We have developed a one-dimensional numerical computer model (simulator) to describe methane hydrate formation, decomposition, reformation, and distribution with depth below the seafloor in the marine environment. The simulator was used to model hydrate distributions at Blake Ridge (Site 997) and Hydrate Ridge (Site 1249). The numerical models for the two sites were conditioned by matching the sulfate, chlorinity, and hydrate distribution measurements. The constrained models were then used to investigate the effect of changes in seafloor temperature and sea-level on gas hydrate stability. For Blake Ridge (site 997), changes in hydrate concentration are small. Both the changes in seafloor temperature and sea-level lead to a substantial increase in gas venting at the seafloor for Hydrate Ridge (site 1249).

The injection of carbon dioxide (CO2) into saline formations for the purpose of limiting greenhouse gas emissions has been proposed as an alternative to the atmospheric venting of carbon dioxide. In the evaluation process for selecting a potential target saline formation for the disposal of carbon dioxide, flow characterisation of the disposed plume should be undertaken by reservoir simulation of the target formation. The movement of injected carbon dioxide in the saline formation is influenced by many factors including the physics of carbon dioxide at deep formation depths and pressure, physical interactions with formation rock and pore water and variations in the rock flow pathways through changes in formation heterogeneity. This thesis investigates the roles of physical interactions on the disposal of carbon dioxide and the ability to contain the injected gas through evaluation of trapping mechanisms such as dissolution of CO2 in formation water and residual gas trapping through the process of gas-water relative permeability hysteresis. Variable formation heterogeneity is evaluated for its impact on the migration of injected CO2 plume movement and the role of formation heterogeneity in impeding or accelerating the immobilisation of injected carbon dioxide. Multiple reservoir simulation studies were conducted to evaluate, initially, the role of different trapping mechanisms in immobilising the movement of injected carbon dioxide and subsequently, the role of variations in formation rock in the migration and trapping of and injected plume of carbon dioxide. The major simulation study shows that the selection process for identifying appropriate saline formations should not only consider their size and permeability but should also consider their degree of heterogeneity endemic to the formation. / A set of reservoir performance metrics were developed for the CO2 disposal projects. The metrics were applied to compare plume migration of injected CO2 (both vertically and laterally) and containment (through dissolution and residual phase trapping) in these studies. The findings demonstrate how formation heterogeneity has a significant impact on the subsurface behaviour of the carbon dioxide. Formation dip influences the rate of migration, with low formation dipping reservoirs having slower rates of vertical migration. Increasing the tortuousity of the migration flow path by either increasing the shale (non-reservoir) content or lengthening the shale baffles in the formation (corresponding to a gradual decrease in reservoir quality), can progressively inhibit the vertical flow of the plume whilst promoting its lateral flow. The increase in the tortuosity of the CO2 migration pathway delays the migration of CO2 and increases the residence time for the CO2 in the formation. Thus, formation heterogeneity impedes the onset of residual gas trapping through hysteresis effects. Ultimately less carbon dioxide is likely to collect under the seal in heterogeneous formations due to increased reservoir contact and long residence times, thereby reducing the risk of seepage to overlying formations. / Given sufficient permeability for economic injection of CO2, then low to mid net-to-gross heterogeneous saline formations with low formation dip and lengthy intra-bedded shales are desirable for selection for the geological disposal of CO2. Detailed reservoir characterisation of any potential geological disposal saline formations is required in order to accurately predict the range of outcomes in the long term flow characterisation of injected CO2 into those formations.

Seismic reflection data from a multi-channel streamer deployed offshore Korea reveal evidence of hydrateforming gases being vented into the ocean. Numerous, localised vent structures are apparent from reduced seismic reflection amplitude, high seismic velocities, and reflector pull-up. These structures penetrate upward from the base of the gas hydrate stability zone (GHSZ) and are typically several hundred metres wide, and only a few hundred metres high. Underlying zones of reduced reflection amplitude and low velocities indicate the presence of gas many kilometers below the seabed, which migrates upward through near-vertical conduits to feed the vent structures. Where the local geology and underlying plumbing indicates a high flux of gases migrating through the system, the associated vent structures show the greatest change of reflector pull-up (the greatest concentration of hydrate) to be near the seabed; where the local geology and underlying plumbing indicates a moderate flux of gases, the greatest change of reflector pullup (the greatest concentration of hydrate) is near the base of the GHSZ. The distribution of gas hydrate in the high-flux gas vent is consistent with the recent salinity-driven model developed for a rapid and continuous flow of migrating gas, while the hydrate distribution in the lower-flux vent is consistent with a liquid-dominated system. The high-flux vent shows evidence of recent activity at the seabed, and it is likely that a substantial amount of gas is passing, or has passed, through this vent structure directly into the overlying ocean.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23862号 / 工博第4949号 / 新制||工||1773(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 角 哲也, 准教授 竹門 康弘, 准教授 Kantoush Sameh / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Background: Electronic Word of Mouth (eWOM) is something that lately has gained increasing relevance and importance when it comes to consumers purchase decisions. Online reviews are considered to be the most important and reliable form of eWOM and it refers to when consumers communicate with other consumers online regarding their previous shopping experiences. In order to increase the generalizability and understanding of motives that influence consumers intention to write online reviews, authors of previous studies have suggested that future research should intend to focus on motives that influence intention to write online reviews in other contexts that are not aimed towards the service industry. Purpose: The purpose of this study is to explain how personal- and social motives influence consumers intention to write online product reviews. Methodology: For this explanatory study, a quantitative strategy with a cross-sectional research design were used in order to test the model founded on two major hypotheses. The data was gathered through a self-completed questionnaire with a sample of 222 respondents. Findings: In this study, two major hypotheses were conducted in order to explain how personal motives and social motives influence consumers intention to write online product reviews. After analysing the data that emerged from the survey, a conclusion can be drawn that the hypothesis concerning personal motives and its influence on consumers intention to write online product reviews was accepted whereas the hypothesis concerning social motives was rejected. Conclusion: In this study, it has been recommended that future studies should test the suggestions found in this study with a more diverse sample in order to increase the generalizability of the theoretical implications. Furthermore, directions for future research will also recommend testing the modified model that emerged in this paper in order to detect if there are any additions that need to be added to increase the predictability of the findings.

[pt] Anualmente, mais de 100 bilhões de metros cúbicos de gás são queimados mundialmente em flares nas instalações de petróleo e gás natural. Esse número era ainda maior a alguns anos atrás. No passado, o holofote estava sobre o petróleo e o gás natural era visto como uma fonte de energia não rentável. A preocupação mundial com o aquecimento global impulsionou as ações para redução das emissões de gases causadores do efeito estufa. A crescente mobilização dos órgãos reguladores de diversos países para imposição de restrições de queima e ventilação do gás natural vem contribuindo para a melhoria dos índices de aproveitamento do gás associado. Muito embora já tenha havido um avanço relevante, o montante de gás desperdiçado ainda precisa ser reduzido. Neste contexto, a necessidade de se quantificar corretamente os volumes desperdiçados de gás fica evidente. As ações para redução da queima ou ventilação de gás natural se baseiam fortemente em medições precisas. O reflexo disto são as constantes publicações de diretrizes regulatórias voltadas para as medições de vazão de gás dos sistemas de alívio/tocha. Apesar da medição de gás de flare não ser uma técnica nova, ela ainda é considerada desafiadora e bem diferente das demais aplicações de medição de vazão. A natureza imprevisível da queima de gás natural, associada a instalações inadequadas, torna a medição extremamente difícil e complexa. O presente trabalho traz uma visão geral da queima de gás natural, da regulação do tema no Brasil e no mundo e das características e desafios da medição de gás de flare. Adicionalmente, foram feitos estudos de incerteza sobre os volumes diários medidos nos pontos fiscais de gás de uma instalação típica, de forma a analisar a influência da incerteza da medição do gás de tocha sobre a incerteza da produção mensal de gás natural, que é a base de cálculo para as devidas participações governamentais. Também foram calculadas as diferenças obtidas entre a medição indireta (balanço volumétrico de gás) e a medição direta (medição ultrassônica) da queima de gás natural e as incertezas relacionadas à medição indireta. / [en] Annually, more than 100 billion cubic meters of gas are flared from upstream oil and gas facilities. This number was even higher a few years ago. In the past, the spotlight was on oil and natural gas was seen as a non-profitable source of energy. The worldwide concern over global warming spurred actions to reduce emissions of greenhouses effect gases, contributing to change the scenario above. The increased mobilization of regulators from many countries enforcing gas flaring and venting restrictions has contributed to the improvement of gas use. However, although some progress has been already achieved, the amount of wasted gas still needs to be reduced. In this context, the need to correctly quantify the volumes of gas flared is evident. Actions to reduce the flaring or venting of natural gas rely heavily on accurate measurements. This reflects on the rigorous flare measurement guidelines introduced by many countries to support flaring legislation. Although the flare gas measurement is not a new technique, it is still considered a challenging task and quite unique compared to other flow measurement applications. The unpredictable nature of the flaring, many times happening at inadequate facility, makes measuring it extremely difficult and complex. This work provides an overview of gas flaring, regulatory requirements in Brazil and worldwide and the characteristics and challenges of flare gas measurement. In addition, uncertainty studies were made over the daily volumes measured in the fiscal points of a typical installation, in order to analyze the influence of the uncertainty of flared gas measurement on the uncertainty of monthly gas production, which is the basis for calculating the government takes. The differences obtained between the gas flaring indirect measurement (bydifference method) and direct measurement (ultrasonic measurement) were also calculated, as well as the uncertainties related to the indirect measurement.

The issue of gas flaring and the attendant environmental effects have become a common sight in the Niger Delta. Apart from being a wastage of natural resources, it is a menace to the global existence of man. The incidences of acid rain and the disruption of economic life of the locals, basically farming and fishing, have led to consistent and irresistible agitation by the people of the Niger Delta for an end to gas flaring. The consistent release of harmful gases through gas flaring, with devastating effect on the surrounding environment of the Niger Delta region is discussed in this work. This dissertation examines why successive governments have not succeeded in their quest for a solution to gas flaring; policies and regulations are not being effectively implemented, and why despite the fact that flaring has been outlawed in Nigeria since 1st January 1984, it is still going on 24 years after. Flaring continues unabated undermining the consequences it has on the people and the effects on climate change. Interviews and case studies were used to examine the factors responsible for the non implementation of government policies and regulations, and why the consistent extension of flare-out deadline. Countries with outstanding results were examined in order to draw a baseline for the Nigeria situation. The research revealed that the Nigerian government has not enforced environmental regulations effectively because of its interests in the business of the multinationals. In addition there has been the dependence of environmental monitoring and regulatory agencies on government funding. This has drastically affected the proficiencies of the control and the insignificant penalties imposed on companies that flare gas. The need for government to play the role of an umpire rather than business partner with the multinationals is therefore of paramount importance. It is also pertinent that the regulatory and monitoring agencies be independent of government's supervision. More stringent measures, (ranging from more cost per a thousand standard cubic feet of gas flared to closure of platform(s) and/or outright withdrawal of license), should also be put in place to serve as deterrent to erring oil companies. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2009.

The issue of gas flaring and the attendant environmental effects have become a common sight in the Niger Delta. Apart from being a wastage of natural resources, it is a menace to the global existence of man. The incidences of acid rain and the disruption of economic life of the locals, basically farming and fishing, have led to consistent and irresistible agitation by the people of the Niger Delta for an end to gas flaring. The consistent release of harmful gases through gas flaring, with devastating effect on the surrounding environment of the Niger Delta region is discussed in this work. This dissertation examines why successive governments have not succeeded in their quest for a solution to gas flaring; policies and regulations are not being effectively implemented, and why despite the fact that flaring has been outlawed in Nigeria since 1st January 1984, it is still going on 24 years after. Flaring continues unabated undermining the consequences it has on the people and the effects on climate change. Interviews and case studies were used to examine the factors responsible for the non implementation of government policies and regulations, and why the consistent extension of flare-out deadline. Countries with outstanding results were examined in order to draw a baseline for the Nigeria situation. The research revealed that the Nigerian government has not enforced environmental regulations effectively because of its interests in the business of the multinationals. In addition there has been the dependence of environmental monitoring and regulatory agencies on government funding. This has drastically affected the proficiencies of the control and the insignificant penalties imposed on companies that flare gas. The need for government to play the role of an umpire rather than business partner with the multinationals is therefore of paramount importance. It is also pertinent that the regulatory and monitoring agencies be independent of government's supervision. More stringent measures, (ranging from more cost per a thousand standard cubic feet of gas flared to closure of platform(s) and/or outright withdrawal of license), should also be put in place to serve as deterrent to erring oil companies. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2009.

Currently, the plastics industry has a wide range of applications due to the possibility of a fully automated process or through increased production efficiencies. The reason for this choice of the thesis was to understand the whole issue of plastic injection molding process. The specified component is used to atach the sail, which serves to protect workers in the welding sector. A specified number of the series is 350 000. The work includes a theoretical problem of injection molding process, selection of technology, material selection and design of mold. An integral part of every design mold is a simulation of injection, which is also included. In conclusion of thesis is the calculation of the various stages of production and operation of the injection mold.

In-situ vapor extraction is performed by applying a pressure differential across a hydrophobic porous membrane that forms a wall of the channel as a means of reducing the local quality of flow boiling within the channel. As the local quality is reduced, the heat transfer capability can be improve while large pressure drops and flow instability can be mitigated. The present study investigates the potential of vapor extraction, by examining the characteristics and mechanisms of extraction. The physics based models for transition among extraction regimes are developed which can be used as a basis for a regime-based vapor extraction rate model. The effects of vapor extraction on flow boiling in a microscale fractal-like branching network and diverging channels are studied by using a one-dimensional numerical model based on conservation of mass and energy, along with heat transfer and pressure drop correlations. The results show the improvement in reduced pressure drop and enhanced flow stability, and show the potential of heat transfer enhancement. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from March 25, 2013 - March 25, 2014