bluuebunny/crossref_metadata_2025_split huggingface dataset:
Jet Streams of the Tropical Atlantic: Observing and Forecasting the North Brazil Current Retroflection
Authors: Christensen Michael , Srinivasan Ashwanth , Nelson Jill , Sharma Neha , Brickley Peter 
Published: May 2013

Abstract
The North Brazil Current (NBC) forms an inter-hemispheric connection for South Atlantic tropical water into the Northern Hemisphere and is the dominant circulation feature in the western tropical Atlantic. The NBC separates from the South American coastline near 6–8°N and retroflects to feed the North Equatorial Counter Current (NECC). The NBC Retroflection (NBCR) typically pinches off to form a closed circulation and then sheds an anticyclonic eddy, known as an NBC ring, five to eight times annually. The NBCR undergoes a seasonal increase in transport during boreal summer and fall, advancing well to the northwest (up to 10°N) with a corresponding shift in the position of ring generation. The strong currents of the NBCR and its rings adversely impact deepwater oil exploration lease blocks throughout the region. Deepwater exploration is expanding throughout the region, but limited metocean observational data poses a major challenge for predicting the impact of the circulation on drilling operations. We present characteristic patterns of the NBC and the NBCR derived from 11 years (2002–2012) of remotely-sensed synoptic observations (color, temperature and height) and satellite-tracked drifting buoys. Ring radii range from 80 to 320 km (40 – 170 n.mi.) and exhibit azimuthal surface currents from 70 to 200 cm s-1 (1.3–3.8 knots). We describe the local impact of complete NBCR ring-shedding cycles. A state-of-the art 1/24th degree resolution HYbrid Coordinate Ocean Model (HYCOM) was configured and tuned for the region. The domain and resolution were chosen to capture the NBC from its origin in the Atlantic and nested within the global HYCOM model. A hindcast scenario of the observations in 2011–2012 is presented with emphasis on the predictability horizon of the NBC and associated circulation.

Introduction
The North Brazil Current (NBC) is a warm, northward-flowing western boundary current that dominates the circulation of the western tropical Atlantic. The NBC originates in the southern hemisphere from the westward- flowing South Equatorial Current (SEC). It flows along the South American continental slope to latitudes near 6°–8° where it separates from the coast as the North Brazil Current Retroflection (NBCR) and ultimately joins the eastward-flowing North Equatorial Counter Current (NECC). The NBC varies from a shallow, coastally trapped flow in the spring, with nearly half of its transport confined over the Brazilian shelf, to a broader, deeper-reaching flow in the fall [Johns et al., 1998]. Minimum and maximum transport occurs in boreal spring and late summer/fall, respectively, with most of the seasonal transport variation confined to the upper 300 m [Johns et al., 1998]. During the months of maximum transport, the NBC and NBCR current typically exceed &gt;3.0 knots at the surface with strong flow present to depths of at least 150 m.
How New Data Acquisition Technique Can Complement Full Waveform Inversion and Lead To Improved Subsalt Imaging
Authors: Moldoveanu Nick , Vigh Denes 
Published: May 2013

Abstract
Full Waveform Inversion (FWI) has become a new tool in recent practice for subsurface velocity model updating. When using FWI, the common scheme was to use data sets which have relatively large offsets up to 8 km or more and frequencies as low as 2.8 Hz considering surface seismic acquisition. In terms of the marine environment, Wide Azimuth towed streamer (WAZ) or Ocean Bottom Cable (OBC) data collection provide the above mentioned specifications. Recent advances in acquiring data such as the dual coil method offer significant improvements in characteristics over WAZ and OBC such as better illumination, lower frequencies, and longer offsets which allow the FWI to more accurately determine the velocity field. In this paper, the data set that we input to FWI is a result of dual-coil acquisition where the maximum offset is up to 14300 m with full azimuth distribution. In order to approximate the observed data, the acoustic inversion incorporates anisotropy, in the finite difference propagators and uses the true source and receiver depth. Our results demonstrate that FWI can be used for velocity update with the long offsets and low frequencies provided by the above described dual coil seismic acquisition. In particular, the shallow section of the model can be significantly enhanced by using FWI which can result in an improved overall depth image. Furthermore, lower frequencies and longer offsets mitigate the sensitivity of inversion to the initial velocity model by enabling FWI to update the low wave-number component of the velocity model. Finally, we show the reverse time migration depth image improvements by using the FWI developed velocity field versus that one from the ray-based methodology.

Introduction
Over the past few years, 3D FWI with the acoustic wave equation has been applied to real datasets in marine (Plessix, 2009, Sirgue at al., 2010, Vigh et al., 2010, 2011) and in land (Plessix, 2010) environments. These results have demonstrated that FWI can be used to update the velocity if the acquired data contain low enough frequencies and long enough offsets. In particular, the shallow section of the model can be significantly enhanced by using full-waveform inversion which can result in a more improved overall depth image. One of difficulties with FWI is the convergence to the local minima that makes the technique very sensitive to the starting velocity model especially when 3D is considered. To mitigate the sensitivity to the initial velocity field, low frequencies and long offsets are required (Bunks et al., 1995, Pratt, 1999) which enables FWI to update the low-frequency component of the velocity model.
Driving Innovation Through Collaboration in the Rig Marked
Authors: Eikill Geir Ove , Attramadal Anders Kristian 
Published: May 2013

Abstract
The Norwegian Continental Shelf (NCS) is being revitalized, with new discoveries and production replacement. The NCS rig market is characterised by an ageing rig fleet, where 2/3 of mobile offshore drilling units (MODUs) are 25 years or older. Additionally there are perceived high entry barriers, high cost levels, constrained rig capacities and a lack of fit for purpose rigs for mid-water production drilling and completion as the market is dominated by deep-water rigs optimised for exploration drilling.
An aggressive drainage philosophy from a high number of wells is required for a sustainable production profile on the NCS. Thus, a new rig category strategy has been developed to ensure fit for purpose rigs to achieve higher operation efficiency. Additionally a new procurement model has been a key to achieve industry collaboration in the rig design process.
With 40 years experience on the NCS we are confident of what tools we need. The main goal is to implement the category strategy to secure fit for purpose tools for our operations. We have among others had a good start with the mid-water Cat D semi-submersible rig, and a shallow-water Cat J jack-up rig for efficient year around drilling, completion and heavy intervention operations. Ambition for these " workhorse rigs" is 20% more cost efficient production drilling activities on the existing mature fields compared with present rig fleet.
Early involvement and collaboration with the industry has been key to unlocking experiences from different drilling contractors and yards. Key success factors have been to facilitate experience gained from the previous 6th generation MODU new builds into the new safe and cost efficient production drilling concepts. The Cat J units are currently in a tender process, while the first four Cat D units are under construction in Korea. One key take away so far is that competition in all levels of the product is a more important cost driver than the requirements, specifications and equipment.
A Risk Based Approach To Managing The Integrity Of Aging Fpso Topsides
Authors: Kemp Douglas Alexander 
Published: May 2013

Abstract
When an aging oil tanker is converted into a floating production facility, unexpected challenges may arise when designing, installing, and maintaining topside process facilities.
The oil and gas and marine industries have differing design practices, design codes, quality standards, and maintenance philosophies. These differences can result in underlying integrity issues for which there is little significant industry guidance or experience available. Using a converted tanker in a regular, more frequent loading and offloading cycle than was originally intended can introduce structural integrity issues to the process and marine piping systems as well. Infrastructure of varying age coupled with topside modules and piping systems designed according to fixed platform design code and experience also add to the integrity management challenges for such assets. When adopting risk-based integrity management on floating production storage and offloading (FPSO) process systems, these challenges can affect risk-based inspection methodology selection, the level to which it can be practicably applied, and failure mode determination.
This paper describes Hess Corporation's (Hess) processes, practices, and risk application in the development of an integrity management system (IMS) for an aging FPSO topside located in West Africa.

Introduction
Hess is an exploration and production company that operates both floating and fixed offshore assets in the North Sea, West Africa, and Southeast Asia. Hess assumed operation of the Sendje Ceiba FPSO facility in 2006 to support the depletion of the Ceiba and Okume fields, located in Block G of the Rio Muni Basin, Equatorial Guinea, West Africa.
Hess' corporate integrity philosophy has evolved from US PSM regulation and ASME/API practices, UK safety case and performance standard culture, and the experience gained from operating and maintaining assets in various theaters throughout the world.
Eddy Current-Caused Platform Vibration and Correction
Authors: Buescher Frank J , Kallaby Joe , Campo Juan J 
Published: May 2013

Abstract
The fixed-base steel platform experienced unusual deck vibrations soon after installation during Eddy current episodes. The approximate 70 cycles/minute oscillation of the deck resulted in the temporary evacuation of personnel. The platform is a skirt-piled structure in 430 ft. of water. The paper will present analyses performed, current measurement methods employed, motion detection devices utilized and corrective measures investigated and selected.
The identification of the cause of the vibrations will help in understanding and preventing future occurrences. The corrective measures investigated and utilized will assist operators encountering similar behavior on existing facilities.
Eddy currents are capable of producing vibrations on fixed-based platforms when the platform geometry is prone to excitation from steady high currents due to the shedding of vortices from submerged elements. Current-created vortices shed from platform members and appurtenances created a resonant condition on the platform J-tubes. The J-tubes fundamental period of vibration matched one of the deck's vibration modes, causing the 70 cycles/minute motion.
This type of platform behavior resulting from the influence of high Eddy currents was essentially new to the industry and is not found in the literature. Field data, results of computer analyses, field measurements and details of corrective measures investigated and selected are included in the paper. Dynamic, fatigue and vortex shedding analyses were performed utilizing commercial and proprietary software. Computational Fluid Dynamics simulations were also employed. Mass dampers, although not employed, were investigated and devices designed for the platform.
The paper provides critical new technical knowledge to resolve an important problem:Identification of platform geometry prone to Eddy current excitation.Analytical methods best suited to solving the problem.Corrective methods utilized to arrest the motion.Other corrective methods investigated but not utilized on this platform.Current measuring and motion detection devices utilized to obtain applicable data.
Fiber-Based Methane Leak Detection
Authors: Mcfadden Jim 
Published: May 2013

Abstract

Fiber-based Methane Leak Detection System
The current focus in the post-Macondo era is the need to make the offshore work environment safe. The use of a fiber-based backbone to perform a number of functions in an installation with the potential of an explosive atmosphere has significant potential. Currently the novel fiber backbone has the capability to provide three basic functions: area and equipment lighting, distributed remote temperature sensing, and distributed remote methane sensing. The application of fiber optics for lighting and distributed sensing is a mature concept. It is the use of fiber optics for methane detection that is novel.
Methane sensing utilizing discrete passive sensors connected to a central sensing unit with fiber optic cable. The system utilizes a low power (10mW) diode laser in conjunction with a distributed fiber network and a series of ruggedized sensor modules. It is largely unaffected by common environmental conditions which can cause erroneous readings with many other sensor types including high humidity, anaerobic conditions, and the presence of other non-target gases. The system is tolerant of dust contamination, and fully functioning at signal losses of up to 90%. It can be configured as a distributed network with hundreds of sensing points at distances of up to 20 km from a central control unit. Methane levels from 0.5 to 100% can be accurately measured. Standard communication grade fiber cable is utilized. Unlike conventional methane detection systems currently employed, this system does not require calibration at the remote sensor. Various alarm schemes can be configured to look for rising methane levels, over-limit conditions, as well as breaks in the sensing fiber.
This paper describes the concepts and provides examples of real-world implementations of how this technology can provide for safe offshore working conditions.
Recent Trends in the Analysis and Design of Offshore Platforms in Seismic Regions
Authors: Puskar Frank , Ku Albert , Litton Richard 
Published: May 2013

Abstract
The growth of the offshore industry into newer regions - including seismic regions - requires a detailed understanding of the earthquake design of offshore platforms. Guidance is provided in ISO 19901-2, " Petroleum and natural gas industries, Specific requirements for offshore structures, Seismic design procedures and criteria." This was adopted almost in it's entirely by API in 2013 in the form of API RP2EQ, " Seismic Design Procedures and Criteria for Offshore Structures." This paper provides supplemental information to these ISO and API standards with the intent to provide additional guidance to engineers analyzing and designing platforms in earthquake regions. The guidance is based on practical application of these standards over the past few years on platforms located in different worldwide regions. Issues discussed include: historical development of seismic guidelines; the importance of ductility in a platform design; Pushover and Time History analysis procedures; definitions of platform collapse; and, pre-planning for post-earthquake actions.

Historical Development of Offshore Platform Seismic Guidelines
Offshore platforms have been designed and installed in seismic regions since the 1960s when the first platforms were installed offshore California. These early structures used the onshore seismic design practice contained in the Uniform Building Code (UBC) of the time. The first specific guidance for seismic design for offshore platforms appeared in the API RP 2A (RP2A)" Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms," 1st Edition published in October 1969 and contained specific reference to the UBC including the calculation of an equivalent lateral seismic design load using a special structure design factor for offshore platforms. However, the guidance was limited to only a half page of the sixteen page document. The API RP 2A 3rd Edition issued in January 1972 maintained the UBC guidance but was the first to specifically also mention dynamic analysis as an option, although the guidance was limited to a small paragraph.
A General Optimization Framework for the Routing of Oceangoing Vessels in the Petroleum Industry
Authors: Pelton Jimmie 
Published: May 2013

Abstract
Optimal routing problems have a rich history and a broad contextual base, ranging from the canonical and well developed network flow problems of linear programming to kinetic models and heuristics based on empirical data. The optimal routing problem can now be readily informed by widely available meteorological forecast data. While these data support both iterative and purely analytical methods, the underlying problems are by their nature nonlinear and pose the challenges of indeterminate optimality and limited applicability associated with nonlinear methods. This paper presents a framework for addressing a broad range of routing optimization problems leveraging gridded meteorological data as a common input. It provides a structure that treats these problems as linear programming formulations, liquidating the nonlinear calculations a priori in the creation of cost matrices. The resulting structure allows rapid reformulation of problem statements and subscribes to a broad and well established body of supporting algorithms.

Introduction
Global meteorology and oceanography (met-oc) model data are presently sufficient in coverage, resolution, and availability to support dynamic optimal routing predictions worldwide. While the results of such predictions should be weighed with George Box's famous caution that " All models are wrong but some are useful", these data are continuously improving in accuracy and form the only consistent and convenient basis for route optimization over large areas. Treatments of the optimal routing abound, spanning from the empirically-derived " isochrones" of James (James, 1957) to the purely analytical calculus of variations as applied by Hamilton and others (Hamilton, 1961). While many practical treatments aim for rigor within well-defined contexts and address particular challenges stemming from the innate nonlinearity of met-oc data and its geographical frame, the following proposes a methodology that can be applied to a wide range of met-oc based problems with relative ease, a reasonable assurance of accuracy, and a modest degree of calculation. The formulation is based upon geographically gridded and time-tagged met-oc data, for illustration here zonal surface current velocity, meridional surface current velocity, and sea swell height and period. Other geographically-referenced data, such as bathymetry contours, environmental protection boundaries, territorial waters, or navigation hazards, are accommodated in the structure as constraints upon the variables to be optimized.
RPSEA Riser Technologies and Strategies
Authors: Head William Joseph , Pappas James Marcus 
Published: May 2013

Abstract
The results of our riser project studies will allow industry to improve its ability to safely drill or produce hydrocarbon resources from the ultra-deepwater environments around the world, at lower costs, and more reliably than currently available methods. They include the use of lower weight composite high pressure drilling risers, the development of shrink-fit connections for high pressure production risers, a conceptual study on risers for high-motion vessels in 10,000-foot water depths (fwd), as well as a qualification program for two different flexible fiber-reinforced high pressure production risers capable for use in 10,000 fwd. In general, RPSEA's efforts are aimed to push the technology well beyond their current capabilities to surpass 15,000 psig at high temperatures.
Bayesian Inversion of Heterogeneous Media: Introducing the Next Generation of Integrated Studies for Offshore Site Investigations
Authors: Medina-Cetina Zenon , Kang Jun Wong , Esmailzadeh Saba , Kallivokas Loukas 
Published: May 2013

Abstract
This paper introduces a new methodology for addressing the probabilistic determination of geomorphological features and of the material properties, which allows for its uncertainty quantification and the spatial correlation across parameters when information from different geophysical methods is merged. The proposed approach departs from traditional stratigraphic characterizations advancing the possibility of establishing a systematic and reproducible approach that can reduce the subjectiveness and the unnecessary costs related to over conservative estimates for hazard assessment and structural design. A synthetic case study for a 1D heterogeneous media is formulated to illustrate the use of the probabilistic calibration method and of Tarantola's operators, when applied to two geophysical techniques used at the same site. Results show probability distributions of the location of the transition between layers, of the material properties, and of the collaborative operators for merging information content from different geophysical methods.
Shuttle Tankers in the Oil Export of Cascade and Chinook Fields
Authors: Souza Elisa , Matos Sergio , Souza Marco , Mastrangelo Carlos Ferraz , Barros Dalmo Gripp , Daniel Jeremiah , Hibbert O'Neil 
Published: May 2013

Abstract
This paper is based on the work performed during the offloading operations in the Cascade and Chinook fields in Ultra Deep Waters of the U.S. Gulf of Mexico. It addresses the tandem offloading from the first FPSO to operate in the Ultra Deep Waters of the U.S. Gulf of Mexico to the first use of purpose-built Jones Act shuttle tankers to perform such operations in the U.S. waters.
The paper also covers the experience of the shuttle tankers crew on offloading operations as well as the proved performance of the vessels equipment.
The main technical contributions of the work presented in the paper are associated with the unique features of the first use of purpose-built Jones Act shuttle tankers in the Gulf of Mexico, such as: Bow Loading System (BLS); Green Line System; and Differential Absolute and Relative Positioning Sensor (DARPS).
The successful use of tandem offloadings from the FPSO to shuttle tankers at Cascade and Chinook fields confirms the adequacy of such solution in the U.S. Gulf of Mexico, and opens the possibility for growth in the Jones Act shuttle tanker fleet.

Introduction
Produced oil from the Cascade and Chinook (C&C) fields is being successfully and safely exported from the Floating Production Storage and Offloading vessel BW Pioneer (FPSO) to shore via Shuttle Tankers (ST). Petrobras pioneered the tandem offloading concept between FPSO and ST in Ultra Deep waters of the U.S. Gulf of Mexico (USGoM).
Petrobras executed the first C&C offloading operation on June 8th, 2012, which was the first tandem offloading operation conducted in the USGoM where produced oil was transferred from a FPSO to a ST via tandem offloading system specifically designed for use over the entire duration of the FPSO operation at C&C fields.
This paper describes key aspects associated with the use of STs for oil export in the USGoM, including information on the main characteristics of the STs and offloading operation. The content of this paper includes technical contributions associated with the unique features of the STs, as well as its impact on future USGoM Ultra Deep water field development.