecological data and analyzes the relationship between breeding avian richness and four energy variables. Evapotranspiration, temperature, and precipitation are significant predictors of richness at intermediate-to-large scales. Net primary production is the only significant predictor across small-to-large scales, and explains the most variation in richness (~40%) at an intermediate scale. Changes in the species-energy relationship with scale, may indicate a shift in the mechanism governing species richness.Item The limitations of structural theories of revolution : Egypt, scale, and Twitter as "History 2”(2012-12) Arnold, Timothy Jason; Winget, Megan Alicia; El-Ariss, TarekThrough a qualitative analysis of messages posted on the micro-blogging application, Twitter, and qualitative research interviews with people from Egypt and the United States who were active on Twitter during the eighteen day Egyptian Revolution in 2011, this study considers why Dr. Theda Skocpol’s theory of revolution proffered in States and Social Revolutions (1979) does not work in the case of the Egyptian Revolution. Skocpol asserts that a weakening of the state vis-à-vis a dominant class within the state or other states is a necessary precondition for revolution. By examining Twitter as a mechanism through which on-the-ground activists in Egypt were able to circumvent repressive state structures and “jump-scales” to a transnational configuration of resistance, this thesis asserts that emergent technologies complicate Skocpol’s assertion that states must be weakened politically and financially prior to the execution of a successful social revolution.Item Simulation of inorganic scales using UTCHEM reservoir simulator(2011-08) Mukhliss, Amroo Essam; Bommer, Paul Michael; Sepehrnoori, Kamy, 1951-Scale deposition, either in the formation or inside the tubing, is a serious problem that can affect the productivity of oil fields. Production sustainability depends on the successful implementation of scale management strategies prior to developing new fields. Such strategies should involve tools capable of addressing the risks of developing scales during the production stage as well as determining the outcomes of possible remediation jobs in the future. UTCHEM, a multi-compositional flow model, was used in this work to present a comprehensive study that includes both precipitation and remediation scenarios. Although there are different mechanisms prompting the deposition of mineral scales, barite and calcite were selected primarily to simulate the effect of mixing incompatible water compositions; an issue that is usually associated with seawater injection. Equilibrium state calculations were carried out using a geochemical model (EQBATCH) to verify the incompatibility of the injection water with the formation water. In this work, we show the evolution, distribution, and remediation of solids over time for several hypothetical cases. The quantity of deposits in the near-wellbore region was found to be less at a highly heterogeneous reservoir model in contrast to the amount precipitated in homogenous reservoirs. This could be critical to wells productivity in the long-run since much of the drop in reservoir pressure occurs near the wellbore. The predictive ability of UTCHEM was extended to include simulating the removal of carbonate scales using a chelating chemical. The optimization of the injected treatment can be achieved mechanically through adjusting the well spacing (during the initial stages of field development) or through adjusting the concentrations of active components in the remediation fluids. The model provides a valuable tool that helps planners to predict scaling-related issues ahead of time, and subsequently to determine the economic viability of the project. This work serves as an opportunity to re-assess this simulator and allows for further work to enhance its capabilities.Item Understanding Spatio-Temporal Variability and Associated Physical Controls of Near-Surface Soil Moisture in Different Hydro-Climates(2013-05-06) Joshi, ChampaNear-surface soil moisture is a key state variable of the hydrologic cycle and plays a significant role in the global water and energy balance by affecting several hydrological, ecological, meteorological, geomorphologic, and other natural processes in the land-atmosphere continuum. Presence of soil moisture in the root zone is vital for the crop and plant life cycle. Soil moisture distribution is highly non-linear across time and space. Various geophysical factors (e.g., soil properties, topography, vegetation, and weather/climate) and their interactions control the spatio-temporal evolution of soil moisture at various scales. Understanding these interactions is crucial for the characterization of soil moisture dynamics occurring in the vadose zone. This dissertation focuses on understanding the spatio-temporal variability of near-surface soil moisture and the associated physical control(s) across varying measurement support (point-scale and passive microwave airborne/satellite remote sensing footprint-scale), spatial extents (field-, watershed-, and regional-scale), and changing hydro-climates. Various analysis techniques (e.g., time stability, geostatistics, Empirical Orthogonal Function, and Singular Value Decomposition) have been employed to characterize near-surface soil moisture variability and the role of contributing physical control(s) across space and time. Findings of this study can be helpful in several hydrological research/applications, such as, validation/calibration and downscaling of remote sensing data products, planning and designing effective soil moisture monitoring networks and field campaigns, improving performance of soil moisture retrieval algorithm, flood/drought prediction, climate forecast modeling, and agricultural management practices.