Browsing by Subject "Scale"
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Item Competition across space : from metacommunities to social body-snatching trematodes(2019-09-13) Resetarits, Emlyn Jane; Jha, Shalene; Bolnick, Daniel; Farrior, Caroline E; Leibold, Mathew A; Mueller, Ulrich GThis dissertation is composed of two sections. The first section focuses on experimentally testing the keystone community concept using protist microcosms. I found that habitat loss can cause structural changes in how communities are assembled, even when diversity measures appear unchanged. This work has important implications for reserves management and conservation efforts. The second section is composed of three chapters on social body-snatching trematodes residing in the California horn snail. First, I investigated the tradeoff between reproduction and defense to determine if social trematode colonies increase their soldier investment in areas of high intraguild predation (IGP). I found that colonies appear to respond to IGP as predicted and do so at the site-level. Second, I conducted a reciprocal transplant experiment to determine if differences in soldier investment are due to phenotypic plasticity. Unfortunately, our results were inconclusive but provided us with valuable information on natural variation in these colonies within an estuary. Finally, I investigated how individual soldier attributes and colony composition might explain a linear competitive dominance hierarchy between six species of social body-snatching trematodes. I found that the dominance hierarchy was not explained by attributes of the colony that we measured. All totaled, there are over 20,000 trematode species, in league with the diversity of social insect groups, like ants. The trematode system is rich with opportunity to study the evolution and ecology of sociality outside of insects.Item Comprehensive modeling of flow assurance : scales, hydrates, and asphaltenes(2022-08-10) Coelho, Fernando Martins C.; Sepehrnoori, Kamy, 1951-; Ezekoye, Ofodike A.; Bahadur, Vaibhav; Lu, Yingda; Wang, YaguoIn the oil and gas industry, “flow assurance” incorporates the efforts to prevent inadvertent disruptions to the hydrocarbon flow from the wells to processing facilities. It is a reference to the study of both organic and inorganic deposits that may hinder production. Such deposits are mainly formed by scale, hydrate, asphaltene, and wax. This dissertation enhances the modeling of flow-assurance issues within a single platform—UTWELL, a wellbore simulator developed at The University of Texas at Austin. Scales result from mineral precipitation due to changes in pressure and temperature along the water flow, inherent to any gas/oil production. This research focuses on how water evaporation and CO₂ affect scaling tendencies in an oil well. The results demonstrate that evaporation is only relevant for very a small amount of water in the system, characteristic of the early stages of production. Additionally, the model shows that gas lift can increase mineral precipitation depending on the CO₂ content from the injected gas. Hydrates are ice-like solids formed under high-pressure and low-temperature conditions that are commonly found in an oilfield. Hydrate formation can be inhibited either by dissolved ions (electrolytes) in the produced water or by deliberate injection of chemicals. This research develops a hydrate-check model to verify formation conditions along the flow. The integration with a geochemical package (PHREEQC) provides the tools to consider electrolyte inhibition, and a newly included equation of state (CPA) assesses the inhibition effect from added glycols (and alcohols). The model predicts that when gas-water ratio (GWR) exceeds 10⁵ scf/STB, water condensation reduces electrolyte inhibition significantly. On asphaltenes, this research also discusses two prediction methods: a consolidated model from Li and Firoozabadi (2010), using a simplified version of the cubic-plus-association equation of state (CPA EoS); and a newly proposed version of a solid model, based on the Peng-Robinson EoS. It is shown that, if provided with adequate onset data, the solid model can match results from the CPA model quite successfully, while requiring only half the computational time. However, the solid model cannot adjust to composition changes in the same manner as CPA. Therefore, its adoption seems more suitable for wellbore simulation than in the reservoir, where fluid mixing is widespread.Item Dancing the local : two-step and the formation of local cultures, local places, and local identities in Austin, TX(2016-04-22) Ronald, Kirsten Marie; Hoelscher, Steven D.; Meikle, Jeffrey; Davis, Janet; Hartigan, John; Mellard, Jason; Rossen, RebeccaThis dissertation uses Austin’s two-step country dance scene to examine the construction of the local in American culture. Two-step is a social dance that is central to country music culture in Texas, Oklahoma, and the Southwest. Without a central governing body, the form and social norms associated with the dance vary across dance communities, which means that dancers use two-step to both construct and express their local culture. In Austin, the local two-step scene is a conservative response to neoliberal globalization, which many dancers feel is destroying Austin’s unique identity and culture. Here, the local operates along four interrelated dimensions. As a scene, the local is constituted through the performance of traditional gender roles; as a place, it is preserved and policed via social and structural constraints; as a form of belonging, it is a whiteness that is shaped by the Mexican and Mexican-American bodies and practices that it excludes; and as a scale, it is a terrestrially bound social formation that is inextricable from the global culture it purports to resist. Many cultural theorists emphasize the progressive potential of the local. However, the inner workings of Austin’s two-step scene suggest that the local can just as easily espouse an insular, exclusive politics, even in a supposedly progressive city.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 Development of an integrated compositional wellbore-reservoir simulator for flow assurance problems(2019-05) Abouie, Ali; Sepehrnoori, Kamy, 1951-; Pope, Gary A; Delshad, Mojdeh; Chapman, Walter G; Darabi, HamedFlow assurance problems such as asphaltene and geochemical scale precipitation and deposition are among the major operational challenges encountered during oil production. The variations in thermodynamic conditions such as pressure, temperature, and/or fluid composition can result in formation and deposition of solid particles (e.g., asphaltene and scale particles) in the reservoir and wellbore. Although asphaltene and scale precipitation and deposition can occur in the reservoir and near-wellbore regions, this problem is mainly observed in the production wells. Precipitation and deposition of asphaltene and scale particles in the wellbore can cause partial or total plugging of tubing. Asphaltene and scale precipitation from the reservoir fluids can also cause formation damage problems (i.e., pore throat plugging and wettability alteration) in the reservoir and near-wellbore region. These factors affect the economics of the project by lowering the production rate and requiring remediation. Application of improved oil recovery techniques such as waterflooding and miscible gas flooding has also increased the chances of scale and asphaltene formation in the wellbore and near-wellbore region. In this dissertation, we developed an integrated compositional coupled wellbore-reservoir simulator to accurately predict the detrimental effects of asphaltene and scale deposition on production performance of the oilfields. The simulation results illustrate the time and the location at which asphaltene and scale deposition damage the efficiency and productivity of the production wells. This prediction is highly crucial to monitor the production performance of the field, to optimize the field operating condition which leads to minimum asphaltene or scale formation, and to propose the effective remediation techniques. The developed wellbore model has the flexibility to work in standalone mode or in conjunction with the reservoir simulator. To accurately model the asphaltene phase behavior as a function of pressure, temperature, and hydrocarbon fluid composition, PC-SAFT equation-of-state is implemented into a non-isothermal, multiphase, multi-component compositional wellbore simulator (UTWELL). PC-SAFT models asphaltene precipitation by performing a three-phase flash calculation to determine the formation of the second-liquid phase or asphaltene-rich phase. Flocculation and deposition models are also integrated with the thermodynamic models to mimic the dynamics of asphaltene deposition during multiphase flow in the wellbore. In addition, the computational time of the reservoir simulator (UTCOMP) with PC-SAFT EOS was improved by parallelizing the phase behavior module. To investigate the dynamics of asphaltene deposition under fluid flow condition, several mechanisms such as asphaltene precipitation, asphaltene deposition, porosity and permeability reduction, wettability alteration, and viscosity modification were included in the developed model. For mechanistic modeling of scale deposition in the wellbore, a detailed procedure is presented through which a comprehensive geochemical package, IPhreeqc, is integrated within the wellbore simulator. The integrated model has the capability to model reversible, irreversible, and ion exchange reactions under non-isothermal, non-isobaric, and local equilibrium or kinetic conditions inside the wellbore. In addition, the effects of hydrocarbon components and weak acids dissolutions in the aqueous phase are included in the integrated model to accurately predict scale deposition profile. Moreover, the developed wellbore model and the reservoir simulator were coupled to investigate the effects of key parameters such as pressure, temperature, hydrocarbon fluid composition, aqueous phase composition, breakthrough time, particle transportation, and flow dynamics on asphaltene/scale precipitation and deposition. The coupled wellbore-reservoir model can also be applied to achieve the optimum solution (e.g., operating condition, injection water composition, injection gas composition) with minimum asphaltene/scale problems in the production system. Finally, continuous chemical injection model was implemented within the wellbore simulator to investigate the effectiveness of chemical injection on prevention of asphaltene precipitation. The simulation results revealed that proper selection of the type and injection rate of solvent can minimize asphaltene deposition in the wellboreItem 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 Modeling of geochemical reactions with fluid flow simulation for scale precipitation and alkaline/surfactant/polymer flooding processes(2017-12-06) Ozen, Emre; Sepehrnoori, Kamy, 1951-Precipitation of minerals is a very prevalent and crucial challenge that occurs once there are two different water phases (types), which consist of different concentration of elements, in a reservoir with changing environmental parameters such as temperature and pressure. Most operated oil and gas fields have been facing the problem of deposition of scales around and inside the wellbore since they have not only water injection but also water production. There is a lack of investigation about scale problem because of the uncomprehensive reservoir simulator considering scale precipitation during water injection and production. In this study, an in-house three-dimensional multi-phase reservoir simulator (UTCHEM) is used to model amount of scale precipitation for several cases. In this work, we neglect the effect of hydrocarbon (eg. CH₄, CO₂, and H₂S) dissolutions during scale deposition. Kinetic reactions are coupled with the fluid flow simulator to consider efficiency of water flooding process affected by scale precipitation around the injection and production wells. Several scale deposition and remediation mechanisms are investigated to tune reaction parameters against experimental data at reservoir condition to study transportation, deposition, and remediation of scales near wells. Simulation results show that ignoring scale precipitation in modeling leads to poor prediction for productivity and injectivity of water flood or another enhanced oil recovery (EOR) processes. Simulation study considering scale precipitation totally changes the performance of water flood and production scenarios. Results reveal that the composition of injected water, pH, and temperature of injected water are important factors that control the scale deposition. Meanwhile, these factors are essential to guide the scale remediation process near the wells. We also used the UTCHEM simulator to investigate the effect of temperature on geochemistry reactions during alkaline surfactant polymer (ASP) injection. Such process efficiency that rely on geochemistry reactions are depend on temperature. We also investigate two different relative permeability models in UTCHEM. A case of alkaline/surfactant polymer core flood is established to test this purpose as well as soap generation because of reaction between alkaline and acid componentsItem 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 Stars and Galaxies(McDonald Observatory, 2006) University of Texas at Austin; McDonald ObservatoryItem Strange times : dissident temporalities and the remaking of history in contemporary fiction(2015-08) Howell, Judith Hazel; Cullingford, Elizabeth; Houser, Heather; Bennett, Chad; Kevorkian, Martin; Lesser, WayneThis dissertation argues that a cluster of contemporary novelists experiment with temporalities in order to challenge the still-dominant Enlightenment view that history moves forward in a linear progression. In directing critical attention to the temporal representation of history in recent fiction, I trace a shift in contemporary preoccupations away from the postmodern concerns about the relationship of history to language, narrativity, and knowability and toward the way that temporal adjustment revises historical thinking. I show that a number of contemporary authors eschew the conventional linkages between time and history that normally structure our engagement with the past. Rather than cut the ties between time and history, however, these texts remake them through unusual temporal frameworks. I develop this argument using three case studies, which demonstrate how a particular historiographical concept—traditionally undergirded by progressivist ideologies—changes under the influence of an unconventional representation of time. Using Monique Truong’s The Book of Salt (2003) and Alan Hollinghurst’s The Swimming-Pool Library (1988), I show how queer temporalities, which reject the compulsory rhythms that often govern heteronormative culture, reconfigure archives by considering the inclusion of intentionally falsified documentation. Two works by African American novelists—Colson Whitehead’s The Intuitionist (1999) and Kiese Laymon’s Long Division (2013)—feature a temporality I call the unified now, which envisions time as past, present, and future folded together in a single unit. This temporality allows them to remake the idea of futurity by exploring how future hopes for social improvement might be realized in the present. Finally, Don DeLillo’s Point Omega (2010) and Lydia Millet’s Oh Pure and Radiant Heart (2003) alter the concept of historical scale by considering deep time that requires us to stretch our notion of history from the Big Bang to the death of our planet. They argue that this expansion of scale is the only way to come to terms with humanity’s effect on the natural world. I contend that an exploration of these temporal reorientations is crucial to understanding the contemporary historical imagination and to discovering new ways of perceiving ourselves, defining cultural and social progress, and living responsibly.