Underwater Remote Welding Technology for Offshore Structures

The construction of offshore structures, equipment and devices requires a high level of mechanical reliability in terms of strength, toughness and ductility. One major site for mechanical failure, the weld joint region, needs particularly careful examination, and weld joint quality has become a major focus of research in recent times. Underwater welding carried out offshore faces specific challenges affecting the mechanical reliability of constructions completed underwater. The focus of this thesis is on improvement of weld quality of underwater welding using control theory. This research work identifies ways of optimizing the welding process parameters of flux cored arc welding (FCAW) during underwater welding so as to achieve desired weld bead geometry when welding in a water environment. The weld bead geometry has no known linear relationship with the welding process parameters, which makes it difficult to determine a satisfactory weld quality. However, good weld bead geometry is achievable by controlling the welding process parameters. The doctoral dissertation comprises two sections. The first part introduces the topic of the research, discusses the mechanisms of underwater welding and examines the effect of the water environment on the weld quality of wet welding. The second part comprises four research papers examining different aspects of underwater wet welding and its control and optimization. Issues considered include the effects of welding process parameters on weld bead geometry, optimization of FCAW process parameters, and design of a control system for the purpose of achieving a desired bead geometry that can ensure a high level of mechanical reliability in welded joints of offshore structures. Artificial neural network systems and a fuzzy logic controller, which are incorporated in the control system design, and a hybrid of fuzzy and PID controllers are the major control dynamics used. This study contributes to knowledge of possible solutions for achieving similar high weld quality in underwater wet welding as found with welding in air. The study shows that carefully selected steels with very low carbon equivalent and proper control of the welding process parameters are essential in achieving good weld quality. The study provides a platform for further research in underwater welding. It promotes increased awareness of the need to improve the quality of underwater welding for offshore industries and thus minimize the risk of structural defects resulting from poor weld quality.

Centros Financieros Offshore

Como consecuencia de los procesos de desregulación financiera y la creciente movilidad de flujos financieros internacionales; los centros financieros offshore se han consolidado dentro de la dinámica económica mundial, generando tanto beneficios a sus usuarios como criticas respecto a su instrumentalización para el financiamiento de actividades delictivas y terroristas; tornándose de esta manera en uno de los temas de mayor interés y debate en sus aspectos jurídicos y económicos; por lo que en el presente trabajo lo abordaremos desde la perspectiva jurídica, explicando la dinámica de su funcionamiento a partir de las distintas modalidades en que se desarrolla teniendo como base tanto la legislación nacional, internacional y los casos prácticos de las actividades que realizan dichos países.

Mortality of Migratory Birds from Marine Commercial Fisheries and Offshore Oil and Gas Production in Canada

There is an imminent need for conservation and best-practice management efforts in marine ecosystems where global-scale declines in the biodiversity and biomass of large vertebrate predators are increasing and marine communities are being altered. We examine two marine-based industries that incidentally take migratory birds in Canada: (1) commercial fisheries, through bycatch, and (2) offshore oil and gas exploration, development, and production. We summarize information from the scientific literature and technical reports and also present new information from recently analyzed data to assess the magnitude and scope of mortality. Fisheries bycatch was responsible for the highest levels of incidental take of migratory bird species; estimated combined take in the longline, gillnet, and bottom otter trawl fisheries within the Atlantic, including the Gulf of St. Lawrence, and Pacific regions was 2679 to 45,586 birds per year. For the offshore oil and gas sector, mortality estimates ranged from 188 to 4494 deaths per year due to the discharge of produced waters resulting in oil sheens and collisions with platforms and vessels; however these estimates for the oil and gas sector are based on many untested assumptions. In spite of the uncertainties, we feel levels of mortality from these two industries are unlikely to affect the marine bird community in Canada, but some effects on local populations from bycatch are likely. Further research and monitoring will be required to: (1) better estimate fisheries-related mortality for vulnerable species and populations that may be impacted by local fisheries, (2) determine the effects of oil sheens from produced waters, and attraction to platforms and associated mortality from collisions, sheens, and flaring, so that better estimates of mortality from the offshore oil and gas sector can be obtained, and (3) determine impacts associated with accidental spills, which are not included in our current assessment. With a better understanding of the direct mortality of marine birds from industry, appropriate mitigation and management actions can be implemented. Cooperation from industry for data collection, research to fill knowledge gaps, and implementation of mitigation approaches will all be needed to conserve marine birds in Canada.

Modelling the torsional interaction of wire and polyester fibre ropes used for offshore moorings

Oil rig mooring lines have traditionally consisted of chain and wire rope. As production has moved into deeper water it has proved advantageous to incorporate sections of fibre rope into the mooring lines. However, this has highlighted torsional interaction problems that can occur when ropes of different types are joined together. This paper describes a method by which the torsional properties of ropes can be modelled and can then be used to calculate the rotation and torque for two ropes connected in series. The method uses numerical representations of the torsional characteristics of both the ropes, and equates the torque generated in each rope under load to determine the rotation at the connection point. Data from rope torsional characterization tests have been analysed to derive constants used in the numerical model. Constants are presented for: a six-strand wire rope; a torque-balanced fibre rope; and a fibre rope that has been designed to be torque-matched to stranded wire rope. The calculation method has been verified by comparing predicted rotations with measured test values. Worked examples are given for a six-strand wire rope connected, firstly, to a torque-balanced fibre rope that offers little rotational restraint, and, secondly, to a fibre rope whose torsional properties are matched to that of the wire rope.

Economic valuation of an offshore wind farm in Greece: the role of individual’s base-state influences and beliefs in the value formation process

The increased concern for the impacts of climate change on the environment, along with the growing industry of renewable energy sources, and especially wind power, has made the valuation of environmental services and goods of great significance. Offshore wind energy is being exploited exponentially and its importance for renewable energy generation is increasing. We apply a double-bound dichotomous Contingent Valuation Method analysis in order to both a) estimating the Willingness to Pay (WTP) of Greek residents for green electricity produced by offshore wind farm located between the islands of Tinos and Andros and b) identifying factors behind respondents’ WTP including individual’s behaviour toward environment and individual’s views on climate change and renewable energy. A total of 141 respondents participated in the questionnaire. Results show that the respondents are willing to pay on average 20€ every two months through their electricity bill in return for carbon-free electricity and water saving from the wind farm. Respondents’ environmental consciousness and their perception towards climate change and renewable energy have a positive effect on their WTP.

GULF OF MEXICO'S OFFSHORE OIL PLATFORM WIND POTENTIAL

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Gulf of Mexico's Offshore Oil Platform Wind Potential

There are over 6000 natural resource drilling platforms in the Gulf of Mexico, all of which will become obsolete once their deposits are extracted. This study examined one of the possible alternate uses for these platforms, wind power potential. Using ArcGIS the number of platforms was reduced by weighting their distance from National Data Buoy Center wind speed collection points and water depth. Calculations were done to assess the optimal sites remaining, as well as provide an estimate of the energy potential for each site. Data for this project was obtained from the Minerals Management Service (MMS), United States Geological Service (USGS), and National Data Buoy Center (NDBC). A major limitation of this project was a lack of NDBC wind speed buoys, creating large data gaps and excluding many oil rigs that have otherwise high energy potential.

Estudo da susceptibilidade à corrosão sob tensão e à corrosão : fadiga do aço API X65 aspergido termicamente utilizado em componentes offshore

Aços de alta resistência mecânica, aspergidos termicamente, são os materiais mais adequados para garantir o bom desempenho de certos componentes de plataformas offshore, expostos a situações severas de carregamento em água do mar. A literatura apresenta vários estudos relativos ao efeito combinado entre esforços mecânicos e o meio agressivo, em aços de alta resistência, entretanto, poucos avaliam o desempenho desses aços aspergidos metalicamente. A susceptibilidade à corrosão sob tensão e à corrosão-fadiga, de um aço de alta resistência mecânica aspergido termicamente, empregado em componentes de plataformas offshore, foi avaliada mediante as técnicas de ensaio de tração com baixa taxa de deformação, ensaio de fadiga por flexão em três pontos e metalografia da fratura. Os ensaios foram realizados em água do mar sintética ao potencial de corrosão e à um potencial catódico, utilizando-se amostras de aço revestidas termicamente com zinco e alumínio pelo processo de aspersão com plasma spray. O comportamento de amostras ensaiadas ao ar foi usado como parâmetro para avaliação do desempenho do aço em água do mar. Os resultados obtidos indicam que o aço revestido é susceptível à corrosão sob tensão e à corrosão fadiga em água do mar, sendo que o mecanismo de fragilização envolve a ruptura prematura dos revestimentos e a participação do hidrogênio.

Ineficiências entre os mercados onshore e offshore de Renminbi

Autoridades chinesas tem buscado agir com rapidez, mas com costumeira cautela, para que sua moeda seja capaz de adquirir status de moeda internacional de reserva. Embora tal objetivo exija eliminação ou considerável relaxamento dos controles de capitais, estes ainda existem e geram significativas distorções entre os mercados de câmbio e juros em Renminbi onshore, na China Continental, e offshore, em Hong Kong. Este trabalho descreve algumas destas distorções através da análise de instrumentos financeiros operados nos mercados à vista de moeda (Renminbi spot), forward de moeda (NDF de Renminbi), e de dívida governamental e corporativa em Hong Kong (Dim Sum Bonds).

Precificação de energia eólica offshore no Brasil

Offshore wind power emits low amounts of gases, is renewable and has better performance than onshore due to its greater stability and higher wind power density, less visual and noise impact, among others. Brazil has a high capacity of generation, but has not yet developed any offshore projects. High costs are a strong impediment. This study is an effort towards pricing offshore resources through Livelized Cost of Energy - LCOE, which represents the minimum return to cover the costs of development, production and maintenance of a wind project. Initially LCOE was calculated for all Brazilian onshore wind farms listed at Bloomberg New Energy Finance R○, accounting for 71 farms. Then hypothetical offshore wind farms were created from the onshore farms, tripling the cost of generation, which is consistent with the literature, and estimating the offshore energy for two locations off the Brazilian coast using satellite data extracted from National Oceanic and Atmospheric Administration. The results demonstrate that offshore resources have the potential to significantly reduce the energy price due to the better performance of the wind at sea

Teoria de carteiras e a alocação de parques eólicos offshore

The consumption of energy on the planet is currently based on fossil fuels. They are responsible for adverse effects on the environment. Renewables propose solutions for this scenario, but must face issues related to the capacity of the power supply. Wind energy offshore emerging as a promising alternative. The speed and stability are greater winds over oceans, but the variability of these may cause inconvenience to the generation of electric power fluctuations. To reduce this, a combination of wind farms geographically distributed was proposed. The greater the distance between them, the lower the correlation between the wind velocity, increasing the likelihood that together achieve more stable power system with less fluctuations in power generation. The efficient use of production capacity of the wind park however, depends on their distribution in marine environments. The objective of this research was to analyze the optimal allocation of wind farms offshore on the east coast of the U.S. by Modern Portfolio Theory. The Modern Portfolio Theory was used so that the process of building portfolios of wind energy offshore contemplate the particularity of intermittency of wind, through calculations of return and risk of the production of wind farms. The research was conducted with 25.934 observations of energy produced by wind farms 11 hypothetical offshore, from the installation of 01 simulated ocean turbine with a capacity of 5 MW. The data show hourly time resolution and covers the period between January 1, 1998 until December 31, 2002. Through the Matlab R software, six were calculated minimum variance portfolios, each for a period of time distinct. Given the inequality of the variability of wind over time, set up four strategies rebalancing to evaluate the performance of the related portfolios, which enabled us to identify the most beneficial to the stability of the wind energy production offshore. The results showed that the production of wind energy for 1998, 1999, 2000 and 2001 should be considered by the portfolio weights calculated for the same periods, respectively. Energy data for 2002 should use the weights derived from the portfolio calculated in the previous time period. Finally, the production of wind energy in the period 1998-2002 should also be weighted by 1/11. It follows therefore that the portfolios found failed to show reduced levels of variability when compared to the individual production of wind farms hypothetical offshore

Adição de vermiculita expandida mícron em pastas de baixa densidade para cimentação de poços de petróleo

The northeastern region of Brazil has a large number of wells producing oil using a method of secondary recovery steam injection, since the oil produced in this region is essentially viscous. This recovery method puts the cement / coating on thermal cycling, due to the difference in coefficient of thermal expansion between cement and metal coating causes the appearance of cracks at this interface, allowing the passage of the annular fluid, which is associated with serious risk socioeconomic and environmental. In view of these cracks, a correction operation is required, resulting in more costs and temporary halt of production of the well. Alternatively, the oil industry has developed technology for adding new materials in cement pastes, oil well, providing high ductility and low density in order to withstand the thermo-mechanical loads generated by the injection of water vapor. In this context, vermiculite, a clay mineral found in abundance in Brazil has been applied in its expanded form in the construction industry for the manufacture of lightweight concrete with excellent insulation and noise due to its high melting point and the presence of air in their layers lamellar. Therefore, the vermiculite is used for the purpose of providing low-density cement paste and withstand high temperatures caused by steam injection. Thus, the present study compared the default folder containing cement and water with the folders with 6%, 8% and 10% vermiculite micron conducting tests of free water, rheology and compressive strength where it obtained the concentration of 8 % with the best results. Subsequently, the selected concentration, was compared with the results recommended by the API standard tests of filtered and stability. And finally, analyzed the results from tests of specific gravity and time of thickening. Before the study we were able to make a folder with a low density that can be used in cementing oil well in order to withstand the thermo-mechanical loads generated by steam injection