bluuebunny/crossref_metadata_2025 huggingface dataset:
Estudio de polvos y recubrimientos metaestables de NiTi obtenidos por proyección térmica de plasma
Authors: Cano I. G. , Cinca N. , Dosta S. , Guillemany J. M.
Published: October 2008

El compuesto intermetálico de NiTi es conocido por su capacidad de memoria de forma así como por su pseudoelasticidad. Debido, además, a su alta resistencia a corrosión (biocompatiblidad), la gran mayoría de estudios se centran en su uso para aplicaciones médicas. Dentro del conjunto de las tecnologías de superficie, las investigaciones actuales utilizan la técnica de Proyección Térmica de Plasma al Vacío para producir recubrimientos de NiTi con contenidos mínimos de porosidad y de óxidos.El Centro de Proyección Térmica se planteó como objetivo la obtención de polvos y recubrimientos metaestables de NiTi a través de la técnica de Proyección de Plasma acoplado a un sistema de refrigeración con nitrógeno líquido. Se estudiaron dos polvos con diferentes características, pero de la misma composición nominal (Ni-45 % peso Ti). Uno de ellos, es el resultado de una mezcla directa de partículas de níquel y de titanio, mientras que el otro consiste en una aleación obtenida a través de un proceso de atomización por gas. Ambos polvos fueron proyectados, obteniéndose mejores resultados para el polvo atomizado, ya que ha permitido la obtención de recubrimientos en los que la fase de NiTi es la mayoritaria con un mínimo contenido en óxido. Para lograrlo, se ensayaron diferentes parámetros de proyección.La caracterización microestructural se llevó a cabo mediante microscopía electrónica de barrido con un sistema de microanálisis acoplado. Además, los estudios de difracción de rayos X permiten concluir que el ensanchamiento de los picos puede demostrar la existencia de metaestabilidad en los recubrimientos obtenidos.
Comportamiento a fatiga de uniones a solape simple con adhesivo epoxi de acero y acero prepintado
Authors: Bermejo R. , Oñoro J. , García-Ledesma R.
Published: October 2008

Las propiedades mecánicas de las uniones adhesivas no solo dependen de la naturaleza y propiedades de los adhesivos; hay muchos otros parámetros que influyen directamente en el comportamiento de las uniones adhesivas. Algunos de los más significativos son: el acabado superficial de los materiales, área y espesor de la capa adhesiva, un diseño adecuado, secuencia de aplicación, propiedades químicas de la superficie y preparación de los sustratos antes de aplicar el adhesivo. La resistencia mecánica de las uniones adhesivas está íntimamente relacionada con el proceso de rotura, directamente dependiente del mecanismo cohesión-adhesión. El objeto de este trabajo es analizar la influencia de dos acabados superficiales diferentes, sobre el comportamiento a fatiga de uniones con adhesivo epoxi. Los resultados muestran que la compatibilidad química entre el adhesivo y la capa prepintada mejora la adhesión de las uniones y la resistencia mecánica frente a cargas estáticas y dinámicas. Se ha obtenido el límite de fatiga para las uniones de ambas superficies.
Revisión sobre recubrimientos láser de aleaciones de aluminio
Authors: Pérez-Artieda M. G. , Fernández-Carrasquilla J.
Published: October 2008

En este artículo se presenta un trabajo de revisión bibliográfica, centrado en los procesos de recubrimiento y tratamiento superficial láser realizados en aleaciones de aluminio. Estos procesos láser son técnicas de modificación superficial que permiten la obtención de propiedades adecuadas en la superficie de componentes cuyas características internas no se ven afectadas. La ventaja principal que caracteriza la tecnología láser es la elevada velocidad de calentamiento y enfriamiento que se produce durante los procesos. Esto, provoca la formación de fases fuera del equilibrio, con microestructuras nuevas. En el artículo se aprecia que los resultados obtenidos, sin embargo, varían no sólo con el tipo de aleación utilizada como substrato y con el material de aporte sino, también, con la ruta de fabricación seguida por el propio material. Además, se analizan los diferentes parámetros que tienen influencia en el proceso y se contrastan las características obtenidas por distintos investigadores, con el objeto de condensar en un documento la información más importante en este campo
Dataciones radiocarbónicas en la Protohistoria del Sudoeste de la Meseta Norte. Consideraciones para un trabajo por hacer
Authors: López Jiménez Óscar
Published: October 2008

La evidencia arqueológica en el territorio que se extiende entre el valle del Río Tormes y el del Côa es relativamente amplia y variada. Sin embargo, la investigación ha sido escasa, descompensada y realizada con medios antiguos. De todos los yacimientos correspondientes a la Prehistoria Final y Protohistoria investigados (cerca de 70) hasta la fecha, tan solo cinco de ellos cuentan con dataciones radiocarbónicas a tener en cuenta, en algunos casos con una sola datación y en otros con ciertas anomalías que hacen, cuando menos, que se deban de poner en cuestión. Este trabajo pretende mostrar la realidad de la evidencia disponible y proponer algunas cuestiones de aplicación que deben de ser tenidas en cuenta para el desarrollo de trabajos posteriores. Es proritario conseguir para la zona una buena base de dataciones en estratigrafía de la que, hasta el momento, carecemos. La investigación sigue basándose, por lo tanto, en la datación relativa por tipología que en la mayoría de los casos, por desgracia, no parece ajustarse bien a las secuencias que se intuyen en este área.
Aportaciones del C-14 al mundo funerario carpetano: la necrópolis de Palomar de Pintado
Authors: Pereira Sieso Juan , Ruiz Taboada Arturo , Carrobles Santos Jesús
Published: October 2008

Se presentan en este trabajo los resultados de una serie de análisis de C-l4 realizados sobre huesos quemados procedentes de siete tumbas a partir de los cuales se pretende fijar el ámbito cronológico y fases de desarrollo de la necrópolis de Palomar de Pintado (Toledo) en el I milenio AC.
Yacimientos sin estratigrafía: Devesa do Rei, ¿un sitio cultual de la Prehistoria reciente y la Protohistoria de Galicia?
Authors: Aboal Fernández Roberto , Ayán Vila Xurxo M. , Criado Boado Felipe , Prieto Martínez Mª Pilar , Tabarés Domínguez Marta
Published: October 2008

Se estudia en este texto un yacimiento singular que ofrece importantes novedades, tanto por su reocupación discontinua en épocas distintas (con una secuencia amplia que cubre desde el Neolítico a la Edad del Hierro), como por su aparente funcionalidad ritual en todas ellas, y la posible identificación de una estructura funeraria de la Edad del Hierro de Galicia. Al mismo tiempo, este trabajo se plantea como caso de estudio que permite definir un procedimiento para reconstituir la secuencia y función de yacimientos abiertos de la Prehistoria Reciente de Galicia caracterizados por no presentar estratigrafía vertical. Este problema se solventa con el entrecruzamiento de diferentes técnicas de análisis basadas todas ellas en un registro de excavación de calidad que se sirve de análisis de cultura material, radiocarbónicos, distributivos, sedimentológicos y edafológicos.
El poblamiento de Europa en torno al límite Matuyama/Brunhes: su origen y su significado en la evolución humana
Authors: García Sánchez Eduardo
Published: October 2008

La revisión del registro inferopaleolítico europeo permite identificar tres episodios de poblamiento. El segundo de los mismos, datado entre OIS25/OIS24-OIS19/OIS18, ofrece industrias líticas y fósiles humanos que indican un posible origen esteasiático. Se ofrece una síntesis sobre este episodio de dispersión, relacionado con el reemplazo de faunas galerienses. Se analizan las posibles vías migratorias que siguió y los motivos que pudieron ocasionar su interrupción. También se plantean las relaciones filogenéticas de estas poblaciones, insertándolas en el marco evolutivo del Pleistoceno inferior y medio.
Valle de las Orquídeas: un yacimiento al aire libre del Pleistoceno Superior en la Sierra de Atapuerca (Burgos)
Authors: Mosquera Marina , Olle Andreu , Pérez-González Alfredo , Rodríguez Xose Pedro , Vaquero Manuel , Verges Josep María , Carbonell Eudald
Published: October 2008

El yacimiento del Valle de las Orquídeas constituye el primer lugar de ocupación al aire libre del Pleistoceno superior, localizado y excavado en la Sierra de Atapuerca. Contamos con dos dataciones de TL en la terra-rossa que forma la base de las secuencias estratigráficas estudiadas, las cuales arrojan una edad de 27.507 ± 2.295 años BP y 29.955 ± 2.319 años BP. El registro arqueológico se restringe a un conjunto lítico formado por 306 piezas. Este conjunto industrial es tecnológicamente homogéneo y se caracteriza por reflejar un substrato técnico típico del Paleolítico Medio, unido a ciertos rasgos del Paleolítico Superior. No obstante, es llamativa la configuración de útiles, que se aleja de las técnicas comúnmente utilizadas en ambos periodos.
Measured Wave Force Data on Offshore Platforms
Authors: Trasher L.W. , Aagard P.M.
Published: October 2008

Wave forces on vertical cylinders and wave profiles were measured with instruments on two oil production platforms in 30 ft (1954–58) and 100 ft (1960–53) of water, respectively, in the Gulf of Mexico. Waved data were recorded during a number of storms and for waves up to 40 ft in height. The Standard Oil Company of California designed, installed, and operated the measurement systems. Shell Development Company and Esso Production Research were financial participants in the projects; the U.S. Navy obtained these data as a data purchaser. These data have been proprietary but will soon be deposited in public archives. The purpose of this paper is to present the following background information that defines the wave force data being made available.Instrumentation.Raw data collected.Data processing steps.Location of archives.

INTRODUCTION

A Gulf of Mexico platform designer needed especially strong nerves during the period around 1950. He was designing drilling platforms for a multimillion dollar investment in the hurricane belt, but didn't know what would happen when those hurricane waves smashed into his platform. How big are such waves and what force do they exert? He had asked oceanographers and ocean construction men who offered calculation schemes but had little actual data on wave heights, wave forces, and tide levels that he could use for design. Recommended wave force values had a 4t to 1 spread. The only way the designer could decrease that spread was to place instruments in the ocean and take the measure of the waves. Designers in several oil companies took that step.

Table 1 lists some of the wave measurement projects that were started. Probably the construction and operation phases alone of those projects have cost the industry in excess of $2,000,000 and the data obtained are the most complete and accurate information available today for platform design.

This paper describes the information obtained in two of the listed projects, Wave Projects I and II, operated by Standard Oil Company of California, and announces the availability of the measured data.

THE INSTALLATIONS

The wave measurement installations were located in the Gulf of Mexico because the immediate design problem was there, and hurricanes occurred frequently to generate the large waves important to platform design. Figure 1 shows the locations of the two installations.

The first installation, Wave Project I, was completed in late summer 1954 on Chevron D platform, Bay Marchand in a water depth of about 30 feet. Data were obtained during five hurricanes and many smaller storms. After more than four years of operation, the instruments were dismantled at the end of the 1958 hurricane season.

A study of the data obtained during Wave Project I indicated that further measurements were warranted. To obtain data from larger wave in deeper water, a second installation, Wave Project II, was placed in operation in late summer of 1960 on a Chevron platform at South Timbalier Block 63. The water depth is about 100 feet.
Vessel Motion Line Control Through Anchor Springiness
Authors: Klotz J.A.
Published: October 2008

This paper concerns the catenary anchor lines used to anchor floating work vessels such as pipe laying barges, drilling vessels, and derrick barges. An anchored vessel in a sea-way behaves somewhat like a mass suspended between springs and acted upon by an oscillating force field. The mass will vibrate; the amplitude and frequency of this vibration depends upon the natural resonant frequency of the mass spring system, the frequency of the exciting force field, the size of the mass, the springiness of the springs, and damping. In a similar way a vessel in a sea-way will surge, pitch, and heave depending upon the wave periods, the size of the vessel, and the springiness of the anchor lines. For such a vessel, we do not have any control over the exciting force field, the size and frequency of the waves; nor do we have control over the mass of the vessel. But we can control the springiness of the anchoring system.

The analysis developed in this paper suggests that the springiness of an anchoring system can be controlled by changing the pretension in the anchoring system, by changing the weight of the anchor lines (through use of wire line or chain), and by using a compound anchor line consisting of an upper light weight, wire line section and a lower heavy weight, chain section.

The relationship between vessel motion and the anchor lines is shown by means of a specific example using an 880 ton vessel for which response functions have been previously published. The calculations illustrated in the paper suggest that the use of chain anchor lines results in less surge than use of wire lines and that inappropriate design of an anchor line consisting of wire and chain can lead to very large surge motions.

INTRODUCTION

Several years ago I visited many of the floating drilling vessels operating in the Gulf of Mexico in order to try to learn how the operators of these vessels adjusted their anchoring systems to keep the vessel on station and to minimize anchor line damage during storms. The things that I learned confused me. Some barge captains advocated slackening all lines before a storm other captains advocated tightening the lines. Some of the operators maintained that chain anchor lines were far superior to wire lines; others preferred wire.

In order to reduce this seeming chaos to a degree of rationality, I attempted to devise a mathematical analysis of vessel motions as they might be affected by the anchoring system. Then, I discovered a Rand Corp. memorandum written by J. J. Leendertse1 that appeared to cover some aspects of the situation. This present paper is based in part upon Leendertse's analysis.

As usual, when we attempt to apply formal mathematics to a complicated problem, we learn that many assumptions and simplifications are necessary to reduce the complexity of the mathematics to a point where some practical calculations can be made. This paper is no exception.
S7000: A New Horizon
Authors: Faldini Roberto
Published: October 2008

The Saipem 7000 (S7000) is now being upgraded to also perform deepwater pipeline installation. The upgrading works, to be completed in spring '99, will allow the S7000 to install pipelines from 4-inch to 32-inch diameter, in excess of 2000-m water depth and without affecting its unique lifting capability. The system will comprise the fabrication of a J-lay tower, 130 meters high, capable of handling quad-joints of 49-m length. The tower will house three conventional track-type tensioners, of 175 tonne capacity each, two working stations and a friction clamp system with 1000 tonnes holding capacity. For abandonment and recovery operations (A&R), a double capstan winch of 550 tonnes, will be installed on deck.

The system has been designed to allow for future upgrade up to 2000 tonnes pulling capacity and the use of an innovative electron beam welding system currently under development by Saipem/TWI[1].

In addition to installing the pipe-laying equipment on the S7000, a major marine upgrade is being undertaken. In particular two new, retractable, azimuth thrusters units will be added. The thrusters will be integrated within a completely new DP system of the latest generation, able to communicate with the most sophisticated surface and underwater reference systems. The increase of the propulsion system together with the existing station-keeping capability of the S7000 will enhance the operability in unfavorable environmental conditions. The first application of the S7000 in J-lay configuration will be in the Gulf of Mexico to install flowlines associated with the Exxon Diana Project.

This paper provides an overview on the advantages of the J-lay technology for deepwater pipeline installation and describes the vessel characteristics and the potential for further upgrading.

1.0 Introduction

S7000 is up to now the largest world SSCV, with its unique capability to lift structures weighing up to 7,000 tonnes (single crane mode) or 14,000 tonnes (twin crane mode) fully acting in class 3 Dynamic Positioning (DP) mode.

The S7000 is now being upgraded to also perform deepwater pipeline installation. The upgrading works, to be completed in spring '99, will allow the S7000 to install pipelines from 4-inch to 32-inch diameter, in excess of 2000-m water depth and without affecting its unique lifting capability.

2.0 Reason of the conversion

In the offshore industry the market request is sharply varying. Deep-water field development, TLP/Spar buoy/FPSO technology are accompanying and replacing the conventional construction methods (e.g. fixed platforms, GBS, trunklines/ flow-lines in relatively shallow water). Consequently offshore contractors face constantly decisions to meet or to anticipate the demands of the market.

Saipem has decided to reconsider deeply the S7000 future, and, performing his evaluation, has fixed the following targets:S7000 shall keep the actual heavy lifting capabilitiesS7000 shall enters in the ultra deep water-depth pipe-laying market

A major conversion to transform the SSCV also in J-lay vessel of trunk-lines/flow-lines has then been sanctioned.
Influence of Lay Barge Pipeline Laid Motions on a Deep Water Under Tension.
Authors: Brewer William V. , Dixon David A.
Published: October 2008

Tensioning is a prime requirement for laying deep-water pipelines. Of the several new or improved pipe laying methods which have been proposed, or even utilized, all require tensioning of the pipeline to minimize stress in the critical area. In these methods the use of a stinger is optional.

Dixon and Rutledge produced charts by which the minimum tension and angle of inclination could be determined for laying pipelines in intermediate and deep waters. The pipeline is freely suspended from the sea floor up to the stinger, or to the lay barge if no stinger is used. It takes a shape over its unsupported length which differs from a natural catenary at its ends due to the pipeline stiffness.

In the present work the authors have employed the same mathematical technique to study the sensitivity of a tensioned pipeline to lay barge motions, i.e., surge, heave and pitch. Two general trends emerge from the results, which are presented both in the form of graphs for several sizes of pipeline and for water depths up to 1,000 ft, and in the form of dimensionless charts. Surge, and to a lesser degree heave, is influential in shallow or intermediate water depths. Pitch becomes a critical parameter in deep waters where the tension is large.

The influence of a sloping rather than horizontal sea floor is also studied in this work. It is shown that for a practical range of slopes the prior analysis gives a satisfactory description of the configuration. However, additional curves, which have been provided, are required to make application of the previous results.

INTRODUCTION

As offshore production moves to everincreasing water depths there arises a growing demand for means of laying deeper and larger pipelines. Many new techniques have been proposed for meeting this demand; some have become practice while others are still in the development stages. Most of these methods have one important feature in common -- the use of tensioning in order to increase the unsupported length of pipeline and shorten (or eliminate) the conventional stinger. As operations move to deeper water it seems reasonable to expect the unsupported segment of the pipe to become much greater.

Recently, the Lavan pipeline, one of the world's deepest, longest and largest underwater pipelines,1 was laid in 290 ft of water using an abbreviated stinger and constant tensioning, Fig. lA. The same organization which laid this pipeline is currently building the world's largest pipe laying barge, which will be equipped with a means for applying tension, and will be capable of laying 48-in. pipe.2Another contractor, known for laying pipe from reels, found it advantageous to develop a torque converter by which a constant amount of tension could be maintained.3 It is important to point out that constant tensioning helps to reduce the influence of lay barge motions.

Still others have proposed total elimination of stingers. One such suggested technique was to lay the pipeline from the vertical derrick of a drilling vessel, similar to running drill pipe.4
Ocean Currents Offshore Northern Angola
Authors: Cooper Cortis K.
Published: October 2008

Large oil fields have recently been discovered in the deepwaters near the Congo River off northern Angola and Cabinda. Major facilities will soon follow. The metocean environment in this region is generally benign though little is known about ocean currents. Until 1990 there had only been a few synoptic measurements of currents but this is changing. Since 1990, Chevron has collected one year of moored current data, two years of wind data, three months of near-surface drifting buoy data, and two years of ADCP profiles from a drilling rig. All the measurements have been taken in roughly a 90-km square around the Congo Canyon, a deep east-west trench originating at the mouth of the Congo River. The paper shows a number of interesting processes that have important potential impact on deepwater drilling and facilities design and operation. These include 100 cm/s shelf waves, 150 cm/s river plume, 150 cm/s near-bottom jets, and turbidity currents. Some of the processes are no doubt observed in other low latitude sites, especially near large rivers.

Introduction

In the past two years, exploration in the deepwater off Northern Angola has discovered several billion barrels of oil in water depths greater then 400 m (Figure 1). Chevron is now designing major new facilities to produce these deepwater reserves. Metocean conditions are a key element in safely delineating and economically producing these frontier fields, as well as responding to oil spills.

In general, the wind and wave environment in the region is benign and well understood. Cardone1 et. al report on an extensive hindcast of winds and waves in the region and indicate 100-yr design maximum wave heights of 6–7 m, roughly a factor of five less then the North Sea or Gulf of Mexico. These waves reach the region as swell, having been generated by stronger winds hundreds of km to the south. Local winds are dominated by the SE Trades with a mean speed of 4 m/s although these are occasionally interrupted by brief squalls. A strong land-sea breeze is evident within about 30 km of the coast. Astronomical tides in the region are small with a mean elevation range of 1.2 m generating mild currents of less then 10 cm/s on the slope and outer shelf.

Much less is known about non-tidal currents in this region. Published work is limited to studies by Berrit2, Meulenbergh3, Wauthy4, and Eisma and Van Bennekom5. These studies involved synoptic CTD sections and limited synoptic current profiles within a few km of the Congo River mouth. Heezen6 et al. studied turbidity currents in the Congo Canyon and convincingly argued that they are responsible for the long deep trench at the mouth of the river (Figure 2).

The limited historical measurements show a stronginfluence from the Congo River, not surprising given that it has an average discharge of 40 k m3/s making it second only to the Amazon. Larger-scale oceanographic studies indicate that there are no strong permanent currents - the Benguela Current breaks away from the southern African coast well south of northern Angola.
Computing Soliton Currents from Synthetic Aperture Radar Images of the South China Sea
Authors: Lai David Y. , Ebbesmeyer Curtis C.
Published: October 2008

Solitons (solitary internal waves) are generated by the interaction between tides and bottom topography. Energetic solitons with vertical density displacements of over 100 m, accompanied by 3-plus knot surface currents, are often observed in the South China Sea. The strong episodic currents associated with these internal waves have significantly affected offshore oil operations.

A space-borne synthetic aperture radar (SAR) has the ability to provide all-weather imagery of ocean surface roughness. These images cover swaths of ~50 km at a spatial resolution of ~20 m. These lines are manifestations of surface roughness variations due to the modulation of short surface waves as they propagate through the spatially varying soliton surface currents.

An inversion model is developed to retrieve surface currents of solitons from SAR images. This data inversion is based on iterative fitting of SAR data to models of wave-current interaction, radar scattering and SAR imaging. The inversion model is applied to Space Shuttle SAR images of solitons in the South China Sea, and the surface currents thus retrieved are compared with in-situ current measurements. Due to the large area coverage and fine resolution, the ability to obtain accurate surface currents from SAR images makes them a cost-effective means for assessing soliton currents for offshore platform design.

Introduction

Solitons are generated by the interaction between tides and bottom topography. A packet of several solitons is typically generated at a time. The width of an individual soliton can range from 100 m in the New York Bight1 to several km in the Sulu Sea2. The length of a soliton can extend to more than 50 km1–6.

Extensive oceanographic surveys in the South China Sea near Pratas Reef southwest of Taiwan (Figure 1) revealed energetic solitons with vertical density displacements of over 100 m, accompanied by 3-plus knot near-surface currents5,6. Studies using a ray tracing model indicate that solitons in this area are generated between Batan and Sabtang Islands in the Luzon Strait, more than 500 km to the east of Pratas Reef5,6. After being generated at the source region, the solitons propagate westward towards the continental shelf. The presence of strong currents associated with these solitons has significantly affected offshore oil operations.
Genesis Risk Management Program
Authors: Visser Robert C.
Published: October 2008

An "expanded", qualitative risk management program was used for the design and construction of the Genesis Deepwater Spar located in the Gulf of Mexico. This program focused on the hazards associated with our project's unique technology/designs and the conventional high risk systems. The three key processes used were risk assessment, risk control and communication. The risk management program was beneficial in identifying and resolving potential technical, safety and environmental hazards, providing a mechanism for making cost effective decisions based on risk exposure, and facilitating earlier input to the design from all the diverse groups involved in the project. The paper will describe the scope, drivers, strategies, major processes used, major risk assessments conducted, lessons learned and benefits of the risk management program.

Introduction

The public, stockholders and corporate management are demanding improved safety and environmental performance. To support the demand for improved safety and environmental performance, formalized risk management processes have become more commonplace in the offshore oil industry. For example, within the last 7 years we have seen the implementation of the requirement for a Safety Case in the UK and other countries, and the issuance of API Recommended Practice 75 (RP75) Recommended Practices for the Development of a Safety and Environmental Management Program for Outer Continental Shelf Operations and Facilities.

Most risk management programs instituted for new shallow water offshore developments in the Gulf of Mexico, have followed API RP75, and deal mostly with production facility process hazards analysis, and fire and emergency planning.

New deepwater developments in the Gulf of Mexico are using new or limited-experience technology for which "common" industry design standards do not apply or are still under development. The lack of established standards, coupled with industry's limited experience with floating facilities like Spar's, TLP's, and deepwater risers, require expanding risk management beyond the standard process facilities hazard analysis to ensure that the unique hazards associated with the entire installation are identified, assessed, and mitigated in a cost effective manner.

This paper will describe a qualitative, fit-for-purpose risk management program used during the design and construction of the Genesis Project, a new Gulf of Mexico deepwater offshore producing installation. It will describe the scope, drivers, strategies, major processes used, major risk assessments conducted, lessons learned and benefits of the risk management program.
Managing a Safe and Efficient Startup for the Genesis Project
Authors: Williams Albert  J. , Sabrier J.J.
Published: October 2008

The Genesis Development Project was Chevron's first deepwater project and the world's first Drilling & Production SPAR. With very little precedence to guide the efforts of Genesis, new processes were continuously being developed to provide road maps for the unique challenges the project team faced. One of those unique challenges was managing facility hook-up, commissioning, and startup activities during the offshore phase of the project. Successful execution of these activities during the last stage of the project had a wide range of cost and schedule ramifications on the completion of the project.

This paper will review the commissioning and startup work plans, processes, and tools that were developed and implemented to enable the integration of these activities to be accomplished, without compromising safety, while minimizing adverse impacts to project cost and schedule.

Introduction

The Genesis Facility is located offshore Louisiana in Green Canyon Block 205, approximately 150 miles south of New Orleans. Water depth at GC 205 is 2650 feet. The facility consists of several major components:SPAR Hull - 122 feet diameter × 705 feet lengthMooring System - 14 linesTopsides Modules - Drilling, Utility, and Production Deck - Each 185 feet × 185 feetTopsides Production Facilities rated for 55,000 BOPD and 72 MMCFDQuarters Building - 110-man capacity permanent w/ 32-man temporaryOil & Gas Export Risers connected to departing PipelinesProduction Risers for 16 wells and 4 spare slots for future wellsRetrofitted Drilling RigRemote Operating Vehicle (ROV)

Considering the large scope of work activities to be completed offshore, key stakeholders were identified for coordinating the startup activities for each of the SPAR's major components. Startup of the hull and mooring systems, the drilling rig, and the ROV was coordinated by those Contractors who had primary responsibility for the design, construction, and operation of those systems. Startup of the Topsides production and utility systems was coordinated by Chevron.

Facility Startup Management Plan

The purpose of the Startup Management Plan was:to provide a common communication tool for all teams involved in startup;to provide guidance for the management of facility and personnel resources during execution of startup activities; and,to provide a framework for prioritizing startup activities to allow safe execution of all activities, within the schedule and budget constraints of the project.
HFAST: A Tool to Assess Human Error Potential in Operations
Authors: Noerager Jere A. , Danz-Reece Mary E. , Pennycook Wayne A.
Published: October 2008

HFAST (Human Factors Analysis Software Tool) is a self-help software tool used by operating sites to identify the potential for human error in the design, operation, and maintenance of site systems. Reduced error potential results in fewer errors in daily operations, leading to improved safety and more efficient operations. Through a process of consensus, the team rates diagnostic statements about the conditions at their site in as many as 14 general categories for improvement (e.g., field workplace design, procedures, training, communication structure). Based on these responses, the program produces a report that provides guiding principles for improving the design of systems and work processes to reduce the potential for human error. This paper describes the genesis and development of the tool, how the tool would be used by an operating site, and provides examples of site benefits from applying the tool.

Background

The petroleum industry has well-established safety and environmental policies that reflect a commitment to personnel safety and to protection of the environment and assets. However, the increasing complexity of industrial activities and rapidly evolving technologies have increased industry's safety management challenge. There is a need to build on and extend traditional practices to counter the increasing complexity of our operations.

Studies and incident investigations conducted within theoil industry and elsewhere clearly indicate that human error is a significant source of risk to safe and environmentally sound perations 1–9. Figure 1 indicates that human error is a contributor in 50-75% of incidents. In systems where a high degree of hardware redundancy minimizes the consequences of single system failures, human errors may comprise over 90% of the system failure probability 10.

Fig. 1 -- Addressing Human Error (Available in full paper)

A traditional emphasis on training, motivation, structured management systems, and discipline, coupled with hardware design improvements, has contributed to significant improvements to safety performance in industry. However, as technical components are becoming more reliable, the relative importance of human factors in achieving continued improvement is increasing. A recent survey of the literature 11 revealed that the estimated involvement of human error in the breakdown of hazardous technologies increased four-fold between the 1960s and the 1990s.

Many factors contribute to the potential for error. These factors may be out of the direct control of individuals or may not be obvious to individuals. Highly protected systems may also automatically recover from some adverse factors, hiding them from observation, unless there is an extreme error which results in a severe consequence. The potential for error is significant because it is influenced by the interaction of several factors, some of which may not be immediately obvious.
Supervisory Control Of Gas And Oil Production Offshore Australia
Authors: Carter Charles , Boxx Baxter
Published: October 2008

One of the first supervisory control systems to extensively employ integrated circuitry in an offshore application has been supplied by International Controls Corporation (ICC), Houston. The computer production control system will gather data from and control and monitor two offshore gas producing platforms in the Bass Straits between Australia and Tasmania from a control center in Sale, Australia. It is the first offshore installation of ICC's new, third generation S-70 Supervisory Control System. The highly flexible S-70 system can be used for oil as well as gas production and can be expanded to include up to 18 more platforms.

SYSTEM DESCRIPTION

The system consists of the Master Station at Sale and two Remote Terminal units (RTU's), one on each platform. The Master Station consists of the S-70 Computer Interface Unit (CIU) interfacing the RTU's with a Digital Equipment Corporation PDP-8/I digital computer. Both the 70/000-word computer and the S-70 CIU are of integrated circuit design. Also located at the Master Station is the operator console operated by the computer through the CIU.

Master Station Operation

The console consists of display units, indicators and pushbuttons with which the operator can observe the status of as well as control the operating platforms.

This system is of the continuous scan type. Unless the operator wishes to observe a particular type of data or initiate a control, the system will continuously interrogate the two offshore platforms for their production data and also for the condition of all status and alarms.

In the event an alarm occurs the computer will initiate a printout which will identify what the alarm is and where it occurred. The computer will also output to the console to sound an audible alarm and activate a flashing light. The lamp will identify the class of alarm (major or minor) and also on what platform the alarm occurred. If for some reason the computer cannot communicate with one of the RTU's, it will indicate with a light that that platform is not communicating. The CIU features a security check system which generates a security check code a message is being transmitted to the RTU. The RTU has the ability to check the incoming data with this security check code to determine if he data is valid. When the RTU transmits to the CIU it will generate a security check code which will be checked by the CIU. If the code does not check, the CIU will notify the computer and the computer will then ignore the data just received and also output to the console and turn on a light that says the data just received from a particular platform was invalid.

Not only does the console indicate to the operator that alarms exist the state of communications to the RTU's, but it also has a complete set of indicators that mimic the valve and pump conditions on the platform.

With the use of the pushbutton section of the operator's console, the operator can send control, or set-point commands to that RTU.
Dynamic Positioning Systems
Authors: Shneider W.P.
Published: October 2008

Dynamic positioning systems provide a highly versatile "anchoring" system for vessels that must remain on a given location out in the deep ocean. While no single system design can be universally used, general guidelines can be established to assist in the selection and the design of the various subsystems.

At the present time a dynamic positioning system has been designed and installed aboard a drilling vessel-The Glomar Challenger--and is currently being used with excellent success in water depths from 3,000 to 18,000 feet.

INTRODUCTION

As the interest and activity in the oceans increase, the need for "working platforms" that have the capability of being used in almost any water depth and at any geographical location has become significant. These working platforms require many peculiar characteristics but two of the more important ones are mobility and stationary stability; that is the vessel which forms the foundation of this working platform should have the capability of being rapidly moved from one location to another and once the desired location has been reached, it should have the capability of being essentially anchored at this location quickly and easily. At the present time, these characteristics cannot in general be obtained to the extent desired but, dynamic positioning systems can satisfy a major and necessary part of the requirements.

A dynamic positioning system uses the energy converted on board the vessel to provide the forces necessary to hold or "anchor" the vessel at a given location; no mechanical connection to the sea floor or other land masses are required. It should be noted that the mechanical connection considered here refers to constraining connections and not small lines that might be used to provide reference signals for the control system input since the necessity of having to set out anchors or make other mechanical connections to the sea floor is eliminated, the relative ease in which the vessel can be positioned at any given location as well as the ease in which the vessel can leave a location having once been maintained on "station" can be readily appreciated. Furthermore, in deep water (for example 18,000 feet) it is the only practical method of maintaining a given geographical position.

SYSTEM DESCRIPTION

A dynamic positioning system is composed of the following general subsystems:Postion measurement systemcontrollerVesselComparator

The subsystems are related as shown diagramatically in figure I. In essence, the positioning system can be considered as a closed-loop feedback servo or control system. In operation, a reference position (surface coordinates and vessel heading) is selected and provides the input to the control system. This input is compared to the measured position of the vessel and if a difference exists, an error signal is generated. This error signal is processed to provide the proper logic to the controller. The controller moves the vessel so as to reduce the error signal and when the error signal is zero, the measured position of the vessel coincides with the selected reference position.
Foinaven Super Duplex Materials Cracking Investigation
Authors: Taylor T.S. , Pendlington T. , Bird R.
Published: October 2008

Development of the BP Amoco Foinaven Field received a major setback when leaks were discovered during final commissioning of a subsea manifold. The problem was identified as hydrogen embrittlement, a phenomenon that can be created by the combined effects of the cathodic protection system (providing a source for hydrogen) and unacceptably high peak stresses applied to steels during the manufacturing, construction and installation phases. Although this mode of failure in conventional subsea materials was known, the limits of sensitivity of duplex stainless steels in a subsea environment were found not to be fully appreciated.

A BP Amoco Technology Team was formed who investigated the problem and then delivered a way forward that offered a long-term solution to the integrity of the subsea facilities in order to maintain a viable project. The challenge was to use the skills and experience of the team to review and adapt known and new technologies to engineer a "fit-for purpose" solution that integrated with, and met the rapid pace of the project.

Because a single solution to all of the scenarios generated by the cracking problem was not possible, it was necessary to identify and prove several options and then consider the merits of their application to every connector location. Sophisticated computer-modelling techniques, adapting known technology, laboratory testing of materials and full scale testing, were only part of the overall programme. Establishing an envelope of suitability for each option, and developing a justifiable case for each connector that accounted for all possible installation and operational start-up/shut-down cases, required the combined efforts of the multi-disciplined team with external specialist support. The investigative work carried out by the BP Amoco Technology Team has given the industry a fresh awareness regarding the use of these new materials for future subsea projects.

Introduction

The Foinaven Field development shown in Fig 1 utilizes dynamic Risers, Manifolds, Flowline Termination Assemblies (FTA), Pullheads, Subsea Xmas Tree Flowbases and a ipeline Umbilical Manifold (PLUM) which are installed on the seabed. These special items of equipment are all fitted with special forged steel connectors, similar to those fitted to the manifolds at the drill centres DC#1 and DC#2.

In addition to the 18 hubs on the two manifolds, there are a further 163 super duplex hubs in a full 24 well development which connect the various items of seabed equipment. These large, complex forgings were manufactured from "Super Duplex" Zeron 100 stainless steel because of its superior resistance to corrosion from the produced fluids. During routine pressure testing of various piping/flowline circuits some 6 months after the DC#1 manifold had been placed on the seabed, leaks were discovered in two of these special forged connectors (see Fig 2).

Fig 2 DMaC Super Duplex Hub Forging with Welded Pipe Connections (Available in full paper)
Steel Catenary Riser Configurations for North Sea Field Developments
Authors: Karunakaran Daniel , Lund Kjell M. , Nordsve Nils T.
Published: October 2008

Free hanging metal risers have become an important alternative to flexible risers for oil and gas field developments. These risers also have a potential benefit when used in high temperature and high-pressure applications.

This paper presents a summary of the work performed to establish Steel Catenary Riser (SCR) concepts for two fields in North Sea. They are: Statfjord C, a gravity based concrete platform located on the Norwegian continental shelf in a water depth of approximately 145 m and Heidrun, with a concrete TLP at a water depth of 345 m.

These developed configurations fulfil both the Ultimate Limit State (ULS) conditions and fatigue due to first order wave action and due to vortex induced vibrations. Also, as shown in this paper, the Fatigue Limit State (FLS) governs the global configuration of the SCR concept.

In order to achieve a confident design, several design aspects have been studied in detail:First order wave loadingVortex Induced Vibration (VIV)Diffraction effects (from the large volume structure)Riser/Soil interactionFatigue capacity

Introduction

A number of research and development projects are currently evaluating the applicability of the SCR concept to floating production systems mainly in deep-water environments (e.g. Karunakaran et al. (1996), Hatton et al. (1998)). However, as shown in this paper, the SCR concept could be an attractive alternative also for tie-in of pipelines to fixed platform structures, like Statfjord C, see Figure 1.

Even in the absence of top-end motions (as for floating production units), the design challenges for a SCR concept for this application are significant. Due to the relatively shallow water and quite severe wave and current environment, the riser is subject to large hydrodynamic loading causing extensive dynamic behavior.

For the Heidrun TLP shown in Figure 2, the design challenge for the metal risers is due to the riser dynamics from wave loading and the platform motions. Furthermore, for this concept the diffraction effects proved to be a key factor for fatigue response.

In this paper the developed SCR configurations for both these fields are discussed along with the key issues governing the design of such riser concepts.

Figure 1 Statfjord C and riser geometry (Available in full paper)

Figure 2 Heidru TLP (Avalaible in full paper)
Tomographic Updating for Residual Velocities
Authors: Thorson J. , Bednar J. Bee , Vinson L.
Published: October 2008

The depth mismatch of events at different offsets on a collection of common image gathers (CIGs) is minimized by backprojection of slowness values in a grid. Rather than laboriously picking events on given CIGs, (v,t) pairs are used to calculate necessary arrival times and depths. For each iteration of the prestack migration process, the previous velocity field is used to calculate ray paths, change in path length, slowness, and opening angles. Back-projection is constrained by (a) smoothing slowness laterally and vertically to stabilize the minimization, and (b) holding slowness constant in certain regions (e.g. salt bodies). The utility of the approach is shown through application to both finite-difference synthetic and real data in two and three dimensions.

Introduction

Figure 1 shows the migration paths for two different offset traces that make contributions to the CIG at a given surface image point.

To obtain a linearized relationship between the change indepth ?z of an image point of the CIG and the change in path length ?l of the ray note that with reference to Figure 2(Mathematical equations) (Available in full paper)

Fig. 1-Depth section showing raypaths for near and far offsets and indicating depth differences at z0 and zh and known dip ?. (Available in full paper)