bluuebunny/crossref_metadata_2025 huggingface dataset:
Case Study: Heating Offshore Production Tubing Electrically for Crudes that Have Wax Issues
Authors: Parman David G. , Marron Andrew James
Published: May 2013

Wax buildup that would restrict the flow of the oil from the reservoir to the offshore platform was expected in several wells offshore New Zealand. Alternatives such as hot oiling, scraping and chemical injection were rejected, since electric downhole heating was the most efficient, economical, reliable, and environmentally friendly solution. The use of a unique, skin-effect electrical heat tracing system inside the production tubing was selected as the most efficient and cost-effective method. This heat tracing system involved a sealed coiled tubing, with an internal cable and filled with di-electric oil, that was installed in the production tubing. This created a skin-effect heater with maximum heat transfer and also ease of installation.

The use of heaters inside the production tubing provide a more effective and efficient system for flow assurance than external heaters on the tubing would. The heaters, called skin-effect heat tracers, covered the length from the reservoir to the topsides, some 1,700–2,000 meters (5,577–6,562 ft.). The reservoir temperature was only 50 0C (122 0F) and the crude had a Wax Appearance Temperature of 48 oC (118.4 0F), so even minor cooling could potentially cause wax buildup problems. Typically well flows were heated effectively during operations to ensure that the tubing head temperatures were 60-65 0C (140- 149 0 F) so that wax was never deposited on the tubing. The heaters can easily be adjusted at the surface to provide the required heat under varying operating conditions.

Skin-effect heating is an efficient, reliable, and easily adjustable method to prevent flow assurance issues that can be retrofitted to existing offshore or onshore wells The total system is very space efficient both downhole and on the platform.

Some of the conclusions include that the flow assurance issues of wax buildup and the resulting restricted oil flow were resolved in an economical and efficient manner. Also, this unique, first application of skin-effect heat tracing downhole for a deep offshore well provided reliability and economic returns on investment. Finally, this method can also be used to prevent other flow assurance issues such as viscous oils and to prevent hydrate formation.
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

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 >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

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

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

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

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

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

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

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

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

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

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.
Subsea Uninterruptible Power Supplies (UPS) for Local Holdup of Magnetic Levitating Bearings in Subsea Production Hardware
Authors: White Derek Alan , Greig Alex , Grob Harald
Published: May 2013

The use of batteries subsea has historically been limited to powering autonomous instrumentation for oceanographic applications with power capacities typically limited to less than a few hundred watt-hours. Over the past decade, engineering design and technology advances in subsea applications have led to an increased focus on battery technology, including increased capacity. In particular, the growth of the autonomous underwater vehicle (AUV) market in the early 2000's lead to regular use of batteries subsea with capacities of up to tens of kilowatt-hours (kWhr).

In order to enhance production and maximize reliability of offshore fields, focus has increased on placing traditional terrestrial equipment subsea and incorporating electrically powered process equipment. Some of these applications have led to the deployment of large battery and UPS modules for subsea deployment. Notable applications include the recent development of 165kWhr battery modules for the Marine Well Containment Company (MWCC) to allow subsea pumping of dispersant from bladder fields to an uncontrolled hydrocarbon leak, and uninterruptible power supplies that have been marinized for holdup of critical equipment on compressors being qualified now for installation on the Ormen Lange oilfield.

This paper focuses on a concept system being developed and qualified for military applications, similar to the MWCC battery system. The focus is on a marinized pressure compensated battery module of 150kWhr, which can be daisy-chained or arranged in a hub configuration for up to 1.5MWhr of holdup capacity. This paper details original analysis on the application of these battery power modules to provide a UPS for dedicated use with magnetic levitating bearings common on subsea compressors and motors on subsea production systems. By providing a localized UPS system to the magnetic levitating bearing controllers, it is possible to provide a redundant power source, mitigating risk from failure of the primary subsea power supply. Coast down times for the magnetic bearings typically take just a few minutes and fit well within the voltage, current, and power supply levels of the UPS design described in this paper. The distributed UPS system design discussed herein utilizes a modular design. The modules discussed can be configured to allow for expansion and enhanced redundancy to be integrated subsea without the need for a unique qualification program.

This paper discusses potential applications of the UPS within subsea production equipment, including interface points, recovery, discharging, charging, and monitoring.
Integrated Use of 3D Seismic, Multibeam Sonar, and ROV To Confirm Deepwater Benthic Communities and Archeological Sites in the Gulf of Mexico
Authors: Irion Jack , Shedd William W.
Published: May 2013

Two of BOEM's regulatory responsibilities are the protection of chemosynthetic and coral communities, and archeological sites from impacts from the agency's permitted activities. BOEM geoscientists have used 3-D seismic data since 1998 to identify over 19,000 amplitude anomalies in the deep water GOM that are interpreted to be hard substrates suitable for benthic organisms. Where deep ocean currents are adequate to wash the fine hemipelagic mud off these carbonates, the latter becomes a clean, suitable substrate for benthic organisms. Unfortunately, 3-D seismic has a vertical sample of around 30 feet and cannot directly provide information about the cleanliness of the substrate. High resolution multibeam sonar does not penetrate more than a centimeter below the surface, so areas of high backscatter are indicative of clean substrate. Multibeam surveys in the GOM by the NOAA ship RV Okeanos Explorer in 2011 and 2012 not only identified those portions of BOEM's 3-D anomalies that were clean carbonate, but they also identified over 300 water column backscatter anomalies indicative of active seepage of gas from the seafloor, confirming those 3-D anomalies as active seep sites. The 2012 cruise had an ROV aboard to do direct video investigation of these sites.

BOEM relies on industry-conducted high resolution sidescan sonar surveys that are shot to accompany an operator's exploration or development plans. Hundreds of sonar targets have been reported to BOEM by industry as potential shipwreck targets and, so long as industry is able to avoid physically impacting these sites, they may remain as unidentified acoustic anomalies. In 2012, NOAA's research ship Okeanos Explorer equipped with the Little Hercules ROV provided BOEM the opportunity to visually inspect five of these targets to determine their historical significance. All of the sites proved to be historic remains, but one was discovered to be a well preserved early 19th century armed sailing ship. Because of Okeanos Explorer's unique capability to broadcast high definition video via Internet2 to shore-based command centers (as well as over a standard internet connection), the investigation was conducted remotely by a team of archaeologists from across the country and was shared real-time around the world.
Towards Persistent Real-Time Autonomous Surveillance and Mapping of Surface Hydrocarbons
Authors: Vuorenkoski Anni K , Thomas Jesse C , Dalgleish Fraser R , Ouyang Bing , Carragher Peter D
Published: May 2013

This paper describes results and findings from a recent two month robotic surface seep monitoring mission in the north-eastern Gulf of Mexico. The studied sites are at Mississippi Canyon salt domes and mud volcanoes which have well known natural seepage, resulting in the existence of regular but short-lived surface oil slicks. Effective real-time monitoring of such phenomenon requires new in situ technology that is capable of long term persistent surveillance and robust autonomous hydrocarbon detection. The core component of this mission was the Wave Glider autonomous marine vehicle integrated with a multi-channel optical sensor payload and weather sensing instrumentation package. A statistical process control (SPC) based automatic hydrocarbon event detection algorithm was also further developed and demonstrated during the mission.

The paper also includes results describing the Wave Glider multi-sensor signatures to known hydrocarbon concentrations in typical marine elastic and inelastic scattering background environments. A series of experiments were independently conducted in both controlled laboratory conditions and also in a controlled spill facility, with ground truth spectrofluorometry and water sampling analytics results also being obtained. The event detection algorithmic approach was tested and refined using data from these sets of experiments, as well as the data acquired during the field mission. The algorithm was executed with near real-time Wave Glider data during the second month of the mission and results demonstrate that robust real-time surface hydrocarbon detection is possible and can be used to reconfigure the Wave Glider behavior, converting from a surveillance mode to a survey or mapping mode in order to determine the boundaries and origin of the identified surface slicks. To further corroborate with the in situ results, coincident SAR imagery collects were made at certain phases of the mission to assist with the analysis of the multi-sensor signatures, slick lifetime and spatial extent as derived by the Wave Glider measurements.
Relationships Between Oil Seeps and Seabed Morphologies
Authors: Cauquil Eric Charles , Jatiault Romain , Dhont Damien
Published: May 2013

Owing to the permanence of a great quantity of natural oil seepages and to the variety of structures in the seafloor, the deep offshore of the Angolan margin is one of the most favorable areas in the world allowing a better understanding of the relationships between surface seepages and seabed morphologies. The analysis of radar satellite images at different dates shows that oil seeps form patterns of flower structures. Each petal of an isolated flower structure represents a single seepage, all of them converging toward an impact point at the sea surface that can be associated to an emission point or vent in the seafloor. The rising speed of the oil in a water column of 1800 m is 10 cm/s, which corresponds to a lateral drift of about 1000 m. Active vents in the seafloor correspond to submarine mounds and clustered pockmarks, whereas unit or single pockmarks are not associated to the leaking of oil.

Introduction

Synthetic aperture radar (SAR) sensors constitute a powerful tool to detect hydrocarbons at the sea surface because of the sensitivity of the microwave signal to the surface roughness (e.g., Williams and Lawrence, 2002; Zatyagalova et al., 2007). Oil slicks dampen the waves at the ocean surface and reduce the intensity of the backscattered radar signal, creating dark patches in the image. The distinction between natural oil seeps and look-alikes such as pollution and natural film slicks may be tricky with the sole use of SAR images. The categorization of oil slicks is merely based on the experience of the photo-interpreter how is able to recognize morphological and/or key features associated with either natural or man-made leakages.

The relationships between surface seepages and the emission point on the seabed is not well constrained because of the difficulty in recognizing (i) the precise location of the impact points of the oil at the sea surface, (ii) the distinction between deep-sea active and non-active vents, and (iii) the lateral drifting of the " oil plume" in the water column.

We focused our study on deep offshore of the Angolan margin which represents one of the most favorable areas for the study of natural oil seepage. The aims of this study are to map natural oil seeps from a collection of satellite radar images, to estimate the lateral drifting of the oil from the emission point to the surface impact point, and to determine the seabed morphologies related to active oil seepages from the analysis of bathymetric and seismic data.
Use of Plasma-Shell Technology for Concurrent Control of Chemical and Microbial Contaminants
Authors: Kurtz Vicki
Published: May 2013

An emerging treatment system, based on using Plasma-Shells as a high surface area source of Ultraviolet (UV) light, holds promise for addressing some of the key microbial and chemical water quality issues faced by small water systems. Plasma-Shells are hollow dielectric gas encapsulating shells that can be energized to emit light over a broad range of wavelengths. When the shells are coated with titanium dioxide and energized, advanced oxidation reactions can occur in tandem with disinfection. By optimizing the wavelength characteristics, it is possible to achieve pathogen inactivation (~250 nm) and also promote photocatalytic reactions through excitation of titanium dioxide (~350 nm). From a water treatment perspective, the net effect of these reactions is disinfection and photocatalytic mineralization of waterborne contaminants. A key advantage of titanium dioxide coated Plasma-Shells over more traditional UV light sources is that all components are rugged, inert, and safe. The ceramic based shell material and the encapsulated gas (neon and/or xenon) are inert and, therefore, do not impact water quality. The system is highly water efficient and does not generate a waste stream or process residuals. In addition, there are no consumable chemicals that need to be stored on-site. The shells can be regenerated on-site through an off-line thermal system. The high surface area of the Plasma-Shells allows for a relatively small technology footprint, compared to more traditional disinfection or oxidation systems. The size of the Plasma-Shells and the process design configuration can be tailored to provide reaction conditions that are appropriate to address a broad spectrum of chemical and microbial waterborne contaminants.

Key elements of the technology include:Simple construction, rugged design, and scalable to meet site specific constraints.Modular process configuration that can be adapted to meet specific treatment requirements.Reliable source of UV light that is devoid of mercury or other potential environmental contaminants.High surface area to volume ratio that can provide efficient contact time for inactivating or mineralizing microbial and chemical waterborne contaminants.Efficient activation of titanium dioxide due to its direct contact with the UV light source.Use of a thin film of titanium dioxide obviates the need for post-treatment filtration and accomplishes the photocatalytic reaction in a single-step.
Migration of oil and its subsurface expressions in the deep-water Gulf of Mexico
Authors: Diaz Gustavo , Garcia-Pineda Oscar , Kahn Peter , Callejon Angel
Published: May 2013

The most robust evidence indicating that petroleum migrates in the Gulf of Mexico (GoM) is the presence of oil slicks at the surface of the sea coming from naturally sourced oil at the sea bottom.

The mechanisms for oil migration in the GoM involve the interplay of several variables (including faults, pressure, salt diapirism, etc.) These are not fully understood locally, let alone regionally, and are not well constrained to basin evolution. The use of numerical models helps to represent and visualize oil migration from the source to the traps and or seeps but it is limited by the lack of a complete geological picture. However, despite these limitations, numerical models are an important means of estimating the timing of oil migration.

Salt movement through time has a huge influence on the patterns of oil migration and re-migration. The underlying geometries of Allochthonous Salt can help focus oil to an up dip trap or in turn result in the breaching of a trap. Subsequent salt withdrawal may result in a weld which may or may not longer seal the hydrocarbons in place.

The characterization of successful plays in the GoM involves understanding seeps, oil fluxes, surface anomalies or hard crusts, along with plausible migration pathways of leakage and remigration of oil as related to salt tectonics. These elements are some of the building blocks to high-grade prospective areas for oil exploration.

Introduction

The first and most obvious observation is the presence of natural seepage occurring at the surface like sea-bottom pock marks and oil slicks (Fig. 1) The MacDonald Image Laboratory of Florida State University posted a video on the web (http://www.sarsea.org/natural_seapage/gallery.html) where it is possible to fully appreciate the most important characteristics of oil seepage: spatial variability of the point of origin, presence of carbonate hard crust, and domes and pock-marks.

Secondly, the identification of possible migration pathways relies on seismic data. By looking at deep seismic reflection data we can interpret mechanisms likely influencing petroleum movement from the source rock to the intermediate traps, and eventually into seeps. Interpreted faults and fractures seem to be the main conduits for oil migration.

The examples in this work show the dominant impact of salt movement on the migration. This salt was originally deposited over 160 mya. and has had a complex history of movement in resulting diapirs and salt canopies. Therefore, improving the combined knowledge of halokinesis, oil geochemistry and structural evolution of the basin it is possible to have a better picture of the migrating oil into traps, intermediate reservoirs and ultimately seeps.
Wind Testing of a Dual Derrick
Authors: Ross George , Beck Richard D , Jennings Tim , Jesudasen Sandeep , Martinez Jorge , Effenberger Mike , Botros Tammer
Published: May 2013

Wind loading on drilling rigs is covered by API Specification 4F 3rd Edition, Specification for Drilling and Well Servicing Structures. The specification gives procedures for determining design wind loads on new drilling rigs. These wind loads impose significant loads on offshore facilities and are critical for the design of derrick tie-downs.

The API 4F wind methodology was developed for wind loading on square derricks. However, drilling structures exist in shapes other than square. One example is a dual derrick.

BP has a dual derrick on the Thunder Horse platform. During a reassessment of the derrick, it became apparent that current methodologies may not properly determine the wind loads on a dual derrick. To determine if the existing 4F wind methodology was suitable for a dual derrick, BP undertook a program consisting of a literature review and wind tunnel testing. The testing was performed with major components added to the structure in stages to determine the contribution of various major components on the overall wind load.

This paper discusses the results of the wind testing on the dual derrick, provides comparisons of the resulting wind loads with the current API 4F methodology, methodology based on a literature search, a modified methodology viewed as minimizing risk of underestimating loads, and provides suggestions for future wind tunnel testing.

Introduction

On the BP Thunder Horse semi-submersible is a dual derrick. A dual derrick is a relatively new drilling structure used for deep water drilling operations. Efficiencies exist from allowing dual hook load operations that make this type of structure advantageous. Figure 1 presents a photograph of the Thunder Horse derrick from the V-door face (long front). The derrick has a width to depth ratio of 2 to 1 versus the 1 to 1 ratio of a more traditional square derrick.

The Thunder Horse Dual Derrick was designed using the methodology in the 2nd edition of API 4F. API has issued a new edition of API 4F, the third (3rd) edition. API 4F 3rd Edition had extensive revisions to the wind methodology. In addition, environmental design conditions for the Gulf of Mexico have also been revised. The new metocean design criteria contain updated/higher wind speeds for the location in the Gulf of Mexico where the Thunder Horse semi-submersible is located. BP wanted to investigate the dual derrick using the new API wind methodology and the new metocean criteria.

Evaluations were made with the wind methodologies from API 4F 3rd Edition, ASCE 7, and other wind documents for loading on the dual derrick long and short faces. Inconsistencies were found among the methods. As a result, BP was faced with a decision to use the most conservative wind load values or perform wind tunnel testing to better understand the loads on the structure. BP elected to perform wind tunnel testing.
Mass Spectrometric Analysis of Oxidized Eicosapentaenoic Acid Sodium Salt
Authors: Jordan Kelsey D. , Upmacis Rita K.
Published: May 2013

Eicosapentaenoic acid (EPA) is an omega-3 polyunsaturated fatty acid (PUFA) with 20 carbon atoms and 5 carbon-carbon double bonds. Mammalian cells cannot synthesize long chain PUFAs such as EPA de novo, and, thus, the most effective way to enrich cells in EPA is by dietary intake of fish oils. EPA supplementation causes an increase in its concentration in plasma lipids and in cell membrane phospholipids. Many beneficial effects of EPA supplementation have been noted, including (1) the potential to sensitize cancerous tumors towards chemotherapy, (2) the promotion of cardiovascular health, and (3) the alleviation of some mental disorders, but results from clinical trials have sometimes been disparate. In this study, we report the use of mass spectrometry to investigate the autoxidation of EPA, thereby demonstrating the formation of a variety of oxidized products. The oxidative stress of the patient may affect the response to EPA and may, in part, explain divergent results from clinical trials.
The topological K-theory of certain crystallographic groups
Authors: Davis James F. , Lück Wolfgang
Published: May 2013

Let

\Gamma

be a semidirect product of the form

\mathbb{Z}^n \rtimes_{\rho} \mathbb{Z}/p

where

p

is prime and the

\mathbb{Z}/p

-action

\rho

on

\mathbb{Z}^n

is free away from the origin. We will compute the topological K-theory of the real and complex group C*-algebra of

\Gamma

and show that

\Gamma

satisfies the unstable Gromov–Lawson–Rosenberg Conjecture. On the way we will analyze the (co-)homology and the topological K-theory of the classifying spaces

B Gamma

and

\underline{B} \Gamma

. The latter is the quotient of the induced

\mathbb{Z}/p

-action on the torus

T^n

.
Spectral triples for hyperbolic dynamical systems
Authors: Whittaker Michael F.
Published: May 2013

Spectral triples are defined for C*-algebras associated with hyperbolic dynamical systems known as Smale spaces. The spectral dimension of one of these spectral triples is shown to recover the topological entropy of the Smale space.
Lagrangian measurement of fluid and particle motion using a field‐deployable Volumetric Particle Imager (VoPI)
Authors: Tse Ian C. , Variano Evan A.
Published: May 2013

We describe the development of a field‐deployable Volumetric Particle Imager (VoPI) and the methods that enable it to measure three‐dimensional particle tracks in situ. The VoPI has the unique ability to obtain three‐component particle velocity records in a volume. The device has a slender, single‐camera design ideal for optically accessing study sites in the environment, including hard‐to‐reach places like the inside of coral reefs and marshes. Unlike other underwater measurement techniques, the VoPI implements a defocused imaging method that relies on ambient light in place of laser light for particle illumination. We describe the construction, calibration and validation of this device. We also demonstrate the VoPI&s abilities by measuring velocity statistics of passive tracer particles dispersed in a high‐Reynolds‐number turbulent flow. By measuring velocity variances and integral timescales from these Lagrangian velocity records, we can compute the turbulent diffusivity directly from the VoPI measurements.