bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribución territorial y consumo de botones de perforación en “V” en el ámbito argárico
Authors: López Padilla Juan A.
Published: October 2008

Los botones de perforación en V han sido tradicionalmente considerados como un elemento en cierto modo “intrusivo” en el repertorio artefactual argárico. Desde el punto de vista cronológico, su estrecha vinculación con el “fenómeno campaniforme” provocó una clara tendencia a relacionarlos exclusivamente con las etapas más antiguas del desarrollo de la sociedad argárica. No obstante, los datos recientemente proporcionados por la revisión de las excavaciones y del material arqueológico de cronología prehistórica procedentes de la Illeta dels Banyets de El Campello, en Alicante, permiten reconsiderar la producción y el consumo de estos objetos en el seno de la sociedad argárica tanto desde el punto de vista espacial como cronológico.
Ritual funerario y comensalidad en las sociedades de la Edad del Bronce del Sureste Peninsular: la Cultura de el Argar
Authors: Aranda Jiménez Gonzalo , Esquivel Guerrero José Antonio
Published: October 2008

En el presente trabajo se plantea el desarrollo de rituales de comensalidad asociados al ritual funerario argárico. Las evidencias arqueológicas de estos rituales estarían relacionadas por una parte con la producción de un conjunto normalizado de vasijas cerámicas asociadas con la presentación y consumo de alimentos y bebidas, y en donde destacan sus propiedades visuales relacionadas con prácticas sociales de exhibición y escenificación. Por otra parte, la aparición de restos faunísticos en las sepulturas argáricas supone que, como parte de ritual, se procedió al sacrificio de bóvidos u ovicápridos, fundamentalmente en edades jóvenes de los que una parte, los extremos distales, fueron introducidos en las tumbas. El resto de la especie o especies sacrificadas, en un momento óptimo para su consumo, serían consumidas como parte de los rituales de comensalidad. El acceso socialmente diferenciado a estas prácticas comensales contribuiría a la creación de un sentido de comunidad al tiempo que se escenifican y naturalizan unas relaciones sociales claramente desiguales.
Estudio tipológico y funcional de las toberas del yacimiento de la Fonteta (Guardamar del Segura, Alicante)
Authors: Renzi Martina
Published: October 2008

El yacimiento fenicio de La Fonteta (Guardamar del Segura, Alicante), gracias sobre todo al descubrimiento de numerosos vertederos metalúrgicos, ha proporcionado abundantes materiales relacionados con la producción de hierro, cobre, cobre/plomo y bronces binarios y ternarios, y probablemente también con la obtención de plomo y de plata. Entre estos restos arqueometalúrgicos hay que destacar por cantidad y variedad un significativo conjunto de toberas, constituido por más de 400 fragmentos. Las piezas documentadas hasta ahora se enmarcan en un arco cronológico que va desde los comienzos del siglo VIII a.C. hasta finales del siglo VII a.C. Actualmente, este conjunto de toberas se puede considerar el más abundante y variado conocido en un yacimiento fenicio de la Península Ibérica, y el estudio de este material nos permitirá definir la variabilidad de las formas y observar si ese cambio formal responde a algún factor tecnológico vinculado con actividades metalúrgicas o con el tipo de producto metálico procesado. Para ello, en este artículo definiremos los tipos, su frecuencia en las diferentes fases, su contexto de aparición y, en los casos en los que haya sido posible, se presentarán los resultados obtenidos por el análisis elemental de los restos escoriaceos adheridos a las bocas de estas toberas.
Redefiniendo el registro material. Implicaciones recientes desde la arqueología del paisaje anglosajona
Authors: Soler Segura Javier
Published: October 2008

Tras examinar brevemente la evolución en el ámbito anglosajón de las definiciones de registro arqueológico, así como del proceso por el cual se va conceptualizando lo espacial en la disciplina, se argumenta que el paisaje se concibe como otra manera de ampliar las definiciones manejadas de registro. Rastreados ambos procesos se analiza, tras concretar algunos de sus referentes teóricos, qué es lo que actualmente se entiende en Arqueología por paisaje, así como la manera en que se está abordando. De esta forma se concretan y valoran sus singularidades, se rastrean algunas de las influencias que han llevado a plantear el problema del paisaje y se evalúan las repercusiones que sus afirmaciones suponen para el estudio del pasado en Arqueología.
Sociedad, ideología y entornos construidos durante la Protohistoria del Oriente Meseteño: el caso de El Ceremeño de Herrería
Authors: Arenas Esteban J. A.
Published: October 2008

La aplicación de esquemas teórico-metodológicos aportados por la Arqueología del Paisaje está dotando a los estudios sobre el mundo prerromano peninsular de unas herramientas de gran utilidad para aproximarnos a los patrones de racionalidad imperantes en aquella época. No obstante, estos planteamientos todavía no han encontrado un eco sustancial en la investigación sobre las culturas prerromanas del Oriente de la Meseta, donde las excavaciones y prospecciones desarrolladas en los últimos años están aportando un volumen de información especialmente valioso para acometer este tipo de análisis. Por esta razón, el presente artículo se centra en una lectura de la dimensión social y simbólica de los sucesivos entramados urbanos documentados en el poblado pre-romano de El Ceremeño de Herrería (Guadalajara, España). Se analiza la configuración de los distintos espacios allí construidos, considerando primero las relaciones estructurales y funcionales que las distintas construcciones guardan entre sí dentro del asentamiento, y analizando más tarde las que éste guarda con otros enclaves del entorno.
La evolución del uso de soportes líticos en la secuencia Tardiglaciar de la Cueva de El Rascaño (Mirones-Cantabria)
Authors: Chauvin Adriana
Published: October 2008

La finalidad del presente trabajo es evaluar la producción y selección para el retoque de los soportes líticos a lo largo de la secuencia Tardiglaciar de la cueva de El Rascaño. Para el análisis, se seleccionó una muestra a la que se aplicó una serie de criterios tipométricos y de análisis tecnológico. Con estos elementos se evaluó cuál era el objetivo de la producción en cada nivel y cuál fue su variación en el tiempo.
El poblado Calcolítico de Camino de las Yeseras (San Fernando de Henares, Madrid): un escenario favorable para el estudio de la incidencia campaniforme en el Interior Peninsular
Authors: Blasco Concepción , Delibes Germán , Baena Javier , Liesau Corina , Ríos Patricia
Published: October 2008

El trabajo ofrece una primera aproximación al Yacimiento Calcolítico de Camino de Las Yeseras donde se ha documentado una ocupación a lo largo del III milenio que, en el tránsito al II milenio AC, acoge a grupos poseedores de cerámica campaniforme que renuevan los equipos materiales con la explotación de nuevos recursos líticos, adaptan su cabaña a una mejor movilidad y practican rituales funerarios diversificados dentro del poblado. El marco temporal se avala con una importante secuencia de dataciones de C14 y TL, plenamente coincidentes.
Factores visuales de localización de los monumentos megalíticos de la Cuenca del Sever (Portugal- España)
Authors: López-Romero González de la Aleja Elias
Published: October 2008

Dentro de los estudios de análisis del territorio el comportamiento visual de los yacimientos arqueológicos juega un papel fundamental para la comprensión de las estrategias de ocupación del espacio. En el caso que ahora nos ocupa, el objeto de estudio viene dado por las diferentes manifestaciones de la monumentalidad neolítica de la cuenca del Sever (Portugal-España). La consideración de distintos factores que entran en juego en la visibilidad nos permite valorar el papel jugado por la topografía, las estructuras arquitectónicas y las distintas relaciones entre éstas; la importancia de la variabilidad microtopográfica como factor de limitación a la visibilidad, o las particularidades de localización respecto al entorno inmediato de los monumentos son algunos de los puntos a destacar dentro de la cuenca.
Dinámica social, paisaje y teoría de la práctica Propuestas sobre la evolución de la sociedad ibérica en el área central del Oriente Peninsular
Authors: Grau Mira Ignacio
Published: October 2008

Recientes estudios sobre los paisajes de la Edad del Hierro en el área de la Cultura Ibérica han permitido elaborar sólidos modelos teóricos sobre la dinámica social de sus distintas comunidades. Partiendo de estos planteamientos, en especial del modelo de sociedad clientelar desarrollado por Ruiz y Molinos, proponemos nuevos matices y analizamos la dinámica social del área oriental de Iberia. Adoptamos una postura basada en la teoría de Agency con la finalidad de comprender el desarrollo del modelo social y las variaciones observadas debidas, en nuestra opinión, a la participación de los agentes. A través del análisis del paisaje y elementos significativos que se relacionan con la materialización de la ideología, exploramos la estructura de la sociedad ibérica en la región de estudio.
Nuevas aportaciones sobre el fragmento cerámico
Authors: Domingo Sanz Inés , Roldan García Clodoaldo , Ferrero Calabuig José , García Borja Pablo
Published: October 2008

La coloración rojiza de la superficie externa del fragmento cerámico con decoración de cervidos incisos de la Cova de l’Or se ha interpretado tradicionalmente como evidencia de la aplicación de la técnica de la almagra. Sin embargo, el análisis elemental del fragmento y la comparación de los resultados con los obtenidos a partir de otro fragmento con decoración a la almagra del mismo yacimiento, permite cuestionar la utilización de dicha técnica en el primero de ellos. Así mismo, la búsqueda de paralelos para los motivos esquemáticos incisos del vaso, tanto entre las decoraciones cerámicas como en arte parietal, nos lleva a sugerir que más que ciervos pudiera tratarse de representaciones de ciervas.
Dimensiones naturales y sociales de la producción de hachas de piedra en el noreste de la Península Ibérica
Authors: Risch Roberto , Martínez Fernández Francisco
Published: October 2008

En comparación con otras zonas de Europa occidental, la península Ibérica se caracteriza por una notable escasez de evidencias relativas a la producción de hachas pulimentadas prehistóricas. El presente artículo aborda esta problemática a partir del estudio de la fabricación y la distribución de útiles de corneana en el noreste peninsular. La combinación de análisis petrográficos y geomorfológicos, así como la consideración de un tipo de materiales arqueológicos poco conocidos hasta el momento permite identificar las áreas de extracción de las materias primas y las estrategias de fabricación de los esbozos. Asimismo, se aborda el valor social de los productos tal como se expresa en su asociación con otros materiales ampliamente distribuidos durante el Neolítico. Las asimetrías geográficas y sociales observadas conducen a la cuestión de las estructuras de poder en sociedades neolíticas.
Modelos regionales de producción metalúrgica en Asia Occidental en el calcolítico Bronce Antiguo y Medio
Authors: Avilova Liudmila
Published: October 2008

El objetivo de este trabajo es la reconstrucción y análisis comparativo de modelos regionales de producción metalúrgica del Calcolítico y la Edad del Bronce Inicial y Media. Se basa en el análisis estadístico de una base de datos única sobre hallazgos metálicos de cuatro regiones del Próximo Oriente: Anatolia, Mesopotamia, el Levante e Irán. Los materiales se analizan atendiendo a cuatro variables: períodos cronológicos, función de los artefactos, proporción de los metales usados y las distintas aleaciones del cobre. La autora aporta una serie de conclusiones respecto a las precondiciones para los inicios de la producción metalúrgica en el Oeste Asiático; sobre el papel pionero de Irán en su aparición; la importancia de los piedemontes en su desarrollo; el patrón no continuo que se observa en las dinámicas de producción por periodos; y su relación con la expansión de la economía de producción, el intercambio a larga distancia y la aparición de las primeras civilizaciones.
Arte mueble en el Auriñaciense cantábrico. Nuevas aportaciones a la contextualización del frontal grabado de la cueva de Hornos de la Peña (San Felices de Buelna, Cantabria)
Authors: Tejero José Miguel , Cacho Carmen , De Quirós Federico Bernaldo
Published: October 2008

El hueso frontal de équido grabado con una representación de este mismo animal procedente de la Cueva de Hornos de la Peña (Cantabria), se recuperó a principios del pasado siglo XX en las excavaciones de H. Breuil, H. Obermaier y H. Alcalde del Río. A pesar de la atribución auriñaciense de sus excavadores, las diferentes publicaciones posteriores en que la pieza ha sido objeto de análisis, han mantenido siempre la duda de su pertenencia a este tecnocomplejo. A ello ha contribuido el hecho de que la estratigrafía de Hornos de la Peña no ha podido ser hasta el presente estudiada en profundidad, como también, muy probablemente, el carácter naturalista de su representación que parece alejarlo de los presupuestos artísticos del Paleolítico Superior inicial cantábrico. En este trabajo presentamos una serie de datos sobre la estratigrafía del yacimiento, obtenidos de diversos documentos inéditos conservados en el archivo del Museo Arqueológico Nacional de Madrid que, a nuestro juicio, corroboran la pertenencia de esta pieza de arte mueble al Auriñaciense.
Un pequeño campamento minero de la Edad del Bronce: La Loma de la Tejería (Albarracín, Teruel)
Authors: Montero Ruiz Ignacio , Rodríguez de la  Esperanza María Jesús
Published: October 2008

Se presentan los datos de las excavaciones realizadas en la Loma de la Tejería (Albarracín, Teruel) en la que se documenta un campamento estacional vinculado a tareas minero-metalúrgicas de pequeña escala. Los estudios realizados sobre el material indican el aprovechamiento de los recursos geológicos locales tanto de mineral de cobre, como de arcillas del Keuper con Jacintos de Compostela y rocas volcánicas. Los análisis de residuos han documentado en la cerámica productos lácteos y bebidas alcohólicas. Cronológicamente el yacimiento se encuadra en el Calcolítico y Bronce Antiguo, con presencia de cerámica campaniforme.
El Túmulo 20 de la necrópolis Ibérica de Tútugi (Galera, Granada)
Authors: Rodríguez-Ariza Mª Oliva , Gómez Cabeza Francisco , Montes Moya Eva
Published: October 2008

Se presentan aquí los resultados obtenidos de la excavación del Túmulo 20 de la Necrópolis ibérica de Tútugi. Este túmulo fue saqueado en 1916 y los materiales fueron recuperados y publicados por Cabré y Motos en 1920, entre ellos se encontraba la Dama de Galera. La excavación ha puesto al descubierto un complejo estructural con dos fases constructivas. La primera fase consta de una cámara cuadrangular con pasillo de acceso, ambos excavados en la roca, y con un pilar central de adobe que posiblemente sostenía el techo. En una segunda fase la cámara es rellenada por piedras y tierra y se recortaría la roca para conformar una plataforma circular de 13 m de diámetro que es pintada de rojo. En el centro de esta plataforma se construye, como proyección de las estructuras subterráneas, un espacio cuadrangular con corredor de entrada. Este edificio al aire libre queda enmarcado dentro de la plataforma por la forma del lingote chipriota pintado en blanco.
Glomar Challenger - Deep Sea Drilling From Texas To Dakar
Authors: Field A.J. , Thornburg Russell B. , Crooke R. Curtis
Published: October 2008

Introduction

The paper "Glomar Challenger - Deep Sea Drilling From Texas To Dakar" consists of a recently completed documentary film covering project background, and design construction and operation of the Glomar Challenger during the initial legs of the Deep Sea Drilling Project.

The following notes are intended simply for the viewers information and possible future reference. The Deep Sea Drilling Project is a portion of this Government's Ocean Sediment Coring Program, directed towards obtaining deep sea cores for scientific analysis throughout the Atlantic and Pacific Ocean basins. The Project is an outgrowth of a proposal initially prepared by the JOIDES Group. Participants of JOIDES include Scripps Institution of Oceanography (currently Manager of the Deep Sea Drilling Project), Woods Hole Oceanographic Institute, Lamont Geological Observatory, The Institute of Marine Science and, a current addition, the University of Washington. The program is funded and administered by the National Science Foundation on behalf of the U. S. Government.

Initial drilling operations commenced on August 12, 1968 in the Gulf of Mexico, and are currently being carried out in the Caribbean prior to the start of operations in the Pacific Ocean in April, 1969. A summary of the highlights of the program to date (March, 1969) include the following:Number of locations occupied to date: 28Number of holes drilled to date: 49Maximum water depth drilled to date: 18,157 ft.Minimum water depth drilled to date: 6,355 ft.Maximum penetration into sea floor: (Hole 9A) 2, 759 ft.Maximum length of drill string: (Hole 28) 19,483 ft.Principal dimensions and characteristics of the Glomar Challenger are as follows:Length Over All: 402 ft.Beam: 65 ft.Molded Depth: 26 ft. 9 in.Designed Draft: 20 ft.Designed Displacement: 10,500 long tonsDynamic Positioning System

a. Twin main screws: 2250 hp per shaft (underway propulsion)

The Glomar Challenger is provided with a fully automatic position sensing and control system capable of maintaining the ship in position to an accuracy of ± 200 ft. in a 45 knot head wind combined with a 1 1/2 knot beam current.

The performance of the Glomar Challenger to date has been extremely satisfactory, and this significant step forward in advanced offshore drilling technology represents a remarkable achievement on the part of the offshore drilling industry.
The Offshore Mercury
Authors: Sharp Frank W.
Published: October 2008

This paper describes the design process in the development of a new concept in exploratory drilling tools. It examines the requirements for satisfactory design of a ship in a drilling platform and an elevating system. The design efforts are brought together to form in one unit a cohesive drilling tool - the self propelled, self-elevating drill ship - The Offshore Mercury.

THE OFFSHORE MERCURY

The Offshore Mercury, the industry's first self-propelled and self-elevating drill ship, presents a new concept of mobility and stability in offshore exploratory drilling. It accomplishes the heretofore impossible combination of economical mobility comparable to the self-propelled drill ship with the superior stability and drilling reliability of the jack up platform. The realization of this new concept is the result of an extensive design effort. We wish to trace some design considerations involved in producing the Offshore Mercury.

The first consideration is mobility. In our phase of the industry, this means moving on the sea. Move a drilling operation at sea? Easy; mount it on a buoyant box. That is a start. Push or pull it with tug boats. We do that now essentially, but we have to depend on getting the tugs out on time and having good weather to tie the tugs on and, besides, it is expensive. Let us remove the dependence on tugs; do it ourselves and make a sizeable saving on trip insurance. We have plenty of power for the rig, so hook it up to propellers and go it alone - anytime we are ready - anywhere we want to go. There you have it - a self-propelled drill ship.

Almost. Let us backtrack to the point of the buoyant box that we mounted the drilling equipment on. Basically, a box that floats works out fine for the preliminary criteria. But how about the refinements that make the whole thing workable, such as how fast is a box, and how safe is this rig in rough weather? What makes a box a ship? First we must make the box big enough to carry the drilling equipment. Experience can tell us that the drill rig will be about the same size as our rig "Orion" in the North Sea. So, we first take an Orion-shaped box and look at the speed. Not too good at 3 to 4 knots even with those big tugs pulling all out. Must be something to do with the shape of the bow. "Orion" is blunt in the bow. Let us add some shape to the bow to make the water flow by more easily.

This was a problem for the naval architects and the model test tanks. They took some known relationships and came up with a double curvature surface which should suit the problem. They then put the idea into a wooden model and placed it in the test tank. Based on the results of this test, they predicted an obtainable speed of about 8 knots. This is a big improvement over Orion and her tugs.
Wave-Structure Interaction In Offshore Platforms
Authors: Rivas Alberto Gomez
Published: October 2008

The analysis of the complex interaction of wave forces and structural response is in its very early stages of development. Formulating the equation of motion for the structure under the action of wave forces involves the following uncertain parameters: [1] virtual water mass, which is a function of the relative velocities of the wave and the structure, and [2] drag forces, which are also a function of the relative velocities. Basic research is now needed to formulate a satisfactory equation of motion for the structure, based on these parameters. A computer model was developed to predict the dynamic response of structure inthe wave environment. Models were built and tested to check the computer model. The analytical and experimental results demonstrated the importance of the virtual mass and drag forces in formulating the equation of motion.

INTRODUCTION

The reliable prediction of the response of an offshore platform to wave action requires knowledge about the interaction of the wave and the structure during motion. With the structural system defined for its topological and mechanical characteristics and with the wave known or estimated, response follows from application of proper theory.

The design and construction of harbors is one of the oldest engineering applications. Ever since the port of A-ur was built on the Nile prior to 3000 B.C., there has been a continuous search for an understanding of the forces exerted by waves on marine structures. The forces exerted by waves on circular piles, plates, barge-like structures, vertical walls and breakwaters have been predicted by analytical methods and measured in the laboratory. The consensus of the investigators is that water particle velocity and acceleration are the governing parameters of the hydrodynamic forces exerted by waves on structures.

It should never be overlooked that the investigators always mean relative velocity of the water particle with respect to the body upon which the force is exerted. The same statement is true with regard to accelerations. This fact is often overlooked because most structures used in harbor engineering are very rigid and consequently the water velocities and accelerations with respect to the body are numerically equal to the velocities and accelerations with respect to ground. This is not the case for some offshore platforms that are flexible enough to have velocities and accelerations in the same order of magnitude as the water velocities and accelerations.

Fig. la presents a cylinder rigidly attached to a stiff support. The force F exerted by the wave on the cylinder can be computed by the formula proposed by Morison, O'Brien, Johnson and Shaaf.2F = Cl V2 L + C2 A L,..... [1]

where V and A are the water particle velocity and acceleration, respectively; Cl and C2 are constants defined by the geometry of the body, in this case a cylinder; and L is the length of the cylinder.

Since the cylinder is rigidly attached to the supports of infinite stiffness, its displacement under the action of the wave forces is zero.
Modal Study of a Submerged Buoyant Tank in Waves
Authors: Wiegel R.L. , Dilley R.A. , Whisenand S.F. , Williams J.B.
Published: October 2008

One possibility for storing the oil produced by an offshore well is to make use of a moored submerged buoyant tank. Tests were conducted with a 1:49 scale model of such a tank, with neutral buoyancy mooring lines, in the 6 ft. deep by 8 ft. wide by 200 ft. long Wave-Towing Tank, University of California, Berkeley, under contract to the California Research Corporation (presently the Chevron Research Corporation).

The "prototype" was a circular cylinder approximately 190 ft. long by 22½ ft. in diameter with hemispherical heads, with an empty weight of 874 kips, and with a 60½ ft. longitudinal radius of gyration. Two general series of tests were conducted:Vertical mooring lines only, andvertical, breast, bow, and stern mooring lines.

The "prototype" water depth was 245 ft. and the top of the submerged tank was 185 ft. above the bottom Measurements were made of mooring line forces and tank motions with the model in head, quartering, and beam seas.

For the case of vertical mooring lines only, it was found that the dynamic force in the mooring lines due to wave action could be predicted rather well for beam seas by use of the "wave force on a pile" theory. Furthermore, it was found that the limits of dynamic forces could be predicted for the model in head seas using the same theory. The high forces measured in the vertical mooring lines due to a shifting of the buoyancy load from one line to another, when they were not exactly parallel, leads to the conclusion that extreme care will be necessary during installation. The greatest motion of the tank occurred in head seas in waves of 21 sec., prototype (the same value as the natural period of surge of the moored tank), with the surging motion of the tank being as much as 6 times the wave height and 4 times the total horizontal motion of the surface water particles.

When breast, bow, and stern mooring lines were added to the system, the motion of the submerged buoyant tank became negligible. It was found, however, that at some point in the transference of the buoyant force from the vertical to the lateral mooring lines (the percentage load transference depending upon the wave height and period to which the system was subjected) the vertical mooring lines would just slacken at one point in the cycle. This resulted in an impact type of loading upon take-up with high forces and considerable vibration. The magnitude of the peak force under these conditions could not be estimated due to the response characteristics of the force recording system.

SUBMERGED BUOYANT TANK MODEL MOORING LINES

A plexiglass tube was used for the tank and aluminum tubes were used for the mooring lines. Availability of plexiglass tube sizes (one being 5.5 in.O.D., 1/8 in. wall thickness) fixed the scale at 1:49 as the closest possible to the desired scale. This geometric scale fixed the time scale as 1:7.0 and the force scale at 1:117,650.*
Extraction of Methane from Oceanic Hydrate System Deposits
Authors: Max Michael  D. , Cruickshank Michael J.
Published: October 2008

No one to date has outlined an economic and safe method for sustained recovery of methane from the newly discovered low-grade oceanic hydrate and associated gas deposits. The potential rewards of unlocking the methane hydrate energy bank are potentially very great. The prize is possibly centuries of energy independence for some industrial states including the United States and Japan, and developing countries such as India, which appear to have considerable deposits of methane hydrate immediately adjacent to their landmasses. A number of nations, including the United States, have established, or are considering establishing, national hydrate research programs.

Introduction

Oceanic hydrate system deposits, which include both methane hydrate and associated methane gas, are very large, but relatively low grade when compared with conventional hydrocarbon deposits. They differ in character from conventional hydrocarbon deposits in almost every respect except that they encompass significant concentrations of hydrocarbon. It is now not immediately obvious in detail exactly how the methane from oceanic hydrate and related gas deposits will be recovered. It is not even certain whether hydrate or associated gas, or both, will be the preferred initial and eventual best economic target.

We examine some of the emerging issues likely to govern hydrate recovery and seafloor stability, and suggest geological models for oceanic hydrate system exploitation.

Methane hydrate; its disposition and recognition

Methane hydrates(CH4?6.1(±0.1%)H2O] are found in the low temperature-low pressure regimes of permafrost regions and high pressure-moderate temperature (from just below zero degrees C up to about 35 °C max) in ocean sediments. Methane hydrate is stable in seafloors below about 450 meters water depth in open ocean with an average temperate hydrothermal profile that gives hydrate a wide pressure-temperature field of stability1. Methane molecules are compressed closely together in the hydrate lattice. 1 m3 of hydrate yields about 160 m3 CH4 at STP and a residue of 0.87 H2O m32.

The hydrate forms in a zone of thermodynamic equilibrium, the Hydrate Stability Zone (HSZ) that extends downward from the seafloor to some depth determined by increasing temperature (Fig. 1). The base of the HSZ is a phase boundary. At constant geothermal gradients the thickness of the hydrate stability zone increases with increasing water depth and increased pressure. Where higher molecular weight thermogenic gases, such as ethane, butane, or propane occur, the hydrate stability field expands considerably. 1% propane in the gas mixture, for instance, can reduce the pressure at which the hydrate forms by nearly 40%1.

Figure 1. Position of the HSZ with respect to the hydro-and geothermal gradients and the methane hydrate phase boundary.(Available in full paper)
Vision of Growth for Trinidad and Tobago Natural Gas Industry
Authors: Wight David G.
Published: October 2008

Trinidad and Tobago continues to develop a world-class natural gas industry as the economy transforms from a predominantly oil-based economy to one, increasingly fuelled by gas. The country is poised for significant additional growth in gas and gas-based industries as the relatively large gas resource pool continues to be enhanced through successful exploration and the discovery of new resources.

With its solid reserve base, stable political climate, reliable economy, proximity to market and competitive market focus, Trinidad and Tobago continues to enjoy as good as, if not a better opportunity set than any country in the world, for further developing the natural gas business. We, at BP Amoco, have had a mutually beneficial relationship with the government and people of Trinidad and Tobago and remain committed to partnering in the future development and growth of the energy business in Trinidad and Tobago.

Introduction

The Republic of Trinidad and Tobago has an oil and gas industry that predates the modern petroleum industry (Ref. 1). The first successful well was reportedly drilled in 1866 in south Trinidad. Commercial oil production began in 1908 and for the next sixty years the emphasis was on oil production. Natural gas was considered then more of a nuisance than a benefit, and the unavoidable associated gas produced with the oil was limited to providing fuel and gas lift for maintaining oil production.

Commercial use of natural gas began in 1959, when Federation Chemical Ltd., a subsidiary of W. R. Grace, pioneered the use of natural gas as a feedstock to manufacture anhydrous ammonia. The next historical milestone for natural gas came five years later when commercial consumption increased with the use of gas as a primary fuel for electric power generation. In 1969, Amoco Energy discovered significant gas reserves in its license area off the East Coast. This discovery was followed in 1975 by the formation of The National Gas Company (NGC) of Trinidad and Tobago. The NGC was chartered to manage and sell natural gas. In discharging their role, they have facilitated the impressive expansion of the natural gas industry that has been seen from 1990 to 1997. The following sections discuss the country's strong gas resource base, the Government's aggressive market pursuits, rapidly expanding infrastructure and the security of gas supply situation: all ingredients for creating a vision of significant growth in the natural gas industry.

Growth of the Natural Gas Industry in Recent Years

The Natural Gas industry in Trinidad and Tobago has demonstrated continuous growth with gas sales increasing by approximately eight percent per year from 1990 to 1997. The country's Minister of Energy and Energy Industries, Senator Finbar Gangar, in his address to the Centre for Global Energy Studies Conference in London (Ref. 2) was quoted as saying Currently, Trinidad and Tobago is in the midst of an intense industrialisation thrust, with a major focus on the utilisation of natural gas as the main driver of this thrust."
Future Development of Gas Industry of Trinidad and Tobago
Authors: Kin Frank Look , Harnanan Clarence
Published: October 2008

The paper presents a review of the development of the gasindustry in Trinidad and Tobago. The role of The National Gas Company of Trinidad and Tobago Limited in the development of this industry is discussed.

The paper reviews the upstream and downstream operations, the pipeline network system and future development in these aspects of the gas industry.

The factors which make Trinidad and Tobago an attractive country for foreign investor in the gas industry both at upstream development and gas utilization are examined.

The natural gas sector of the economy has become the leading economic sector due to the government's policies with respect to the use of the natural gas reserves and the promotion and development of a range of petrochemical and gas based industries and the provision of fiscal and other incentives. Given the present state of industrial development, the future development of this industry is of significant importance.

Historical Review

The history of the energy sector dates back to the latter part of the nineteenth century. The first successful oil well was drilled in South Trinidad in 1866 and commercial production commenced in 1908. During the period 1908 to the 1960's the emphasis was on the production of crude oil. Associated gas which was produced with the crude oil was considered a nuisance and flaring of natural gas was wide spread in the industry.

The natural gas industry in Trinidad and Tobago dates back to early 1940's when gas produced as associated gas was used as a fuel and for gas lifting operation. During this period natural gas was piped to the oil company's housing areas in Point Fortin, Penal, Forest Reserve, Palo Seco and Guayaguayare for water heating and cooking. Gas lift operations and gas injection for secondary recovery of crude oil were fairly widespread in the oil producing areas of Trinidad and at one time there were up to 20 compressor stations dedicated to this production method and pressure maintenance respectively.

Natural gas was first used commercially as a fuel for power generation at the Penal power station in 1953 and at Trinidad Cement Limited, Claxton Bay in 1954. In 1959, the establishment of the first anhydrous ammonia plant in the country by Federation Chemicals Limited was based on natural gas as a feedstock for the manufacture of ammonia. This was followed by the expansion of natural gas usage for country wide generation of electricity when the power plant in Port of Spain commenced use of natural gas in 1964. This growth in the demand for natural gas in the sixties required the development of the pipeline infrastructure to support the expanded use of natural gas. The first was the construction of a 16-inch pipeline from Penal to Port of Spain.

In 1968 the country's most significant discovery of natural gas off the south east coast of Trinidad was made by Amoco Trinidad Oil Company.
Deepwater Ocean Currents West of Britain: Measurements & Criteria Development
Authors: Spring Walt , Gu George , Gray Mike , Middlehurst Bill , Dello Stritto Frank J.
Published: October 2008

Tranche-6 in the Færoe-Shetland Channel is a deepwater site characterised by complex currents of potentially high magnitude. Preparation for drilling at Tranche-6 included development of extreme and operational environmental criteria. Wind and wave conditions could be estimated with adequate accuracy from existing hindcast studies. Information on ocean currents is in general lacking, and hindcast modelling for currents is not nearly as accurate as for waves. Measurement programs collected data near the site in June-November 1992 and April-September 1995. Recorded data confirm strong currents varying in direction with depth. The data are the basis for preliminary extreme criteria and generic current profiles used in operability studies. Realtime current measurements were also made during Tranche-6 drilling, which began in May 1998, to support station keeping and riser management decisions. A weakness in advisory capabilities exists due to the lack of reliable current forecasts.

Introduction

This paper summarises (1) ocean current data collection and criteria development in preparation for drilling activities at Tranche-6 and (2) measurement and use of current data during drilling.

The UK Frontier Licensing Round of June 1991 awarded the Tranche-6 blocks, in the Færoe-Shetland Channel, west of the Shetland Islands, to a partnership of Mobil North Sea Ltd operator), Elf Enterprise Exploration plc and Lasmo North Sea plc. The 11 lease blocks comprising Tranche-6 are UK 213/18, 19, 20, 23, 24 and 214/11, 12, 13,16, 17 and 18 (Figure 1). Tranche-6 water depths range from 1,100 to 1,500 metres (~3,600 to 5,000 feet). Since 1972 more than 140 wells have been drilled West of Shetland. Approximate water depths for most of these wells have ranged from 120 to 800 metres (400 to 2,600 feet). In late 1996, Shell drilled in 1,100 metres (3,700 feet) of water, in a block adjacent to Tranche-6. Drilling at Tranche-6 began in May 1998, from the semi-submersible, Jack Bates, in ~1,200 m of water.

To prepare for drilling at a deepwater, high current severe environment site, preliminary and feasibility studies, including current measurements at the site, were undertaken in 1992 through 1994. Throughout 1995 definition engineering studies and additional current measurements furthered preparations for drilling at the site. The study results were implemented throughout selection of the optimum vessel, acquisition of the necessary hardware and systems (ie, riser fairings, riser and casing restraint systems, station keeping advisory system, and enhanced ROVs), upgrades to the vessel, and development of operating procedures [1].

As of January 1999, two wells have been drilled at Tranche-6, both in approximately 1,200m. For both, real-time current measurements were made to support drilling and vessel operations. To avoid disruption to drilling, a unique deployment of instrumentation was attempted, with varying success as described in a later section.
Ursa TLP, Tendon & Foundation Design, Fabrication, Transportation and TLP
Authors: Digre Kris A. , Kipp Robert M. , Hunt Rupert J. , Hanna Shaddy Y. , Chan Jack H. , Rosen Vic , van der Voort Cees
Published: October 2008

Ursa is the largest TLP in the Gulf of Mexico having 98.000 tons displacement and is the deepest TLP in the world located in 3,800 feet-of-water, MC Block 809. The URSA tendon and foundation design, fabrication and installation were built on the wealth of experience of previously installed TLPs1,2,3,11. In this paper, we focus on the new challenges that had to be met for this record setting project. Unique features of the Ursa Tendons, Foundation and Installation include:More tendons, 16 (4/corner) versus 12 (3/corner);Larger tendons, 32"OD × 1.5" wall (compared to the previous 26" × 1.3" and 28" × 1.2" wall)Longer Tendon Main Body Sections than the previous TLP's, resulting in 283.5' individual sections. This reduced the number of connections required and offshore handling time.New tendon top connector devdoped for Ursa resulting in simpler operations and significant cost savings.The foundation system consists of 16 individual piles. They are 417' in length and 96" OD constructed from 60-ksi material.The potential for significant fatigue-damage accumulation due to pile driving required special design and fabrication solutions.Design, Construction, and Installation strategy developed early on helped reduce cycle time, cost, and accommodated changes during construction.On site temporary mooring of the TLP was accomplished using a Flex-Yoke system.Improved procedures for tendon handling, stabbing and tensioning were developed.

Introduction

The Ursa TLP tendon, foundation and installation design and fabrication extended over a period of 3 years. In order to meet the fast-tract project schedule, material orders had to be placed early, before design completion. Design decisions were focused on reducing both cost and schedule, taking advantage of learnings from the previous TLP's, Early attention was given to the TLP installation design to allow modifications to be incorporated into the planned schedule, tendon design and pile driving requirements.

The modification brought out by the site and water depth change6,7,9 were significant. New soil information had to be obtained, designs verified, installation procedures adjusted and schedules maintained.

Tendon Design, Fabrication and Transportation

TLP and Tendon Sizing

After concept selection in the summer of 1995, the TLPSIZE program was used to size and optimize the URSA TLP. For the initial site, the water depth was determined to be 3,950 feet. Later, due to the site relocation, the water depth was reduced to 3,S00 feet7. Cost optimization was focused on sizing the hull and tendons such that the minimum tendon bottom tension was slightly above zero and the tendon met stress, collapse, and fatigue design criteria with minimal steel cross section area and maximized buoyancy. The program was calibrated based on technical and cost data from the MARS TLP.
Comparison between Observed and Predicted Characteristics of Fatigue Cracks in North Sea Jackets
Authors: Vårdal O.T. , Moan T. , Hellevig N.-C.
Published: October 2008

This paper presents a method which utilises the inspection history / in-service observations to measure and improve the accuracy of fatigue analysis method. The method is exemplified by using more than 4000 NDT (Non Destructive Testing) inspection results in the period 1972 to 1995, including 600 platform years in the North Sea. Cracks were detected in 438 joints, while 181 joints have been found to contain propagating cracks ("fatigue cracks"). Each joint contains one or more cracks.

The observations of cracks are compared with theoretical predictions using a probabilistic fracture mechanics approach. The experience clearly demonstrates that the present tools for predicting fatigue crack growth give very uncertain but generally conservative estimates of the fatigue life. However, 1 to 3 percent of the components that have long fatigue life, have been observed to develop propagating cracks in a period, which is 20 years or less. For main structural and horizontal framing components the theory overpredicts the number of propagating cracks by a factor of approximately 3 while it predicts 70 to 80 percent of the propagating cracks observed.

Introduction

Fatigue is an important consideration for structures in areas with more or less continuous storms, such as in the North Sea, and especially for dynamically sensitive platforms. The gradual deterioration of strength due to crack growth makes it possible to apply design, inspection, maintenance and repair measures to ensure adequate safety. The first generation of jacket structures in the Norwegian part of the North Sea installed in the early seventies was not designed against fatigue failure. The degree of detail and quality of the analysis have been significantly improved since 1975. The methods of fatigue analysis referred to in this paper are typical for approaches used after 1990.1,2

There is a significant scatter in the different fatigue analysis approaches used during design and maintenance2. Differences in the methods, in particular where used to determine wave kinematics in the splash zone, hydrodynamic loads, deterministic vs. stochastic wave modelling, pile-soil flexibility, and SCF's as a function of geometry and load pattern, may cause a variability in fatigue life estimates of one to two orders of magnitude1. The inspection and maintenance engineers' reluctance to solemnly focus on fatigue life estimate as a basis for the long term planning work is not only based on this significant uncertainty, but also on observed conservatism.
Starting Right: Sable Offshore Energy Project's HFE Program
Authors: Robertson Neil L.
Published: October 2008

Human Factors Engineering (HFE) is the integration and application of scientific knowledge about people, facilities and management systems in order to improve their interaction in the workplace. The application of human factors contributes to the effectiveness of work systems by improving productivity and safety, and reducing the potential for human errors.

In other words, human factors is the systematic process of designing equipment, facilities, and the work environment for human use.

This paper focuses on the HFE program as developed for the Sable Offshore Energy Project (Sable). It details the various components of the program, the overall impact on the project and how the program was structured to support the multiple engineering, fabrication and construction locations throughout North America and Europe.

Consideration of HFE in front-end planning ensured that its philosophies were incorporated in all project phases. This allowed Sable to incorporate HFE in the base design, enhancing, economically, operational safety. HFE was involved in all aspects of the project, from conceptual design, vendor selection and detailed engineering, to construction and commissioning.

This paper documents the overall HFE program, from its initial introduction to venture management, to its integration in engineering, procurement and construction. Lessons learned from the Sable program will be presented.

Introduction

In May 1996, the proponents (owners) of the Sable Offshore Energy Project agreed to proceed with the front-end engineering design (FEED) of a new, large scale, onshore and offshore development. The Sable owners are:Imperial Oil LimitedMobil Oil Canada Properties (lead operator)Shell Canada Limited (joint operator)Nova Scotia Resources (Ventures) LimitedMosbacher Operation Ltd

The Sable project, located in the Nova Scotia offshore region, will provide up to 600 Mscfd of offshore gas production and onshore processing to access the estimated 3.0 TCF in Scotia Shelf reserves. Appendix A provides a detailed description of the project.

As the pioneer gas development in this area, Sable provided a relatively rare opportunity to incorporate HFE concepts into the base design and philosophy of a new operation. Gas production, processing and distribution infrastructure did not exist in Nova Scotia, and only conceptual designs for the project had been established. Therefore, the FEED teams had no area-specific design precedent to follow and looked to the project owners for direction.

Supportive Environment.

While the opportunity to implement HFE into the Sable design existed, it would have been very difficult to proceed without a supportive environment.