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1
Beaugendre, Camille. "Caractérisation des résines de Calophyllum inophyllum L. : approches déréplicatives pour la recherche de composés antimicrobiens." Thesis, Université Paris Cité, 2019. http://www.theses.fr/2019UNIP5067.
Повний текст джерела
2
Castaneda-Lopez, Luis Carlos. "Kinetic modeling of the hydrotreatment of light cycle oil/diesel." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1061.
Повний текст джерела
3
Oliynyk, Mariya. "Financial analysis and comparison between two oil gigants Exxonmobil and Chevron." Master's thesis, Vysoká škola ekonomická v Praze, 2014. http://www.nusl.cz/ntk/nusl-193246.
Повний текст джерелаАнотація:
This work provides financial analysis and comparison of two oil companies: Chevron and ExxonMobil, with bigger accent on practise rather than theory. It could be divided into two main parts: history and financial analysis itself. In the first part history of both oil giant was provided, from the beginning until nowadays. Second part was divided into chapters: single-criterion analysis and multiple-criteria comparison. In single-criterion analysis I applied horizontal and vertical analysis on balance sheet, income statements and cash flows statements of both companies. Then analysis of financial ratios was done: profitability, liquidity, debt, asset management, capital market and work productivity. Moreover, economic value added was calculated. In multiple-criteria comparison method of a simple division and prosperous (Tamari) and bankruptcy models (Z-score and Beerman) were calculated. In conclusion the main and the most significant results and comparison and comments were provided.
4
Abdullayev, Azer. "Effects of petroleum distillate on viscosity, density and surface tension of intermediate and heavy crude oils." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1951.
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5
Smolensky, Nicole Limunga. "Population enumeration and the effects of oil and gas development on dune-dwelling lizards." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2848.
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6
Ruiz, Vasquez Karla Liliana. "Effect of availability on multi-period planning of subsea oil and gas production systems." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2905.
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7
Ross, Trinette Noel. "Evaluation of bone biochemical markers and inflammatory markers in yearlings fed varying ratios of omega-6 and omega-3 polyunsaturated fatty acids." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1036.
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8
Kumar, Ajitabh. "Time-lapse seismic modeling and production data assimilation for enhanced oil recovery and CO2 sequestration." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3219.
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9
Madhavan, Rajiv. "Experimental investigation of caustic steam injection for heavy oils." [College Station, Tex. : Texas A&M University, 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-320.
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10
Alarcon, Alejandro. "The physiology of mycorrhizal Lolium multiflorum in the phytoremediation of petroleum hydrocarbon-contaminated soil." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1800.
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11
Ibeh, Chijioke Stanley. "Investigation on the effects of ultra-high pressure and temperature on the rheological properties of oil-based drilling fluids." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2569.
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12
Brightwell, David Aaron. "Essays on U.S. energy markets." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2928.
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13
Delgado-Marquez, Adolfo. "A linear fluid inertia model for improved prediction of force coefficients in grooved squeeze film dampers and grooved oil seal rings." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3190.
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14
Aquino, Froilan Ludana. "Elucidating the solid, liquid and gaseous products from batch pyrolysis of cotton-gin trash." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2425.
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15
Myint, Lay L. "Process analysis and optimization of biodiesel production from vegetable oils." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1267.
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16
Hernandez, Pete Jevon. "Response comparison of an optically stimulated luminescent dosimeter, a direct-ion storage dosimeter, and a thermoluminescence dosimeter." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2979.
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17
Groce, Julie Elizabeth. "Habitat associations of cavity-nesting owls in the Sierra Nevada." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3086.
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18
Lima, Maria Gabriela de Oliveira Lima Basto de. "Caracterização reológica e microstrutural de emulsões água em óleo para uso alimentar." Doctoral thesis, Universidade de Évora, 2014. http://hdl.handle.net/10174/13277.
Повний текст джерелаАнотація:
As emulsões inversas água/óleo são sistemas multifásicos complexos, constituídos por
uma fase líquida aquosa dispersa numa fase lipídica (contínua), e cristais de gordura
para estabilizar a fase dispersa. O mimetismo lipídico nestas emulsões advém da
estabilização através do controlo da cinética da cristalização das gorduras. A natureza e
a morfologia das fases formadas estão correlacionadas com as propriedades mecânicas
e reológicas destes sistemas.
Foram estudadas cinco emulsões inversas água/óleo com diferentes formulações, em
duas séries diferentes (2011 e 2013), utilizando diferentes técnicas experimentais, a saber:
espectrometria mecânica (ensaios reológicos), microscopia óptica (observação estática e
em escoamento torcional), instrumental (cor e textura) e avaliação sensorial.
Os ensaios reológicos incluíram ensaios em regime transitório (relaxação de tensões e
arranque de escoamento), ensaios em regime dinâmico (determinação do módulo de
distorção complexo) e ensaios em regime permanente (escoamento entre pratos
paralelos e escoamento Couette), para determinação experimental das funções materiais
das emulsões associadas a cada um dos ensaios referidos. A microstrutura e a
composição, o tamanho de gota e a distribuição de tamanhos de gota das emulsões
inversas foram analisadas e medidas por microscopia óptica e análise de imagem. A
visualização de escoamentos e da resposta a diferentes deformações foi efectuada
utilizando uma célula óptica de torção acoplada a um microscópio óptico e a uma câmara
digital para observação em tempo real das alterações de textura causadas por
deformações ou velocidades de deformação (escoamentos). Foi também efectuada
avaliação sensorial e instrumental (cor e textura) das diferentes composições das
emulsões inversas.
A interpretação dos resultados experimentais dos ensaios reológicos foi feita com base
no modelo de Palierne, considerando um modelo da emulsão inversa constituída por
uma fase lipídica contínua, modificada pela presença da rede de cristais lipídicos, e dois
tipos de inclusões da fase aquosa: inclusões “mais flexíveis” com uma interface lípidoágua
sem cristais lipídicos, e inclusões “menos flexíveis” onde a interface é modificada
pela rede de cristais lipídicos. O ajuste efectuado às funções materiais reológicas mostrou
que o modelo utilizado consegue descrever, com boa aproximação, os resultados
experimentais obtidos. A caracterização reológica da resposta da emulsão a diferentes
histórias da deformação (degrau de deformação, deformação sinusoidal, arranque de escoamento e escoamento permanente) foram complementadas com a observação em
tempo real, através de uma câmara digital, das alterações de textura ocorridas em cada
um dos ensaios referidos.
Foi feita uma avaliação sensorial das diferentes formulações de emulsões inversas
consideradas, utilizando um painel de provadores treinado. Através da análise de
componentes principais, verificou-se que a avaliação sensorial e a avaliação instrumental
são correlacionáveis, e que essas correlações podem ser analisadas em termos das
constantes materiais reológicas medidas experimentalmente; Rheological and microstructural characterization of water-and-oil food
emulsions
ABSTRACT:
The water-in-oil (w/o) food emulsions are complex multiphase systems, consisting of a
liquid aqueous phase dispersed in a liquid continuous lipid phase and fat crystals to
stabilize the dispersed phase. The mimicry of these lipid emulsions stabilization arises
by controlling the kinetics of crystallization of fat. The nature and morphology of the
phases formed are correlated with rheological and mechanical properties of these
systems.
Five water/oil emulsions with different formulations were studied on two different
series (2011 and 2013), using various experimental techniques, such as: mechanical
spectrometry (rheological tests); optical microscopy (torsional static and flow
observation); instrumental (colour and texture) and sensory evaluation.
The rheological measurements performed assays at transient regime (stress relaxation
and start flow), assays at dynamic regime (determination of the complex shear modulus)
and assays in steady state (flow between parallel plates and Couette flow), for
experimental determination of material functions associated with each of these tests. The
microstructure and composition, droplet size and droplet size distribution of w/o
emulsions were analyzed and measured by optical microscopy and image analysis. The
visualization of flow and response to different strains was performed using an optical
shear cell coupled to an optical microscope and a digital camera for real-time observation
of texture changes caused by deformation or strain rates (flows). Was also carried out
sensory and instrumental evaluation (colour and texture) of different compositions of
inverse emulsions.
The understanding of the experimental results of the rheological measurements was
established on Palierne model considering a inverse emulsion model comprising a
continuous lipid phase, modified by the presence of crystals lipid network, and two
kinds of aqueous phase enclosures: enclosure "more flexible "with a lipid-water interface
without lipid crystals, and enclosure "less flexible" where the interface is modified by the
lipid crystal network. The adjustment of rheological material functions showed that the
model used can describe the experimental results with close approach. The rheological
characterization of the emulsion response to different deformation history (strain step, sinusoidal deformation, start flow and continuous flow) were complemented with the
observation of texture changes occurring in each of the tests in real time using a digital
camera.
Was performed a sensory evaluation of inverse emulsions different formulations using
a trained taste panel. It was found by means of principal component analysis that the
sensory and instrumental evaluation are correlated, and these correlations can be
analysed in terms of rheological material constants experimentally measured.
19
GE, SIH-CHI, and 葛思齊. "Formulation and Optimization of Tamanu Oil Nanoemulsion Followed by Using Ulvan as Stablizer." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/01579990935156381072.
Повний текст джерелаАнотація:
碩士國立雲林科技大學
化學工程與材料工程系
104
Stability is one of the most important factors that must be considered in making emulsions. Nowadays, a wide variety of foods, pharmaceuticals, cosmetics, and agro- and petro-chemical products are constituted of emulsions. Nano-emulsions are a new type of emulsions with a particle size in the range between 10 and 300 nanometers. Because of their small-sized droplet, nano-emulsions exhibit transparent or translucent appearance. Moreover, nano-emulsions are not physically thermodynamic equilibrium but kinetically stable. The purpose of this study is to evaluate the possibility of ulvan extracted from Ulva lactuca as emulsion stabilizer. Nano-emulsions prepared under design conditions with or without the addition of ulvan were investigated for their stability. Cationic surfactant dihexadecyldimethyl ammonium bromide (DHDAB) and non-ionic surfactant polyethylene glycol stearate 40 (PEG-stearate 40) were independently applied to prepare O/W nano-emulsions composed with Tamanu oil and ultrapure water. Response surface analyses were employed to investigate the effects of oil content (%) and oil-to-surfactant ratio (SOR, %) on the particle size distributions. The results showed that the SOR is the most significant factor influencing the particle size of prepared nano-emulsions. Mathematical model predicted the particle size prepared by DHDAB and S-PEG40 will be respectively around 239.4 nm and 75.1 nm when the optimal conditions were applied. The actual particle sizes obtained from experiments using predicted condition were in good agreement with the model predicted values. All emulsion-gels exhibited elastic gel-like rheological properties. The storage modulus (G′) of emulsion-gel with a emulsion-to-ulvan ratio (EUR) at 1:3 were higher than those with EUR at 1:1 and 3:1, which could be attributed to the ordered spatial structure of emulsions. The emulsion-gel with EUR at 1:3 had a better elastic property than those with EUR at 1:1 and 3:1. The result also suggested that the emulsion-gel with EUR at 1:3 was relatively stable in comparison to other emulsion-gels obtained with EUR at 1:1 and 3:1.
20
Tran, Tan. "Bakken Shale Oil Production Trends." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9138.
Повний текст джерелаАнотація:
As the conventional reservoirs decrease in discovering, producing and reserving, unconventional reservoirs are more remarkable in terms of discovering, development and having more reserve. More fields have been discovered where Barnett Shale and Bakken Shale are the most recently unconventional reservoir examples.
Shale reservoirs are typically considered self-sourcing and have very low permeability ranging from 10-100 nanodarcies. Over the past few decades, numerous research projects and developments have been studied, but it seems there is still some contention and misunderstanding surrounding shale reservoirs.
One of the largest shale in the United State is the Bakken Shale play. This study will describe the primary geologic characteristics, field development history, reservoir properties,and especially production trends, over the Bakken Shale play.
Data are available for over hundred wells from different companies. Most production data come from the Production Data Application (HDPI) database and in the format of monthly production for oil, water and gas. Additional 95 well data including daily production rate, completion, Pressure Volume Temperature (PVT), pressure data are given from companies who sponsor for this research study.
This study finds that there are three Types of well production trends in the Bakken formation. Each decline curve characteristic has an important meaning to the production trend of the Bakken Shale play. In the Type I production trend, the reservoir pressure drops below bubble point pressure and gas releasingout of the solution.
With the Type II production trend, oil flows linearly from the matrix into the fracture system, either natural fracture or hydraulic fracture. Reservoir pressure is higher than the bubble point pressure during the producing time and oil flows as a single phase throughout the production period of the well.
A Type III production trend typically has scattering production data from wells with a different Type of trend. It is difficult to study this Type of behavior because of scattering data, which leads to erroneous interpretation for the analysis.
These production Types, especially Types I and II will give a new type curve matches for shale oil wells above or below the bubble point.
21
Gang, Gyoung Ok. "Lipid Metabolism in Bovine Subcutaneous Adipose Tissue of Steers Fed Supplementary Palm Oil or Soybean Oil." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11482.
Повний текст джерелаАнотація:
We hypothesized that supplementing finishing diets with palm oil would elevate Stearoyl-CoA desaturase (SCD) activity in muscle and subcutaneous (s.c.) adipose tissue, promoting adipocyte differentiation and increase monounsaturated fatty acids (MUFA) in beef, particularly oleic acid. Soybean oil supplementation was used as a negative control. Eighteen Angus steers were assigned randomly to three groups of 6 steers and fed a basal diet without additional fat, with 3% palm oil (rich in palmitic acid), or with 3% soybean oil (rich in polyunsaturated fatty acids), top dressed daily. There were no significant differences across treatment in quality grade, REA, 12th rib fat thickness, or yield grade. Palm oil tended to increase marbling score (P = 0.33). Palm oil supplementation decreased the concentration of myristic acid (P = 0.04), and tended to decrease the concentration of t10, c12 CLA (P = 0.07) and 18:3n-3 (P = 0.06) in s.c. adipose tissue while soybean supplementation increased c9, t11 CLA (P = 0.02) and 18:3n-3 (P = 0.03) in muscle. Palm oil supplementation increased both glucose and acetate incorporation into total lipids of s.c. adipose tissue (both P = 0.03). Volume of s.c. adipocytes was greater in cattle supplemented with palm oil than in soybean- supplemented cattle (P = 0.004). Enzyme activity of G-6-PDH tended to be greater in steers consuming palm oil supplement (P = 0.10).
We conclude that there was a partial interaction between palm oil supplementation and adipocyte differentiation. Palm oil supplementation increased s.c. adipocyte content without deteriorating meat quality traits and tended to increase marbling.
22
Nam, Hyungseok. "An Experimental Investigation of Microexplosion in Emulsified Vegetable-Methanol Blend." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10746.
Повний текст джерелаАнотація:
Vegetable oil is one of the most widely available renewable sources of energy that can be used to meet the world’s demands. Many vegetable oils also have the advantage of containing little to no detectable amounts of nitrogen. Recently, research studies have revealed that when two liquids with different vapor pressure values are formed into droplet-like emulsions, a micro-explosion effect can happen under specific environmental conditions. Understanding the micro-explosion phenomena can help increase the efficiency of bio-emulsion combustion as well as reduce pollution levels. Many researchers have conducted experiments to find the optimal condition that induces microexplosion effects. Microexplosion is also associated with the formation of shock waves characteristic of explosions at larger scales. However, little is known about how emulsion composition and droplet size affect the micro-explosion process.
Through this research, methanol-in-vegetable oil emulsion has been studied from the microexplosion point of view using custom made electric furnace equipment with a high speed camera system and an acoustic sensor system. The main goal of this study is to understand the effect of emulsion compositions, chamber temperatures, and droplet sizes on the characteristics of microexplosion. First, an n-hexadecane-in-water emulsion was prepared to validate the performance of the custom-made experimental apparatus using previous published data. Methanol-in-canola oil emulsions with different compositions were also prepared and used to compare the micro-explosion phenomena with water as a volatile compound. Microexplosion events of the blended fuels were captured using a high speed camera and an acoustic sensor. The wave signals generated by the microexplosion were analyzed after converting the signals using a Fast Fourier Transform coded in Matlab.
One of the major findings of this research work was that higher temperatures and higher concentrations of high vapor pressure fluids such as methanol and water in emulsions causes a high probability of microexplosion event due to the sudden expansion of the emulsified fluid. Also, the effect of size on microexplosion was evident in the greater probability of explosion. Methanol-in-canola oil emulsion with 15 % methanol with droplets size of 200 m placed in a furnace chamber heated to 980 ˚C showed optimal microexplosion behavior based on the formation of fine droplets. Also, smaller droplets produced higher frequencies, which could be used to detect microexplosion without high speed imaging. When large droplets microexploded, lower frequencies were detected in all the blends.
23
Samarasinghe, Nalin. "Development of an Algal Oil Separation Process." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11399.
Повний текст джерелаАнотація:
Microalgae surpass the lipid productivity of terrestrial plants by several folds. However, due to the high moisture content and rigidity of algal cell walls, extraction of lipids from algae is still a significant technological challenge. In this research, an attempt was made to develop an algal lipid separation process which is energy efficient and effective.
Algal related research requires a unique set of knowledge in areas of algae culturing, measuring cell concentration, harvesting, cell rupturing and lipid quantification. The first section of this thesis focuses on the state of the art as well as knowledge gained during preliminary studies.
The second section of this thesis focuses on selecting a suitable measurement technique for quantification of algal cell disruption induced by homogenization. The selected method, hemocytometry was used to measure the degree of algal cell disruption induced by homogenization. In the third section, various homogenization treatments were evaluated for determining the fraction of cells disrupted during the homogenization.
Finally, lipid extraction efficiency of homogenized algae was evaluated using different extraction solvents under different homogenization conditions.
Preliminary research concluded that using cell counting is the most suitable technique to measure the effect of high pressure homogenization on concentrated microalgae.
It was observed that higher pressure and increased number of passes increase the degree of cell disruption. Concentrated, non stressed samples show best response to homogenization.
Out of the three solvents used for solvent extraction, chloroform gave a higher extraction yield at low intensity homogenizations. However at harsher homogenization levels the advantage of chloroform was not significant.
Lipid extraction efficiency increases with increased levels of homogenization. However, a significant increase in lipid yields was not detected beyond 20 000 psi and 2 passes of homogenization treatment.
24
Duncan, Christopher Edward. "Factors Influencing the Stability and Marketability of a Novel, Phytochemical-Rich Oil from the Açai Palm Fruit (Euterpe oleracea Mart.)." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8789.
Повний текст джерелаАнотація:
The açai palm fruit has recently become the focus of numerous research
endeavors due to its extraordinary antioxidant content. However, little is known about
the fruit’s phytochemical rich oil, which is a by-product of the açai pulp. Therefore, the
aim of this study was to investigate the phytochemical content of açai oil and its relation
to oxidative stability.
A total of 206 mg/kg of chlorophylls, which included chlorophyll a as well as
four chlorophyll derivatives were tentatively identified by HPLC in crude açai oil
(CAO). Two predominant carotenoids (216 mg/kg β-carotene and 177 mg/kg lutein)
were also characterized in addition to α-tocopherol (645 mg/kg). Initial investigations
into oil stability focused upon the photooxidation of açai oil due to its significant
chlorophyll content and findings demonstrated that the increases of nonanal were
observed when phospholipids and polyphenolics were reduced. Subsequently,
investigations into the interactions between phospholipids and lipophilic antioxidants
and their contributions to the stability of açai oil were also assessed by isolating
phytochemicals and selectively reconstituting the oil. Findings demonstrated a potential relationship between phospholipids and lipophilic antioxidants, but this was not
conclusive.
Advances in the processing of the açai pulp by-product created from the
clarification process yielded a partially refined açai oil (RAO). The stability of both
RAO and CAO as a result of autoxidation were compared to other common food oils
(olive, canola, and soybean) and primary and secondary oxidation data suggested CAO
was most stable. The difference in the stability of the two açai oils was also investigated
by blending these oils and assessing oxidation. An increased stability was demonstrated
in the blended RAO, which suggested a significant antioxidant contribution from the
CAO. With such similar lipophilic compositions in CAO and RAO, it is theorized that
the driving factor behind the stability of CAO can be attributed to its water soluble
antioxidant content.
While further investigations are required to fully comprehend the interactions of
açai oil phytochemicals, these experiments provide insight into the phytochemical
content and stability of açai oil. The understanding and information obtained in these
studies is geared at increasing the marketability of açai oil as a food ingredient.
25
Powell, Jacob Joseph. "Engine performance and exhaust emissions from a diesel." 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2427.
Повний текст джерелаАнотація:
Non-road diesel engines are significant contributors to air pollution in the United States.
Recent regulations put forth by EPA and other environmental agencies have laid out
stringent guidelines for engine manufacturers and fuel producers. Recent increases in
oil prices and foreign energy dependency has led to a push to produce renewable fuels,
which will supplement current reserves. Biodiesel is a clean-burning renewable fuel,
that can be blended with petroleum diesel. It is important to understand the effect on
engine performance and exhaust emissions when using biodiesel from different
feedstocks. The objective of this research was to determine the relationship between
engine performance and emissions and cottonseed oil biodiesel used in a diesel engine
rated for 14.2 kW.
When using cottonseed oil biodiesel blends, CO, hydrocarbon, NOx, and SO2 emissions
decreased as compared to petroleum diesel. Carbon dioxide emissions had no definitive
trend in relation to cottonseed oil biodiesel blends. Carbon monoxide emissions
increased by an average 15% using B5 and by an average of 19% using B100. Hydrocarbon emissions decreased by 14% using B5 and by 26% using B100. Nitrogen
oxide emissions decreased by four percent with B5, five percent with B20, and 14% with
B100. Sulfur dioxide emissions decreased by an average of 86% using B100, and by
94% using B50 blended with ultra-low sulfur diesel. The difference between peak
output power when using biodiesel and diesel was insignificant in blends less that B40.
Peak measured power using B100 was about five percent lower than for diesel fuel.
Pure cottonseed oil biodiesel achieved and maintained a peak corrected measured power
of 13.1 kW at speeds of 2990, 2875, and 2800 rpm at loads of 41.3, 42.7, and 43.8 N-m.
Using B5 produced a peak power of 13.6 kW at 2990 rpm and 43.9 N-m and at 2800
rpm and 46.7 N-m, while using B20 produced a peak power of 13.4 kW at 2990 rpm and
43.7 N-m. Brake-specific fuel consumption at peak measured load and torque using
B100 was 1238 g/kW-h. Brake-specific fuel consumption at peak measured power and
loads using B5 and B20 were 1276 and 1155 g/kW-h.
26
Fuller, Christopher Byron. "Ecological Effects and In-situ Detection of Particulate Contaminants in Aqueous Environments." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9334.
Повний текст джерелаАнотація:
The ecological effects and mechanistic efficiency of chemical oil spill countermeasures must be evaluated prior to their ethical application during real spill response scenarios. Equally important is the ability to monitor the effectiveness of any spill response in real time, permitting informed response management. In-situ sensors are key components of such event based monitoring and continuous monitoring programs. This project investigates crude oil toxicity as a particulate suspension, suitability of in-situ instrumentation to measure crude oil suspensions, and the applicability of using acoustic backscatter to measure suspended solids and sub-surface oil droplet suspension concentrations.
The ecological effects to inter- and sub-tidal sediment dwelling organisms exposed to crude oil, both treated with a chemical dispersant and un-treated, was evaluated. Elevated toxicity, expressed as percent mortality and reduced luminescence, and oil concentrations were observed in inter-tidal sediments receiving oil only treatments compared to oil-plus-dispersant treatments. Sub-tidal sediments showed heterogeneous distribution of crude oil with elevated amphipod mortality compared to no oil controls suggesting an oil-sediment aggregation mechanism. A separate laboratory scale study found that the soluble crude oil fractions were responsible for the observed mortality in pelagic species while the more dominant oil droplet fractions were relatively non-toxic.
Subsequent studies focused on the in-situ detection of crude oil and particle suspensions in aqueous environments. The first showed that both in-situ fluorescence spectroscopy and Laser In-Situ Scattering Transmissometry (LISST) can effectively measure crude oil concentrations in aqueous environments. The applicability of the LISST implies that crude oil in an aqueous medium can be measured as a particle suspension. Acoustic backscatter (ABS) was investigated for its applicability as a surrogate measurement technology for aqueous particle suspensions. This study showed a log linear correlation between ABS and volume concentration (VC) over a variable particle size distribution. This correlation is due to the dependency of both ABS and VC to the particle size distribution. Log-linear ABS responses to oil-droplet suspension volume concentrations were also demonstrated. However, the inability to reproduce response factors suggests that more work is required to produce viable calibrations that may be used for sub-surface oil plume detection.
27
Chaudhary, Anish Singh. "Shale Oil Production Performance from a Stimulated Reservoir Volume." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-9970.
Повний текст джерелаАнотація:
The horizontal well with multiple transverse fractures has proven to be an effective strategy for shale gas reservoir exploitation. Some operators are successfully producing shale oil using the same strategy. Due to its higher viscosity and eventual 2-phase flow conditions when the formation pressure drops below the oil bubble point pressure, shale oil is likely to be limited to lower recovery efficiency than shale gas. However, the recently discovered Eagle Ford shale formations is significantly over pressured, and initial formation pressure is well above the bubble point pressure in the oil window. This, coupled with successful hydraulic fracturing methodologies, is leading to commercial wells. This study evaluates the recovery potential for oil produced both above and below the bubble point pressure from very low permeability unconventional shale oil formations.
We explain how the Eagle Ford shale is different from other shales such as the Barnett and others. Although, Eagle Ford shale produces oil, condensate and dry gas in different areas, our study focuses in the oil window of the Eagle Ford shale. We used the logarithmically gridded locally refined gridding scheme to properly model the flow in the hydraulic fracture, the flow from the fracture to the matrix and the flow in the matrix. The steep pressure and saturation changes near the hydraulic fractures are captured using this gridding scheme. We compare the modeled production of shale oil from the very low permeability reservoir to conventional reservoir flow behavior.
We show how production behavior and recovery of oil from the low permeability shale formation is a function of the rock properties, formation fluid properties and the fracturing operations. The sensitivity studies illustrate the important parameters affecting shale oil production performance from the stimulated reservoir volume. The parameters studied in our work includes fracture spacing, fracture half-length, rock compressibility, critical gas saturation (for 2 phase flow below the bubble point of oil), flowing bottom-hole pressure, hydraulic fracture conductivity, and matrix permeability.
The sensitivity studies show that placing fractures closely, increasing the fracture half-length, making higher conductive fractures leads to higher recovery of oil. Also, the thesis stresses the need to carry out the core analysis and other reservoir studies to capture the important rock and fluid parameters like the rock permeability and the critical gas saturation.
28
Nordt, David Paul. "A Study of Strategies for Oil and Gas Auctions." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-815.
Повний текст джерелаАнотація:
Oil and gas auctions help transact billions of dollars in property sales in the US
each year. Value is lost by participants with ineffective strategies. Federal lease
auctions have been investigated from public data, but research in this narrow area
peaked in the 1980s. Private property auctions did not emerge as a transaction force
until nearly a decade later; however, today they dwarf federal lease sales in volume and
value. This is the first study to publish research on private auctions and the first to
consolidate historical lease research findings with private auction strategies.
This dissertation reviews past research, interviews industry professionals,
analyzes case histories, conducts game experiments, and synthesizes these views for
strategic application. Findings from these efforts include the following: Reducing
uncertainty increases bid values; Federal lease bid values tend to be log normal;
Aggressive bidding results in a poor portfolio performance; Increasing competition
increases bid values; Inexperience increases aggressive bidding; A significant group of
companies do not follow consistent auction strategies; Top winning bid drivers are aggressive 3P reserves and commodity prices; Top value risks are commodity prices,
capital, and operating expenses; Properties with upside value receive higher bids using
sealed-bid auctions; Auction players can bid significantly less and sustain a high win
probability; More money is left on the table in federal lease sales than private auctions;
Poor data is primary reason auctions fail to complete the transaction; Profit taking is
primary reason for selling properties though an auction; Market metrics are useful in
valuation analysis; Producing properties receiver higher bids than undeveloped
properties with same common knowledge including total proved reserves; Oral auctions
receive higher bids than sealed-bid auctions with same common knowledge;
Competition increases bid values in sealed-bid auctions; Reserve size does not increase
relative value in sealed-bids with same common knowledge other than a magnitude of
volume.
29
Yang, Daegil. "Heavy Oil Upgrading from Electron Beam (E-Beam) Irradiation." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7630.
Повний текст джерелаАнотація:
Society's growing demands for energy results in rapid increase in oil consumption and motivates us to make unconventional resources conventional resources. There are enormous amounts of heavy oil reserves in the world but the lack of cost effective technologies either for extraction, transportation, or refinery upgrading hinders the development of heavy oil reserves.
One of the critical problems with heavy oil and bitumen is that they require large amounts of thermal energy and expensive catalysts to upgrade. This thesis demonstrates that electron beam (E-Beam) heavy oil upgrading, which uses unique features of E-Beam irradiation, may be used to improve conventional heavy oil upgrading. E-Beam processing lowers the thermal energy requirements and could sharply reduce the investment in catalysts. The design of the facilities can be simpler and will contribute to lowering the costs of transporting and processing heavy oil and bitumen.
E-Beam technology uses the high kinetic energy of fast electrons, which not only transfer their energy but also interact with hydrocarbons to break the heavy molecules with lower thermal energy.
In this work, we conducted three major stages to evaluate the applicability of E-Beam for heavy oil upgrading. First, we conducted laboratory experiments to investigate the effects of E-Beam on hydrocarbons. To do so, we used a Van de Graff accelerator, which generates the high kinetic energy of electrons, and a laboratory scale apparatus to investigate extensively how radiation effects hydrocarbons. Second, we studied the energy transfer mechanism of E-Beam upgrading to optimize the process. Third, we conducted a preliminary economic analysis based on energy consumption and compared the economics of E-Beam upgrading with conventional upgrading.
The results of our study are very encouraging. From the experiments we found that E-Beam effect on hydrocarbon is significant. We used less thermal energy for distillation of n-hexadecane (n-C16) and naphtha with E-Beam. The results of experiments with asphaltene indicate that E-Beam enhances the decomposition of heavy hydrocarbon molecules and improves the quality of upgraded hydrocarbon. From the study of energy transfer mechanism, we estimated heat loss, fluid movement, and radiation energy distribution during the reaction. The results of our economic evaluation show that E-Beam upgrading appears to be economically feasible in petroleum industry applications.
These results indicate significant potential for the application of E-Beam technology throughout the petroleum industry, particularly near production facilities, transportation pipelines, and refining industry.
30
Tien, Chih-Ming. "Quantifying the Uncertainty in Estimates of World Conventional Oil Resources." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7560.
Повний текст джерелаАнотація:
Since Hubbert proposed the "peak oil" concept to forecast ultimate recovery of crude oil for the U.S. and the world, there have been countless debates over the timing of peak world conventional oil production rate and ultimate recovery. From review of the literature, forecasts were grouped into those that are like Hubbert's with an imminent peak, and those that do not predict an imminent peak. Both groups have bases for their positions. Viewpoints from the two groups are polarized and the rhetoric is pointed and sometimes personal. A big reason for the large divide between the two groups is the failure of both to acknowledge the significant uncertainty in their estimates. Although some authors attempt to quantify uncertainty, most use deterministic methods and present single values, with no ranges. This research proposes that those that do attempt to quantify uncertainty underestimate it significantly.
The objective of this thesis is to rigorously quantify the uncertainty in estimates of ultimate world conventional oil production and time to peak rate. Two different methodologies are used. The first is a regression technique based on historical production data using Hubbert's model and the other methodology uses mathematical models. However, I conduct the analysis probabilistically, considering errors in both the data and the model, which results in likelihood probability distributions for world conventional oil production and time to peak rate. In the second method, I use a multiple-experts analysis to combine estimates from the multitude of papers presented in the literature, yielding an overall distribution of estimated world conventional oil production.
Giving due consideration to uncertainty, Hubbert-type mathematical modeling results in large uncertainty ranges that encompass both groups of forecasts (imminent peak and no imminent peak). These ranges are consistent with those from the multiple-experts analysis. In short, the industry does not have enough information at this time to say with any reliability what the ultimate world conventional oil production will be. It could peak soon, somewhere in the distant future, or somewhere in between. It would be wise to consider all of these possible outcomes in planning and making decisions regarding capital investment and formulation of energy policy.
31
Savant, Gautam Sandesh. "Characterization and Combustion Performance of Corn Oil-Based Biofuel Blends." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10896.
Повний текст джерелаАнотація:
In recent years, the development and use of biofuels have received considerable attention due to the high demand for environmentally acceptable (green) fuels. Most of the recent studies have looked at the processes of converting vegetable oils into biodiesel. It is well known vegetable oil to biodiesel conversion involves many processes including transesterification, which makes biodiesel costly and time-consuming to produce. In this study, the effects of blending high-viscosity fresh and used corn oils with low-viscosity diesel and jet fuel mixed with butanol and ethanol were studied. Several corn oil-based blends were formulated and characterized to understand the effect of composition on viscosity, fuel stability and energy content. The formulated corn oil blends were combusted in a 30 kW modified combustion chamber to determine the corresponding NOx and CO emission levels, along with CO₂ levels. Used corn oil was made by simply heating fresh corn oil for a fixed period of time (about 44 hours), and was characterized by quantifying its total polar material (TPM), iodine value, free fatty acid content, and peroxide value. The combustion experiments were conducted at a constant heat output of 68,620 kJ/hr (19 kW), to observe and study the effects of equivalence ratio, swirl number, and fuel composition on emissions. Used corn oil blends exhibited better combustion performance than fresh corn oil blends, due in part to the higher unsaturation levels in fresh corn oil. NOx emissions for used corn oil increased with swirl number. Among all the blends, the one with the higher amount of diesel (lower amount of corn oil) showed higher NOx emissions. The blend with fresh corn oil showed decreasing NOx with increasing equivalence ratio at swirl number 1.4. All blends showed generally decreasing CO trends at both swirl numbers at very lean conditions. The diesel fuel component as well as the alcohols in the blends were also important in the production of pollutants. Compared to the diesel-based blends mixed with used corn oil, butanol, and ethanol, the jet fuel-based blends showed higher NOx levels and lower CO levels at both swirl numbers.
32
Limpasurat, Akkharachai. "Artificial Geothermal Energy Potential of Steam-flooded Heavy Oil Reservoirs." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8323.
Повний текст джерелаАнотація:
This study presents an investigation of the concept of harvesting geothermal energy that
remains in heavy oil reservoirs after abandonment when steamflooding is no longer
economics. Substantial heat that has accumulated within reservoir rock and its vicinity
can be extracted by circulating water relatively colder than reservoir temperature. We
use compositional reservoir simulation coupled with a semianalytical equation of the
wellbore heat loss approximation to estimate surface heat recovery. Additionally,
sensitivity analyses provide understanding of the effect of various parameters on heat
recovery in the artificial geothermal resources. Using the current state-of-art technology,
the cumulative electrical power generated from heat recovered is about 246 MWhr
accounting for 90percent downtime.
Characteristics of heat storage within the reservoir rock were identified. The factors with
the largest impact on the energy recovery during the water injection phase are the
duration of the steamflood (which dictates the amount of heat accumulated in the
reservoir) and the original reservoir energy in place. Outlet reservoir-fluid temperatures
are used to approximate heat loss along the wellbore and estimate surface fluid
temperature using the semianalytical approaches. For the injection well with insulation,
results indicate that differences in fluid temperature between surface and bottomhole are
negligible. However, for the conventional production well, heat loss is estimated around
13 percent resulting in the average surface temperature of 72 degrees C.
Producing heat can be used in two applications: direct uses and electricity generation.
For the electricity generation application that is used in the economic consideration, the net electrical power generated by this arrival fluid temperature is approximately 3 kW
per one producing pattern using Ener-G-Rotors.
33
Ravuri, Venkata Krish Meher Surendra. "Investigation of Swirl Flows Applied to the Oil and Gas Industry." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-446.
Повний текст джерелаАнотація:
Understanding how swirl flows can be applied to processes in the oil and gas industry and how problems might hinder them, are the focus of this thesis. Three application areas were identified: wet gas metering, liquid loading in gas wells and erosion at pipe bends due to sand transport. For all three areas, Computational Fluid Dynamics (CFD) simulations were performed. Where available, experimental data were used to validate the CFD results. As a part of this project, a new test loop was conceived for the investigation of sand erosion in pipes.
The results obtained from CFD simulations of two-phase (air-water) flow through a pipe with a swirl-inducing device show that generating swirl flow leads to separation of the phases and creates distinct flow patterns within the pipe. This effect can be used in each of the three application areas of interest.
For the wet gas metering application, a chart was generated, which suggests the location of maximum liquid deposition downstream of the swirling device used in the ANUMET meter. This will allow taking pressure and phase fraction measurements (from which the liquid flow rate can be determined) where they are most representative of the flow pattern assumed for the ANUMET calculation algorithms.
For the liquid loading application, which was taken as an upscaling of the dimensions investigated for the wet gas metering application, the main focus was on the liquid hold-up. This parameter is defined as the ratio of the flowing area occupied by liquid to the total area. Results obtained with CFD simulations showed that as the water rate increases, the liquid hold-up increases, implying a more effective liquid removal. Thus, it was concluded that the introduction of a swirler can help unload liquid from a gas well, although no investigation was carried out on the persistance of the swirl motion downstream of the device.
For the third and final application, the erosion at pipe bends due to sand transport, the main focus was to check the erosion rate on the pipe wall with and without the introduction of a swirler. The erosion rate was predicted by CFD simulations. The flow that was investigated consisted of a liquid phase with solid particles suspended in it. The CFD results showed a significant reduction in erosion rate at the pipe walls when the swirler was introduced, which could translate into an extended working life for the pipe. An extensive literature review performed on this topic, complemented by the CFD simulations, showed the need for a dedicated multiphase test loop for the investigation of sand erosion in horizontal pipes and at bends. The design of a facility of this type is included in this thesis.
The results obtained with this work are very encouraging and provide a broad perspective of applications of swirl flows and CFD for the oil and gas industry.
34
Bhimani, Shreyas Mahesh. "Experimental Characterization of Canola Oil Emulsion Combustion in a Modified Furnace." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9400.
Повний текст джерелаАнотація:
Vegetable oils have been researched as alternative source of energy for many years because they have proven themselves as efficient fuel sources for diesel engines when used in the form of biodiesel, vegetable oil–diesel blends, vegetable oil-water-diesel blends and mixtures thereof. However, very few studies involving the use of emulsified low grade alcohols in straight vegetable oils, as fuels for combustion have been published. Even, the published literature involves the use of emulsified fuels only for compression ignition diesel engines. Through this project, an attempt has been made to suggest the use of alcohol-in-vegetable oil emulsions (AVOE) as an alternate fuel in stationary burners like electric utility boiler producing steam for electricity generation and more dynamic systems like diesel engines. The main goal of this study is to understand the effect of the combustion of different methanol-in-canola oil emulsions, swirl angle and equivalence ratio on the emission levels of NOx, unburned hydrocarbons (UHC), CO and CO2.
The 30 kW furnace facility available at Coal and Biomass Energy Laboratory at Texas A & M University was modified using a twin fluid atomizer, a swirler and a new liquid fuel injection system. The swirler blades were positioned at 60° and 51° angles (with respect to vertical axis) in order to achieve swirl numbers of 1.40 and 1.0, respectively. The three different fuels studied were, pure canola oil, 89-9 emulsion [9 percent methanol – in – 89 percent canola oil emulsion with 2 percent surfactant (w/w)] and 85-12.5 emulsion [12.5 percent methanol – in – 85 percent canola oil (w/w) emulsion with 2.5 percent surfactant].
All the combustion experiments were conducted for a constant heat output of 72,750 kJ/hr. One of the major findings of this research work was the influence of fuel type and swirl number on emission levels. Both the emulsions produced lower NOx, unburned (UHC) hydrocarbon and CO emissions than pure canola oil at both swirl numbers and all equivalence ratios. The emulsions also showed higher burned fraction values than pure oil and produced more CO2. Comparing the performance of only the two emulsions, it was seen that the percentage amount of methanol added to the blend had a definite positive impact on the combustion products of the fuel. The higher the percentage of methanol in the emulsions, the lesser the NOx, UHC and CO emissions. Of all the three fuels, 85-12.5 emulsion produced the least emissions. The vorticity imparted to the secondary air by the swirler also affected the emission levels. Increased vorticity at higher swirl number led to proper mixing of air and fuel which minimized emission levels at SN = 1.4. The effect of equivalence ratio on NO_x formation requires a more detailed analysis especially with regards to the mechanism which produces nitrogen oxides during the combustion of the studied fuels.
35
Olsen, Grant. "Reserves Overstatements: History, Enforcement, Identification, and Implications of New SEC Disclosure Requirements." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7907.
Повний текст джерелаАнотація:
Despite the need for accurate oil and gas reserves estimates which honor disclosure requirements of the United States Securities and Exchange Commission (SEC), a number of exploration and production companies have allegedly overstated and subsequently written down their reserves during the last 20 years. Reserves write-downs are of great interest to numerous groups involved in the reserves estimation process and outcome, including estimators, managers, investors, creditors, and regulators. Considering the magnitude and nature of some alleged overstatement cases, it appears that some of these parties may benefit from a better understanding of reserves reporting, the relative risk of overstatements, the regulatory environment and enforcement procedures, and identifying questionable reserves data. After discussing the context and importance of reserves and write-downs, there is a detailed examination of the SEC, including the agency's reserves reporting requirements, and their enforcement methods. A number of alleged overstatement and write-down "case studies" are presented, with details on the specific Federal Laws alleged to have been violated by corporations or individuals and then cited by the SEC and shareholder lawsuits. We also conclude that there may be greater write-down potential due to the updated SEC reserves reporting guidelines. A comprehensive series of systematic questions have been compiled and quick-look graphical techniques have been developed that may be used to gain insight into -and potentially raise questions about- an operator's reserves data.
36
Sunnatov, Dinmukhamed. "Experimental Study of Steam Surfactant Flood for Enhancing Heavy Oil Recovery After Waterflooding." 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7650.
Повний текст джерелаАнотація:
Steam injection with added surface active chemicals is one of general EOR
processes aimed to recover residual oil after primary production processes. It has been
demonstrated that, after waterflooding, an oil swept area can be increased by steam
surfactant flow due to the reduced steam override effect as well as reduced interfacial
tension between oil and water in the formation. To investigate the ability to improve
recovery of 20.5oAPI California heavy oil with steam surfactant injection, several
experiments with a one-dimensional model were performed.
Two experimental models with similar porous media, fluids, chemicals, as well
as injection and production conditions, were applied. The first series of experiments
were carried out in a vertical cylindrical injection cell with dimensions of 7.4 cm x 67
cm. The second part of experiment was conducted using a horizontal tube model with
dimensions of 3.5 cm x 110.5 cm. The horizontal model with a smaller diameter than the
vertical injection cell is less subject to channel formation and is therefore more applicable for the laboratory scale modeling of the one-dimensional steam injection
process.
Nonionic surfactant Triton X-100 was coinjected into the steam flow. For both
series of experimental work with vertical and horizontal injection cells, the concentration
of Triton X-100 surfactant solution used was chosen 3.0 wt%. The injection rates were
set to inject the same 0.8 pore volumes of steam for the vertical model and 1.8 pore
volumes of steam for horizontal model.
The steam was injected at superheated conditions of 200oC and pressure of 100
psig. The liquid produced from the separator was sampled periodically and treated to
determine oilcut and produced oil properties. The interfacial tension (IFT) of the
produced oil and water were measured with an IFT meter and compared to that for the
original oil. The experimental study demonstrated that the average incremental oil
recovery with steam surfactant flood is 7 % of the original oil-in-place above that with
pure steam injection.
37
Li, Weiqiang. "Improved Steam Assisted Gravity Drainage (SAGD) Performance with Solvent as Steam Additive." 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8668.
Повний текст джерелаАнотація:
Steam Assisted Gravity Drainage (SAGD) is used widely as a thermal recovery
technique in Canada to produce a very viscous bitumen formation. The main research
objectives of this simulation and experimental study are to investigate oil recovery
mechanisms under SAGD process with different injection fluids, including steam,
solvent or steam with solvent.
2D simulation studies based on typical Athabasca reservoir properties have
been performed. Results show that a successful solvent co-injection design can utilize
the advantages of solvent and steam. There is an optimal solvent type and
concentration ratio range for a particular reservoir and operating condition. Long,
continuous shale barriers located vertically above or near the wellbore delay
production performance significantly. Co-injecting a multi-component solvent can
flush out the oil in different areas with different drainage mechanisms from vaporized
and liquid components. Placing an additional injector at the top of the reservoir results
only in marginal improvement. The pure high-temperature diluent injection appears
feasible, although further technical and economic evaluation of the process is required.
A 2D scaled physical model was fabricated that represented in cross-section a
half symmetry element of a typical SAGD drainage volume in Athabasca. The
experimental results show co-injecting a solvent mixture of C7 and xylene with steam
gives better production performance than the injection of pure steam or steam with C7
at the study condition. Compared to pure steam injection runs ( Run 0 and 1),
coinjecting C7 (Run 2) with steam increases the ultimate recovery factor of oil inside
the cell from 25 percent to 29 percent and decreases the ultimate CSOR from 2.2 to 1.9 and the
ultimate CEOR from 4892 J/cm
3
to 4326 J/cm
3
; coinjecting C7 and Xylene (Run 3)
increases the ultimate recovery factor of oil from 25 percent to 34 percent, and decreases the
ultimate CSOR 2.2 to 1.6 and the ultimate CEOR from 4892 J/cm
3
to 3629 J/cm
3
.
Analyses of the experimental results indicate that partial pressure and the near
wellbore flow play important roles in production performance.
In conclusion, a successful solvent injection design can effectively improve the
production performance of SAGD. Further research on evaluating the performance of
various hydrocarbon types as steam additives is desirable and recommended.
38
Qiu, Fangda. "Experimental Study of Solvent Based Emulsion Injection to Enhance Heavy Oil Recovery." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7952.
Повний текст джерелаАнотація:
This study presents the results of nano-particle and surfactant-stabilized solvent-based emulsion core flooding studies under laboratory conditions that investigate the recovery mechanisms of chemical flooding in a heavy oil reservoir. In the study, bench tests, including the phase behavior test, rheology studies and interfacial tension measurement are performed and reported for the optimum selecting method for the nano-emulsion. Specifically, nano-emulsion systems with high viscosity have been injected into sandstone cores containing Alaska North Slope West Sak heavy oil with 16 API, which was dewatered in the laboratory condition.
The experiment results suggest that the potential application of this kind of emulsion flooding is a promising EOR (enhanced oil recovery) process for some heavy oil reservoirs in Alaska, Canada and Venezuela after primary production. Heavy oil lacks mobility under reservoir conditions and is not suitable for the application of the thermal recovery method because of environmental issues or technical problems.
Core flooding experiments were performed on cores with varied permeabilities. Comparisons between direct injection of nano-emulsion systems and nano-emulsion injections after water flooding were conducted. Oil recovery information is obtained by material balance calculation.
In this study, we try to combine the advantages of solvent, surfactant, and nano-particles together. As we know, pure miscible solvent used as an injection fluid in developing the heavy oil reservoir does have the desirable recovery feature, however it is not economical. The idea of nano-particle application in an EOR area has been recently raised by researchers who are interested in its feature-reaction catalysis-which could reduce in situ oil viscosity and generate emulsion without surfactant. Also, the nano-particle stabilized emulsions can long-distance drive oil in the reservoir, since the nano-particle size is 2-4 times smaller than the pore throat.
In conclusion, the nano-emulsion flooding can be an effective enhancement for an oil recovery method for a heavy oil reservoir which is technically sensitive to the thermal recovery method.
39
Zhang, Zhiyong. "Experimental Study of In-Situ Upgrading for Heavy Oil Using Hydrogen Donors and Catalyst under Steam Injection Condition." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9407.
Повний текст джерелаАнотація:
This research is a study of the in-situ upgrading of Jobo crude oil using steam, tetralin or decalin, and catalyst (Fe(acac)₃) at temperatures of 250 °C, 275 °C and 300 °C for 24 hours, 48 hours and 72 hours using an autoclave. Viscosity, API gravity and compositional changes were investigated. We found that tetralin and decalin alone were good solvents for heavy oil recovery. Tetralin or decalin at concentrations of 9% (weight basis) could reduce the Jobo crude oil viscosity measured at 50 °C by 44±2% and 39±3%. Steam alone had some upgrading effects. It could reduce the oil viscosity by 10% after 48 hours of contact at 300°C. Tetralin, decalin or catalyst showed some upgrading effects when used together with steam and caused 5.4±4%, 4±1% and 19±3% viscosity reduction compared with corresponding pre-upgrading mixture after 48 hours of reaction at 300°C. The combination of hydrogen donor tetralin or decalin and catalyst reduced the viscosity of the mixture the most, by 56±1% and 72±1% compared with pre-upgrading mixture. It meant that hydrogen donors and catalyst had strong synergetic effects on heavy oil upgrading. We also found that 300 °C was an effective temperature for heavy oil upgrading with obvious viscosity reduction in the presence of steam, hydrogen donors and catalyst. Reaction can be considered to have reached almost equilibrium condition after 48 hours. The GC-MS analysis of the gas component showed that light hydrocarbon gases and CO₂ were generated after reaction. The viscosity reduction from decalin use is larger than that of tetralin because decalin has more hydrogen atoms per molecule than tetralin. A mechanism of transferring H (hydrogen atom) from H₂O and hydrogen donors to heavy oil, which can lead to structure and composition changes in heavy oil, is explained. The study has demonstrated that in-situ heavy oil upgrading has great potential applications in heavy and extra heavy oil recovery.
40
Ken-Worgu, Kenneth Chukwumeka. "Petroleum Service Projects in the Gulf of Guinea." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-9749.
Повний текст джерелаАнотація:
The goal of this record of study is to examine the major facets involved in managing several petroleum service projects located in three different countries in the Gulf of Guinea simultaneously, while effectively engaging in business development activities for the Oil and Industrial Services Group (OIS). This work also furnishes adequate background on related subject matters to enable understanding of the projects presented. The petroleum services sector is the back bone of the oil and gas industry. Services companies are vital to the success of all petroleum and energy producers in the USA, the Gulf of Guinea and the world. There is a need and demand for these service companies because they play various roles such as logistics, drilling, construction, dredging, pipe laying, procurement, food supply, human resource supply, etc.
The Gulf of Guinea comprises of countries from west and central Africa. This project was limited to Nigeria, Equatorial Guinea and Cameroon. This area holds the largest petroleum reserves in Africa and plays a vital role in the global supply of petroleum. The Oil and Industrial Services Group (OIS), plans to establish herself as one of the leading petroleum service companies in this gulf. To manage this expansion, I have taken the role of Gulf of Guinea manager to apply my background as a petroleum engineer as well as my business skills to build a successful division of the company.
This work provides a record of study of the management of services, projects and contracts carried out by the OIS group in the gulf of Guinea. The following are the specific projects in the Gulf of Guinea that I participated in: Managing delivering, maintenance and marketing of offshore vessels, Offshore pipe laying project, Integrated pipeline maintenance project, Development a petroleum technical training facilities, Agbami pipe insulation project, Engineering lift project and Capital budgeting analysis for potential investments.
The details of the specific tasks of the job, including objectives, description, managerial role, nontechnical aspects, approaches, information sources, discussions and contributions are projected in the body of this literature.
41
Wang, Jianwei. "Integrated Reservoir Characterization and Simulation Studies in Stripper Oil and Gas Fields." 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2008-12-222.
Повний текст джерелаАнотація:
The demand for oil and gas is increasing yearly, whereas proven oil and gas
reserves are being depleted. The potential of stripper oil and gas fields to supplement the
national energy supply is large. In 2006, stripper wells accounted for 15% and 8% of US
oil and gas production, respectively. With increasing energy demand and current high oil
and gas prices, integrated reservoir studies, secondary and tertiary recovery methods,
and infill drilling are becoming more common as operators strive to increase recovery
from stripper oil and gas fields. The primary objective of this research was to support
optimized production of oil and gas from stripper well fields by evaluating one stripper
gas field and one stripper oil field.
For the stripper gas field, I integrated geologic and engineering data to build a
detailed reservoir characterization model of the Second White Specks (SSPK) reservoir
in Garden Plains field, Alberta, Canada. The objectives of this model were to provide
insights to controls on gas production and to validate a simulation-based method of infill
drilling assessment. SSPK was subdivided into Units A ? D using well-log facies. Units A and B are the main producing units. Unit A has better reservoir quality and
lateral continuity than Unit B. Gas production is related primarily to porosity-netthickness
product and permeability and secondarily to structural position, minor
structural features, and initial reservoir pressure.
For the stripper oil field, I evaluated the Green River formation in the Wells
Draw area of Monument Butte field, Utah, to determine interwell connectivity and to
assess optimal recovery strategies. A 3D geostatistical model was built, and geological
realizations were ranked using production history matching with streamline simulation.
Interwell connectivity was demonstrated for only major sands and it increases as well
spacing decreases. Overall connectivity is low for the 22 reservoir zones in the study
area. A water-flood-only strategy provides more oil recovery than a primary-then-waterflood
strategy over the life of the field. For new development areas, water flooding or
converting producers to injectors should start within 6 months of initial production. Infill
drilling may effectively produce unswept oil and double oil recovery. CO2 injection is
much more efficient than N2 and CH4 injection. Water-alternating-CO2 injection is
superior to continuous CO2 injection in oil recovery.
The results of this study can be used to optimize production from Garden Plains
and Monument Butte fields. Moreover, these results should be applicable to similar
stripper gas and oil field fields. Together, the two studies demonstrate the utility of
integrated reservoir studies (from geology to engineering) for improving oil and gas
recovery.
42
Cho, Young Mi. "Colon Cancer Chemoprotection through Epigenetic Effects of a Fish Oil/Pectin Diet." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11480.
Повний текст джерелаАнотація:
Accumulated genetic and epigenetic abnormalities contribute to the development of colon cancer. We have shown that a combination of fish oil (containing decosahexaenoic acid, DHA, 22:6 n-3) and pectin (fermented to butyrate by colonic microflora) is protective against colon carcinogenesis in part by regulating the expression of genes involved in apoptosis, leading to apoptosis induction.
To determine how FO/P enhances apoptosis, we measured the expression of genes involved in apoptosis. We performed a pathway analysis on differentially expressed genes identified at three times during colon tumorigenesis: initiation, aberrant crypt foci (ACF) formation, and tumor stage, and compared these results with phenotypic observations at those times. At initiation, FO/P down-regulated the expression of genes involved with cell adhesion and enhanced apoptosis compared with corn oil/cellulose (CO/C). At the ACF stage, expression of genes involved in cell cycle regulation was modulated by FO/P and proliferation was reduced in FO/P rats compared with CO/C rats. FO/P increased apoptosis and the expression of genes that promote apoptosis at the tumor endpoint compared with CO/C.
We next determined if changes in expression of genes involved in apoptosis by FO/P are associated with changes in promoter methylation of a key apoptosis regulator, Bcl-2. Genomic DNA was isolated from carcinogen-induced colon tumors and non-involved tissues. FO/P increased Bcl-2 promoter methylation in tumor tissues and colonocyte apoptosis relative to those observed with CO/C. A negative correlation between Bcl-2 DNA methylation and Bcl-2 mRNA levels was observed in the tumors.
Additionally, we examined gene specific promoter methylation of 24 apoptosis-related genes using human colon cancer cells. Cells were treated with DHA or linoleic acid (18:2 n-6), and select cultures were also treated with butyrate. The combination of DHA and butyrate led to a significant reduction in the methylation of pro-apoptotic genes and an increase in apoptosis. These data suggest that part of the mechanisms involved in the induction of apoptosis by FO/P may be through epigenetic regulation of genes involved in apoptosis throughout colon carcinogenesis.
43
Bataweel, Mohammed Abdullah. "Enhanced Oil Recovery in High Salinity High Temperature Reservoir by Chemical Flooding." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10300.
Повний текст джерелаАнотація:
Studying chemical enhanced oil recovery (EOR) in a high-temperature/high-salinity (HT/HS) reservoir will help expand the application of chemical EOR to more challenging environments. Until recently, chemical EOR was not recommended at reservoirs that contain high concentrations of divalent cations without the need to recondition the reservoir by flooding it with less saline/ less hardness brines. This strategy was found ineffective in preparing the reservoir for chemical flooding. Surfactants used for chemical flooding operating in high temperatures tend to precipitate when exposed to high concentrations of divalent cations and will partition to the oil phase at high salinities. In this study amphoteric surfactant was used to replace the traditionally used anionic surfactants. Amphoteric surfactants show higher multivalent cations tolerance with better thermal stability. A modified amphoteric surfactant with lower adsorption properties was evaluated for oil recovery. Organic alkali was used to eliminate the water softening process when preparing the chemical solution and reduce potential scale problems caused by precipitation due to incompatibility between chemical slug containing alkali and formation brine.
Using organic alkali helped in minimizing softening required when preparing an alkali-surfactant-polymer (ASP) solution using seawater. Solution prepared with organic alkali showed the least injectivity decline when compared to traditional alkalis (NaOH and Na2CO3) and sodium metaborate. Adding organic alkali helped further reduce IFT values when added to surfactant solution.
Amphoteric surfactant was found to produce low IFT values at low concentrations and can operate at high salinity / high hardness conditions. When mixed with polymer it improved the viscosity of the surfactant-polymer (SP) solution when prepared in high salinity mixing water (6% NaCl). When prepared in seawater and tested in reservoir temperature (95°C) no reduction in viscosity was found. Unlike the anionic surfactant that causes reduction in viscosity of the SP solution at reservoir temperature. This will not require increasing the polymer concentration in the chemical slug. Unlike the case when anionic surfactant was used and more polymer need to be added to compensate the reduction in viscosity.
Berea sandstone cores show lower recovery compared to dolomite cores. It was also found that Berea cores were more sensitive to polymer concentration and type and injectivity decline can be a serious issue during chemical and polymer injection. Dolomite did not show injectivity decline during chemical and polymer flooding and was not sensitive to the polymer concentration when a polymer with low molecular weight was used.
CT scan was employed to study the displacement of oil during ASP, SP, polymer and surfactant flooding. The formation and propagation oil bank was observed during these core flood experiments. ASP and SP flooding showed the highest recovery, and formation and propagation of oil bank was clearer in these experiments compared to surfactant flooding. It was found that in Berea sandstone with a permeability range of 50 to 80 md that the recovery and fluid flow was through some dominating and some smaller channels. This explained the deviation from piston-like displacement, where a sharp change in saturation in part of the flood related to the dominated channels and tapered front with late arrival when oil is recovered from the smaller channels. It was concluded that the recovery in the case of sandstone was dominated by the fluid flow and chemical propagation in the porous media not by the effectiveness of the chemical slug to lower the IFT between the displacing fluid and oil.
44
Cai, Shuzong. "Study of CO2 Mobility Control Using Cross-linked Gel Conformance Control and CO2 Viscosifiers in Heterogeneous Media." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8375.
Повний текст джерелаАнотація:
CO2 has been widely used as a displacement fluid in both immiscible and miscible displacement processes to obtain tertiary recovery from the field. There are several problems associated with the application of CO2 flooding, especially when there is a significant presence of heterogeneous elements, such as fractures, channels and high permeability streaks within the reservoir. With flooding, CO2 will finger through the target zone while leaving most of the residual/trapped oil untouched. As a result, early gas breakthrough has been a very common problem in CO2-related projects, reducing the overall sweep efficiency of CO2 flooding. This research aims at improving the CO2 flood efficiency using cross-linked gel conformance control and CO2 viscosifier technique. A series of coreflood experiment studies have been performed to investigate the possibility of applying CO2 mobility control techniques. Corresponding simulation works have also been carried out to predict the benefits of applying CO2 mobility control techniques in the field.
In the laboratory study, the CO2 coreflood system was integrated with the CT (Computed Tomography)-scanner and obtained real-time coreflood images of the CO2 saturation distributions in the core. This system was applied to the research of both cross-linked polymer gel treatment and CO2 viscosifier study and produced images with sharp phase contrasts. For the gel conformance study, promising results were obtained by applying cross-linked gel to eliminate permeability contrast and diverting CO2 into low permeability regions to obtain incremental oil recovery; also studied were the gel strength in terms of leak-off extent with the aid of CT (Computed Tomography) images. For the CO2 viscosifier research, we tested several potential viscosifier chemicals and found out PVAc (Polyvinylacetate)/toluene combination to be the most promising. The follow-up study clearly demonstrates the superiority of viscosified CO2 over neat CO2 in terms of sweep efficiency. This research serves as a preliminary study in understanding advanced CO2 mobility control techniques and will provide insights to future studies on this topic.
45
Espinel, Diaz Arnaldo Leopoldo. "Generalized Correlations to Estimate Oil Recovery and Pore Volumes Injected in Waterflooding Projects." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8886.
Повний текст джерелаАнотація:
When estimating a waterflood performance and ultimate recovery, practitioners usually prepare a plot of log of water-oil ratio vs. cumulative production or recovery factor and extrapolate the linear section of the curve to a pre-established economic limit of water production. Following this practice, engineers take the risk of overestimating oil production and/or underestimating water production if the economic limit is optimistic. Engineers would be able to avoid that risk if they knew where the linear portion of the curve finishes. We called this linear portion the "straight-line zone" of simply SLZ.
In this research, we studied that ―straight-line zone‖ and determined its boundaries (beginning and end) numerically using mathematics rules. We developed a new procedure and empirical correlations to predict oil recovery factor at any water/oil ratio.
The approach uses the fundamental concepts of fluid displacement under Buckley-Leverett fractional flow theory, reservoir simulation, and statistical analysis from multivariate linear regression.
We used commercial spreadsheet software, the Statistical Analysis Software, a commercial numerical reservoir simulator, and Visual Basic Application software.
We determined generalized correlations to determine the beginning, end, slope, and intercept of this line as a function of rock and fluid properties, such as endpoints of relative permeability curves, connate water saturation, residual oil saturation, mobility ratio, and the Dykstra-Parsons coefficient. Characterizing the SLZ allows us to estimate the corresponding recovery factor and pore volumes injected at any water-oil ratio through the length of the SLZ .
The SLZ is always present in the plot of log of water-oil ratio vs. cumulative production or recovery factor, and its properties can be predicted. Results were correlated in terms of the Dykstra-Parsons coefficient and mobility ratio. Using our correlations, practitioners can estimate the end of the SLZ without the risk of overestimating reserves and underestimating water production. Our procedure is also a helpful tool for forecasting and diagnosing waterfloods when a detailed reservoir simulation model is not available.
46
Lowder, Austin C. "Inclusion of Blended Lipid Solutions as Functional Ingredients to Alter the Fatty Acid Profile of Beef Patties." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-2935.
Повний текст джерелаАнотація:
We hypothesized that beef patties formulated with the addition of a beef fat, plant oil and rosemary extract (antioxidant) blend would increase unsaturated fatty acid content and maintain desirable sensory attributes as compared to 10 and 20% fat control beef patties. Treatment patties were formulated by combining beef trimmings (6% fat) with a lipid blend mixture (4% or 14% addition, respectively) containing 57% beef tallow, 0.3% rosemary extract and 43% of either high oleic safflower oil (SO), olive oil (OO), or corn oil (CO) to achieve a total fat content of 10 or 20%. Treatment patties were similar to control patties for lipid oxidation at 0 and 3 d of refrigerated (2oC) storage and up to 56 d of frozen (-10oC) storage. Cooked lipid blend patties at 10 or 20% fat content were similar to or higher, respectively, than control patties for juiciness and were no different for other sensory attributes evaluated. At 10 and 20% fat levels, oleic acid (18:1) in cooked SO patties (46.1 and 50.3%, respectively) and OO patties (43.8 and 48.1%, respectively) was higher than the control (37.3 and 37.6%, respectively). Unsaturated to saturated fatty acid ratios at the 10 and 20% fat levels were higher in SO (1.37 and 1.60, respectively) and CO (1.40 and 1.48, respectively) patties than the control (0.97 and 0.94, respectively). The incorporation of nutritionally enhanced lipid blends increased unsaturated fatty acid content and maintained desirable sensory attributes of beef patties while suppressing lipid oxidation.
47
Yang, Xiaole. "The Development of Dynamic Operational Risk Assessment in Oil/Gas and Chemical Industries." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7755.
Повний текст джерелаАнотація:
In oil/gas and chemical industries, dynamics is one of the most essential characteristics
of any process. Time-dependent response is involved in most steps of both
the physical/engineering processes and the equipment performance. The conventional
Quantitative Risk Assessment (QRA) is unable to address the time dependent effect
in such dynamic processes. In this dissertation, a methodology of Dynamic Operational
Risk Assessment (DORA) is developed for operational risk analysis in oil/gas
and chemical industries. Given the assumption that the component performance state
determines the value of parameters in process dynamics equations, the DORA probabilistic
modeling integrates stochastic modeling and process dynamics modeling to
evaluate operational risk. The stochastic system-state trajectory is modeled based on
the abnormal behavior or failure of the components. For each of the possible system-state
trajectories, a process dynamics evaluation is carried out to check whether
process variables, e.g., level, flow rate, temperature, pressure, or chemical concentration,
remain in their desirable regions. Monte Carlo simulations are performed to
calculate the probability of process variable exceeding the safety boundaries. Component
testing/inspection intervals and repair time are critical parameters to define the
system-state configuration; and play an important role for evaluating the probability
of operational failure. Sensitivity analysis is suggested to assist selecting the DORA probabilistic modeling inputs. In this study, probabilistic approach to characterize
uncertainty associated with QRA is proposed to analyze data and experiment results
in order to enhance the understanding of uncertainty and improve the accuracy of
the risk estimation. Different scenarios on an oil/gas separation system were used
to demonstrate the application of DORA method, and approaches are proposed for
sensitivity and uncertainty analysis. Case study on a knockout drum in the distillation
unit of a refinery process shows that the epistemic uncertainty associated with
the risk estimation is reduced through Bayesian updating of the generic reliability
information using plant specific real time testing or reliability data. Case study on
an oil/gas separator component inspection interval optimization illustrates the cost benefit
analysis in DORA framework and how DORA probabilistic modeling can be
used as a tool for decision making. DORA not only provides a framework to evaluate
the dynamic operational risk in oil/gas and chemical industries, but also guides
the process design and optimization of the critical parameters such as component
inspection intervals.
48
Tivayanonda, Vartit. "Comparison of Single, Double, and Triple Linear Flow Models for Shale Gas/Oil Reservoirs." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11748.
Повний текст джерелаАнотація:
There have been many attempts to use mathematical method in order to characterize shale gas/oil reservoirs with multi-transverse hydraulic fractures horizontal well. Many authors have tried to come up with a suitable and practical mathematical model. To analyze the production data of a shale reservoir correctly, an understanding and choosing the proper mathematical model is required. Therefore, three models (the homogeneous linear flow model, the transient linear dual porosity model, and the fully transient linear triple porosity model) will be studied and compared to provide correct interpretation guidelines for these models.
The analytical solutions and interpretation guidelines are developed in this work to interpret the production data of shale reservoirs effectively. Verification and derivation of asymptotic and associated equations from the Laplace space for dual porosity and triple porosity models are performed in order to generate analysis equations. Theories and practical applications of the three models (the homogeneous linear flow model, the dual porosity model, and the triple porosity model) are presented. A simplified triple porosity model with practical analytical solutions is proposed in order to reduce its complexity. This research provides the interpretation guidelines with various analysis equations for different flow periods or different physical properties. From theoretical and field examples of interpretation, the possible errors are presented. Finally, the three models are compared in a production analysis with the assumption of infinite conductivity of hydraulic fractures.
49
Ryu, Keun. "Effect of Cooling Flow on the Operation of a Hot Rotor-Gas Foil Bearing System." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10391.
Повний текст джерелаАнотація:
Gas foil bearings (GFBs) operating at high temperature rely on thermal management procedures that supply needed cooling flow streams to keep the bearing and rotor from overheating. Poor thermal management not only makes systems inefficient and costly to operate but could also cause bearing seizure and premature system destruction. To date, most of thermal management strategies rely on empirically based "make-and-break" techniques which are often inefficient.
This dissertation presents comprehensive measurements of bearing temperatures and shaft dynamics conducted on a hollow rotor supported on two first generation GFBs. The hollow rotor (1.36 kg, 36.51 mm OD and 17.9 mm ID) is heated from inside to reach an outer surface temperature of 120 degrees C. Experiments are conducted with rotor speeds to 30 krpm and with forced streams of air cooling the bearings and rotor. Air pressurization in an enclosure at the rotor mid span forces cooling air through the test GFBs. The cooling effect of the forced external flows is most distinct when the rotor is hottest and operating at the highest speed. The temperature drop per unit cooling flow rate significantly decreases as the cooling flow rate increases. Further measurements at thermal steady state conditions and at constant rotor speeds show that the cooling flows do not affect the amplitude and frequency contents of the rotor motions. Other tests while the rotor decelerates from 30 krpm to rest show that the test system (rigid-mode) critical speeds and modal damping ratio remain nearly invariant for operation with increasing rotor temperatures and with increasing cooling flow rates. Computational model predictions reproduce with accuracy the test data. The work adds to the body of knowledge on GFB performance and operation and provides empirically derived guidance for successful integration of rotor-GFB systems.
50
Gu, Jingping. "Essays in Applied Macroeconomics: Asymmetric Price Adjustment, Exchange Rate and Treatment Effect." 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2929.
Повний текст джерелаАнотація:
This dissertation consists of three essays. Chapter II examines the possible
asymmetric response of gasoline prices to crude oil price changes using an error
correction model with GARCH errors. Recent papers have looked at this issue. Some of
these papers estimate a form of error correction model, but none of them accounts for
autoregressive heteroskedasticity in estimation and testing for asymmetry and none of
them takes the response of crude oil price into consideration. We find that time-varying
volatility of gasoline price disturbances is an important feature of the data, and when we
allow for asymmetric GARCH errors and investigate the system wide impulse response
function, we find evidence of asymmetric adjustment to crude oil price changes in
weekly retail gasoline prices
Chapter III discusses the relationship between fiscal deficit and exchange rate.
Economic theory predicts that fiscal deficits can significantly affect real exchange rate
movements, but existing empirical evidence reports only a weak impact of fiscal deficits
on exchange rates. Based on US dollar-based real exchange rates in G5 countries and a
flexible varying coefficient model, we show that the previously documented weak relationship between fiscal deficits and exchange rates may be the result of additive
specifications, and that the relationship is stronger if we allow fiscal deficits to impact
real exchange rates non-additively as well as nonlinearly. We find that the speed of
exchange rate adjustment toward equilibrium depends on the state of the fiscal deficit; a
fiscal contraction in the US can lead to less persistence in the deviation of exchange rates
from fundamentals, and faster mean reversion to the equilibrium.
Chapter IV proposes a kernel method to deal with the nonparametric regression
model with only discrete covariates as regressors. This new approach is based on
recently developed least squares cross-validation kernel smoothing method. It can not
only automatically smooth the irrelevant variables out of the nonparametric regression
model, but also avoid the problem of loss of efficiency related to the traditional
nonparametric frequency-based method and the problem of misspecification based on
parametric model.