bluuebunny/crossref_metadata_2025 huggingface dataset:
Developments in Computational Methods for Assessing Fatigue Life of Flexibles and Umbilicals
Authors: Dhaigude M. , Sharma P.
Published: June 2014

Flexible risers and dynamic umbilicals are being used increasingly in harsh environments which require reliable prediction of fatigue life. Predicting fatigue life of flexible risers and umbilicals are particularly challenging because of layered construction and helical components such as tensile armors and steel tubes. The basis for fatigue damage assessment of such elements is the long-term stress cycle distribution at critical locations on the helix elements caused by long-term environmental loading on the system. Establishment of the long-term stress cycle distribution requires global dynamic time domain analysis followed by cross-sectional analysis in a large number of irregular sea states.

An efficient fatigue analysis scheme is outlined in this paper. A detailed description is given of cross-sectional analysis techniques required for fatigue stress calculation in helix elements subjected to bending, tensile and pressure loading. Special emphasis is placed on assessment of friction stresses caused by the stick/slip behavior of helix elements in bending. These effects are considered to be of special significance for fatigue life calculations of deep water applications of flexible pipes and umbilicals due to increased contact pressure between the individual elements in the cross-section. A Joint Industry Project (JIP) with an objective of validating the stress calculation methodology by comparing with high quality bending tests has been initiated. Details of qualification testing for validating the methodology are also presented in the paper.
Interpreting the Past By Exploring the Abyss: Archaeological investigations of an early nineteenth-century shipwreck in the Gulf of Mexico
Authors: Horrell Christopher E. , Borgens Amy A.
Published: June 2014

Increasing deep-water oil & gas exploration, through its compliance with offshore regulatory oversight, has located significant archaeological sites in the Gulf of Mexico. These unsolved mysteries of the deep have much to tell about the unique history and culture of this region. Recently, an investigation of three early nineteenth-century shipwrecks located 170 miles off the Louisiana-Texas coast has yielded invaluable information. Following the discovery of three distinct yet unknown sonar targets during a Shell Oil seafloor hazard and archaeological survey conducted in 2011, video examination of one site, named Monterrey Wreck A, occurred in April 2012 with the National Oceanic and Atmospheric Administration (NOAA) Okeanos Explorer expedition. The tantalizing results of that expedition led to another more intensive investigation in July 2013 with a multi-team, multi-faceted mapping and artifact recovery effort. The privately funded 2013 archaeological investigation was affected through collaboration between varied federal and state partners, academic and nonprofit partners teaming archeologists, biologists, ROV specialists, and educators together in a public/private partnership to explore and learn more about this site. After detailed mapping of the wreck site, more than 60 artifacts were recovered, along with biological and sediment samples, intended to help identify and date the site and provide information about the environmental conditions occurring on a shipwreck at a depth of 4300 ft. During the 2013 investigation, the two nearby shipwrecks were also mapped and documented; confirming a hypothesis that the three shipwrecks are likely associated and perhaps lost during a single cataclysmic event such as a storm. Artifact conservation and analysis is ongoing, but preliminary research suggests that Monterrey Shipwrecks date to the early part of the nineteenth-century and are comprised of an armed vessel and possibly two consort cargo vessels or prizes. The 2013 expedition was broadcast live, via satellite, through the unique telepresence capabilities of the research vessel Ocean Explotation Trust (OET) Nautilus that enabled field archeologists and educators to describe the ongoing work and interact with the public. Continued public outreach includes report preparation and the creation of educational materials.
Assessing Uncertainty and Predictability of Regional Climate, with a Focus on Hurricanes
Authors: Holland G. J. , Done J. , Bruyère C.L.
Published: June 2014

The inherent uncertainty in - and predictability of - regional climate predictions over limited regions is assessed using a combination of simulations with the NCAR Nested Regional Climate Model (NRCM) and statistics. Our focus is on climate and weather extremes that have high impact on society and how these may be changing with both climate variability and change. This presentation will focus on hurricanes over the Gulf of Mexico.

An ensemble of state-of-the-art NRCM simulations is used to assess the uncertainty arising from choice of: various physical processes, initial conditions, domain sizes, boundary conditions and model breeding techniques. The objectives are to:increase our understanding of the ability of regional climate models to capture regional climate information - both at the individual and collective ensemble member levels;investigate the role of different combinations of processes in reproducing regional climate; andestimate the associated uncertainty and inherent predictability.

The study is geared towards an improved ability to select optimal combinations of model configurations to maximize the predictive signal for local climate extremes. Initial results from this assessment will be presented. In particular, we include examples specific to potential future changes in hurricane impacts on Gulf of Mexico offshore facilities.
Squall Characterization in the Gulf of Mexico
Authors: Jeans G. , Cooper C. , Yetsko C. , Bryan G.
Published: June 2014

This paper describes a new analysis of meteorological data that improves the understanding and characterization of winds generated by squallsin the Gulf of Mexico. The analysis begins by looking at a particularly strong squall event observed in April 2013 that created gusts that likely approached 40 m/s. Not only was the April squall extremely strong but the wind direction changed rapidly which is often very challenging to dynamically positioned vessels. Indeed one deepwater drilling rig had to make an emergency disconnect during the event. To put the April event into proper historical perspective, the paper produces preliminary estimates of squall gust probability levels based on public domain datasets. This analysis suggests that the April squall was probably close to the 100-yr event and was thus, quite rare. Perhaps more importantly, the analysis shows the 10-yr gusts from squalls exceeds the API 2MET 10-yr estimates for winter storm. This is a significant finding since the 10-yr winter storm is recommended for operating criteria in the Gulf by API recommended practices covering multiple types of offshore facilities. That said, the estimates in this paper are preliminary and further work is needed to remove uncertainty in the n-yr speeds and to quantify rapid wind direction changes before any changes to present operating criteria should be contemplated.
A Post-Installed Subsea Monitoring System for Structural and Flow Assurance Evaluation
Authors: Brower D.V. , Brower A.D. , Hedengren J.D. , Shishavan R. Asgharzadeh
Published: June 2014

This paper describes major advancements for deploying sensing systems on existing subsea structures as part of the Clear Gulf study. In the past, a major shortcoming of post-installed monitoring systems has been poor coupling between the sensor and structure; this study provided methods to overcome this problem. Both subsea field testing and laboratory testing were performed to verify these advancements. The Clear Gulf study is a collaboration between the offshore energy industry and NASA with the goals of risk mitigation, safety, efficiency and environmental concerns in the offshore energy industry. The study is ongoing and has investigated new methods to improve deepwater monitoring and addresses installation of advanced sensors on already-deployed risers, flowlines, trees, and other subsea assets. These highly sensitive monitoring systems will provide operators a cost-effective method for detecting and responding to potential failures, flow assurance issues, and catastrophic events.

A significant achievement was recently made in bonding methods in subsea environments. Prior to installation on Tension Leg Platforms (TLPs), subscale test articles were fabricated and tested. There was a slight decrease in bonding strength, however, the methods demonstrated adequate adhesion for structural coupling integrity on subsea components. Aging tests were conducted to ensure long-term service life potential.

Full-scale implementation was accomplished on two TLPs in West Africa. Two challenges in calibration of the post installed sensors are determining the baseline or zero state of stress and sensitivity of the fiber Bragg gratings on the clamp to actual load changes on the structure. The effectiveness of the monitoring system was enhanced by calibration methods employing fundamental predictive methods to establish both baseline and sensitivity values. The transition layer between surface and deep water levels (thermocline) required temperature compensation of the strain sensors. Vastly changing temperature profiles were measured and analyzed at this moving boundary. A method to isolate temperature effects from structural data was developed and integrated into the software algorithm. A multiplexing method was incorporated with minimum cabling and connectors to make the system redundant and fault-tolerant to inadvertent cable damage. With this unique design, severing the cable in one location leads to no loss of data.
Performance Testing of an In-Line Electrocoalescer Device with Medium and Heavy Crudes
Authors: Grave E.J. , Olson M.D. , Menchaca A.E. , Westra R.W. , Akdim M.R.
Published: June 2014

ExxonMobil Upstream Research Company (EMURC) recently completed a subsea technology development and qualification program which included performance testing of an in-line electrocoalescer device supplied by FMC Technologies (FMC). This paper will summarize the results from these performance tests.

Although heavy oil has been processed on-shore successfully for many decades, processing heavy oil in deepwater, subsea, or Arctic fields is extremely challenging. One key challenge is oil-water separation, in which physical separation is constrained by the high viscosity of the crude and the narrow density difference between oil and water. Installing conventional electrostatic coalescers or dehydrators is often not economical or impractical at remote locations. As part of ExxonMobil's subsea program, several different separation technologies have been investigated and tested that could enable development of these fields. One example of such a technology is FMC's InLine ElectroCoalescer (IEC).

FMC has developed an innovative, compact electrostatic technology that enhances the coalescence of water droplets dispersed in emulsified oils. This technology has the potential to considerably improve the performance of the downstream oil-water separator. By applying an electrical field to an oil-water mixture, the dispersed water droplets become polarized and reorient themselves in the electrical field. As these water droplets approach one another, attractive forces between the individual water droplets lead to coalescence. Larger water droplets are formed, that can be separated faster and more easily in the downstream separation equipment. The IEC can be used to increase the throughput, performance, and reliability of existing oil processing systems while reducing the energy consumption and/or use of chemical demulsifiers. In new processing systems, either subsea or topside, deployment of the IEC has the potential to significantly reduce the size and weight of the downstream separation equipment, thereby lowering the overall capital expenditure.

The results presented in this paper are from performance tests that have been carried out on the IEC at FMC's testing facilities in the Netherlands, under EMURC's supervision. Extensive testing was executed with both medium and heavy crude oils. The operating temperatures were varied in a range representative for subsea processing applications, where heating of the process fluids is difficult. Thus, the performance of the IEC was evaluated over a range of oil viscosities. Water-in-oil concentration, flow velocity, upstream shear, and electric field strength were also varied to investigate their effects on the IEC performance. The results demonstrate that the IEC is able to deliver high pre-conditioning performance to medium and heavy crude oil emulsions, given the appropriate process conditions and electrical settings are used.
Guest Molecule Exchange Kinetics for the 2012 Ignik Sikumi Gas Hydrate Field Trial
Authors: White Mark , Suk Lee Won
Published: June 2014

A commercially viable technology for producing methane from natural gas hydrate reservoirs remains elusive. Short-term depressurization field tests have demonstrated the potential for producing natural gas via dissociation of the clathrate structure, but the long-term performance of the depressurization technology ultimately requires a heat source to sustain the dissociation. A decade of laboratory experiments and theoretical studies have demonstrated the exchange of pure CO2 and N2-CO2 mixtures with CH4 in sI gas hydrates, yielding critical information about molecular mechanisms, recoveries, and exchange kinetics. Findings indicated the potential for producing natural gas with little to no production of water and rapid exchange kinetics, generating sufficient interest in the guest-molecule exchange technology for a field test. In 2012 the U.S. DOE/NETL, ConocoPhillips Company, and Japan Oil, Gas and Metals National Corporation jointly sponsored the first field trial of injecting a mixture of N2-CO2 into a CH4-hydrate bearing formation beneath the permafrost on the Alaska North Slope. Known as the Ignik Sikumi #1 Gas Hydrate Field Trial, this experiment involved three stages:the injection of a N2-CO2 mixture into a targeted hydrate-bearing layer,a 4-day pressurized soaking period, anda sustained depressurization and fluid production period. Data collected during the three stages of the field trial were made available after an extensive quality check. These data included continuous temperature and pressure logs, injected and recovered fluid compositions and volumes. The Ignik Sikumi #1 data set is extensive, but contains no direct evidence of the guest-molecule exchange process. This investigation is directed at using numerical simulation to provide an interpretation of the collected data. A numerical simulator, STOMP-HYDT-KE, was recently completed that solves conservation equations for energy, water, mobile fluid guest molecules, and hydrate guest molecules, for up to three gas hydrate guest molecules: CH4, CO2, and N2. The independent tracking of mobile fluid and hydrate guest molecules allows for the kinetic exchange of guest molecules between the mobile fluids and hydrate. The particular interest of this numerical investigation is to determine whether kinetic exchange parameters, determined from laboratory-scale experiments, are directly applicable to interpreting the Ignik Sikumi #1 data.
Case Study of Geotechnical Site Investigation using a Seafloor Drilling Unit, Large-diameter Cores, and Coring-vessel-deployed Cone Penetration Tests in the Gulf of Mexico
Authors: Caruthers C. , Hartsfield R. , Young A.G. , Spikula D. , Dobias J. , Fitzpatrick M. , Remmes B.
Published: June 2014

This paper compares results of a deepwater geotechnical investigation using a seafloor drilling system, large-diameter core samples, and cone penetration tests performed from a coring vessel with results of a geotechnical investigation performed from a conventional drillship. The paper reports the first use of a seafloor drilling unit in the Gulf of Mexico to conduct a geotechnical site investigation for the mooring design of a floating platform.

Common practice in the Gulf of Mexico for geotechnical investigations of anchor spreads for moored production facilities has been to perform seafloor cone penetration tests and to drill and sample one or more soil borings. "Soil borings" are prescribed but not defined by 30 CFR 250.19 API RP 2SK1 recognizes currently available site investigation tools, such as large-diameter core samples, that could be used in lieu of rotary soil borings; however, some certified verification authorities/agents (CVAs) have been reluctant to accept the use of API-accepted methods of site investigations in the Gulf of Mexico. Seafloor drilling units have been used successfully in various parts of the world, and cone penetration tests from a coring vessel have been performed and studied at numerous sites, both in the Gulf of Mexico and worldwide. This paper demonstrates that a seafloor drilling unit, large-diameter cores, and coring-vessel-deployed cone penetration tests integrated with AUV subbottom profile data can be used in the Gulf of Mexico without reliance on samples obtained from a drillship.

Cone penetration resistance is compared using different cone systems and deployment methods at nearby locations. Results are essentially identical. Representative soil sample data are compared, and geotechnical laboratory test results are very similar. The paper confirms that when ASTM standards for cone testing and thin-walled-tube sampling are used, consistent results can be obtained from site investigations performed from seafloor drilling units and coring vessels or purpose-built geotechnical drillships. Integrated site investigation programs using technologies such as seafloor drilling units, large diameter coring, and cone penetration testing from a coring vessel should be acceptable for site investigations without special regulatory approvals beyond those that would apply to a site investigation program performed from a purpose-built geotechnical drillship.
AUV-Based 3D Laser Inspection for Structural Integrity Management in Deepwater Fields
Authors: Reeves T. , McLeod D. , Embry C. , Nickerson B.
Published: June 2014

Lockheed Martin has developed the capability to conduct AUV-based structural survey and post-hurricane platform inspection using 3D mapping and change detection with a 3D sonar. Successful validation trials for this technology were conducted with the Marlin® AUV during the summer of 2011 and the first commercial operations were conducted in the summer of 2012.

Lockheed Martin Corporation, in partnership with underwater laser developer 3D at Depth LLC, and supported by funding from the Research Partnership to Secure Energy for America (RPSEA), is now extending its revolutionary 3D modeling and change detection to employ a 3D laser sensor, thereby improving model resolution and accuracy by an order of magnitude, from centimeter scale to millimeter scale. AUVs outfitted with 3D Laser imaging systems will provide new, high accuracy tools for subsea integrity management that are currently used extensively in terrestrial applications, including High Definition Scanning (HDS) for close-in inspection of problem areas, and underwater LIDAR (LIght Detection And Ranging) for 3D mapping and inspection of flowlines, risers, and other subsea infrastructure.

The scope of this project is to develop and demonstrate the technology required to conduct AUV-based 3D-laser imaging utilizing 3D mapping and change detection. Objectives include demonstration of close-in, high resolution underwater structural inspection, generation of high resolution 3D models of subsea structures, and performance of change detection of flaws or damage against a priori structural models.

This paper will detail the results achieved to-date and will highlight the 3D Laser performance improvements over current platform inspection methods, including significant improvements in operating efficiencies and the development of accurate 3D models for use in structural integrity management.
Integrating hydrodynamic and nautical studies for offshore LNG operations
Authors: Voogt Arjan , Wilde Jaap de , Dekker Johan
Published: June 2014

For offshore LNG production, the ability to safely offload LNG to shuttle carriers is an important driver in the design. Hydrodynamic studies and nautical studies can be used to select an offloading concept, optimize the operational procedure and evaluate the terminal availability. These studies involve mariners and mathematics. Full mission bridge simulators are traditionally used to train for the operation and to evaluate its feasibility. By incorporating state-of-the-art hydrodynamic models, the full mission bridge simulator can also be used for concept engineering. This allows a bridge between design and operation. It provides feedback from the operation into the design and improves operational guidance. This paper shows examples of this approach, while evaluating both tandem and side-by-side offloading.

With hydrodynamic studies the relative motions and mooring loads between the permanently moored vessel and the transport vessel are estimated. This paper concludes that 97% weather uptime can be achieved in waves with up to 3 meters significant height for side-by-side while the same uptime can be achieved in waves up to 5 meters for dynamic positioned tandem offloading. Tandem offloading is often perceived as a safer option than side-by-side offloading, due to the larger distance between the vessels. Although the tandem configuration seems more promising for offshore offloading, it requires new technology for LNG transfer, which is why it has not yet been applied. Integrating hydrodynamic and nautical studies can help to evaluate cryogenic hose handling and tug operations during the final phase of the approach and departure of the LNG carrier.
Practical Application of CFD Modeling of Air Gap and Wave Loads in Offshore Structure Design
Authors: Wu Guangyu , Danmeier Don
Published: June 2014

This paper presents a recent practical deployment of Computational Fluid Dynamics (CFD) modeling of wave-structure interaction to support the design of an offshore gravity-based structure. Advanced CFD modeling was employed, as a supplement to conventional analysis tool and model testing, to improve the design assurance in estimating the air gap and wave loads on the offshore structure. Through the design process, a series of CFD simulations were performed:before the model test, CFD simulations were used to identify the potential for wave breaking and guide the wave generation in the wave basin, and the predicted air gap and local pressure distributions informed the arrangement and sizing of instruments in the model test;immediately after the model test, extreme wave conditions from the model test were simulated in CFD to corroborate time histories of air gap, wave run-up, global loads, and hydrodynamic pressure on structure surfaces; andpost model test, the validated CFD simulations were then employed to provide additional information unavailable from the model test (e.g. detailed flow field and pressure distribution on the structure) to guide structure design and analysis. Our overall practice demonstrated that CFD modeling of wave-structure interaction can be effectively integrated into today's offshore engineering design process and improve design assurance of the facility.
BP Angola PSVM Project: Production Flowline Lateral Buckling Design
Authors: Cooper P.A. , Crawford M.J. , Bell M.
Published: June 2014

The BP Angola Programme focuses on the development of a number of deepwater oil production projects within the Angolan Offshore Block 31 and 18. PSVM is the first field under development within Angola Offshore Block 31 and uses a centrally located FPSO with subsea ‘offline’ manifolds and clustered wells located in water depths up to a maximum design of 2100m. The extensive production flowline system features three "hybrid loops", compromised of highly insulated pipe-in-pipe production flowlines, with the remote end linked to the host FPSO by a single wall service flowline for dead oil displacement and inspection pigging.

During the design, a number of technical challenges were identified, requiring collaborative approaches and complex numerical analysis to develop a robust final solution. These challenges included balancing the effects of sour produced fluids and slug flow on fatigue strength, with the thermo-mechanical design including buckling and walking mitigation. The combination of a heavy pipe-in-pipe cross section and very soft seabed soils further complicated the design. The buckling design solutions developed were compatible with installation in 2km water depth, used proven and qualified methods and materials and ensured integrity for the 25 year design life.

This paper outlines the approach to thermal expansion management through engineered lateral buckles. The selection of buoyancy sections in preference to sleeper arrangements, which have been popular in the past, are explained.

The main features of the final design are described, including procurement, construction and installation considerations. Observed buckling response from commissioning and early production is compared with design predictions, and key lessons learnt are shared.

The paper seeks to demonstrate the merits of buoyancy modules in preference to sleepers as buckle mitigation devices for deepwater flowlines. Key design considerations are identified, and a rational design process consistent with SAFEBUCK and DNV guidance is outlined.
Numerical Simulation of Floating Offshore Wind Turbines Including Aero-Elasticity and Active Blade Pitch Control
Authors: Sweetman Bert , Wilder Blake
Published: June 2014

A new numerical methodology is presented for simulation of dynamic behavior of floating offshore wind turbines. Wind forces are computed in the time domain through application of blade element momentum theory using the instantaneous wind velocities, blade pitch angles, and resulting rotor speed. Equations of motion are developed and solved in Euler-space, such that no small-angle assumptions are required in the solution; vessel motions are included in wind and wave force calculations. Aero-elastic effects are quantified using the industry-standard subroutine AeroDyn, with blade pitch-angles computed by the "DISCON" subroutine, both open-source and publicly available from the National Renewable Energy Lab (NREL). Effectiveness is demonstrated through a series of examples, first a case for small-angle motion is compared with results from an industry standard simulation tool for the spar-based NREL OC3-Hywind with constant wind speed and no waves; next, the same environmental conditions are applied to a smaller spar-based floater for which standard simulation tools would not be applicable. Finally, a case is presented including irregular winds and waves.
API 17TR12 – Consideration of External Pressure in the Design of Deepwater Subsea Equipment
Authors: Williams Mike , Pham Man
Published: June 2014

This paper presents an overview of API 17 Technical Report TR12: Consideration of External Pressure in the Design and Pressure Rating of Subsea Equipment, a technical report prepared by a work group under the auspices of the API Subcommittee 17 (API SC17). This subject is of significant interest for current deepwater subsea projects where well shut-in pressures may only be slightly higher than 15K API Rated Working Pressure (RWP), and progressing to 20K API RWP equipment results in significant cost increases and/or delivery delays. At first glance, it seems logical that the high external seawater pressure in deep water (3000 – 4500 psi) could offset a significant portion of the internal pressure, keeping the differential pressure acting on the equipment to 15K equivalent, or less. This would allow for a higher well shut-in pressure than the equipment API RWP with consideration to the external hydrostatic pressure. This approach has been taken with 10K equipment on several medium water depth projects in the past (with special qualification testing). However, recent regulatory rulings and technical studies have called this practice into question. There are several technical issues discussed in this paper, some subtle, that must be evaluated and resolved before attempting to use equipment above its API RWP based on the presence of external hydrostatic pressure (from ambient seawater pressure or from the fluid column in risers or flowlines). API 17TR12 contains detailed guidelines on these issues, and proposes methods for evaluation and qualification that should be used when considering the effects of hydrostatic external pressure on API RWP.
Canada's Cabled Ocean Observatories
Authors: Moran Kate , Pirenne Benoit , McLean Scott , Round Adrian , Juniper Kim , Macdonald Nikki , Madden Peter
Published: June 2014

Ocean Networks Canada (ONC) is the not-for-profit agency responsible for the management of VENUS, the coastal observatory, and NEPTUNE, the regional observatory, on behalf of the University of Victoria, lead institution for a pan-Canadian consortium of universities, industries and government agencies. ONC's vision is to be a world leading organization supporting ocean discovery and technological innovation.

ONC's mission is to enable transformative ocean research and technology development through an innovative cabled infrastructure that supplies continuous power and Internet connectivity to a broad suite of novel subsea instrumentation in coastal and deep-ocean environments.
Operating Performance Forecasting and Evaluation of an FPSO with Degrading Mooring System Components
Authors: Carra C. , Wales S. , Gumley J. , Jobson B. , McDonnell S. , Mir U.
Published: June 2014

Integrity management of mooring systems on floating structures has been gaining interest over the last few years, as a result of increasing interest in life extension of existing assets and the reported increase in the number of mooring system failures. During the second half of 2012, OMV New Zealand Ltd commenced planning for a detailed inspection program of all underwater assets in the Maari Field, including the mooring system for the FPSO Raroa. When conducting the campaign in early 2013, a series of anomalies were found, including birdcages in wire sections of adjacent mooring legs. Through a regime of coordinated metocean forecasting, metocean monitoring, FPSO position monitoring, numerical modelling and ongoing inspection, OMV New Zealand was able to effectively manage an FPSO found to have multiple adjacent degraded mooring lines through a winter season until repairs could be completed. The development of a concurrent numerical model of the actual mooring system proved to be indispensable in achieving this objective and in facilitating the day-to-day operation of the facility over this period. Being able to verify numerical predictions against actual vessel motion response data in combination with detailed site metocean data significantly enhanced the value of the numerical model. The numerical model was employed across a wide range of activities from forecasting performance, evaluation of hypothetical multi line failure scenarios, interpretation of measured performance, determination of sea state limits and inspection triggers, through to the remediation engineering of the system. Of particular importance for the Maari situation was the early detection of potential line failure on the degraded leeward mooring legs, which was heavily reliant on comparisons of numerical predictions against observed system behavior.
Signatures of Mid-Water Jets in the Gulf of Mexico BOEM NTL Dataset
Authors: Magnell Bruce A. , Ivanov Leonid I.
Published: June 2014

We discuss the results of a process-oriented analysis of current profile measurements collected from 2005 through 2010 in the Gulf of Mexico by oil industry operators, who are required to measure ocean current profiles and transmit these data in near-real-time. The individual data ensembles are sent to NDBC where they are processed, quality checked, archived and made available to the public through the NDBC website. WHG performed a thorough inspection of the data, including a review of the temporal and spatial continuity of the data, cross-check between neighboring stations and between current data and satellite altimetry charts, and verification of the metadata using independent sources of [1].

The cleaned and quality-controlled data were analyzed to identify and classify the observed cases of stronger currents. The analysis identified 140 cases of current events characterized by a subsurface ‘jet’ peaking at 30–50 cm/s that does not have a surface expression.. In most of the mid-water current events identified in the 2005–2010 NTL data, the current speed peak is located somewhere between 300m and 800m, most frequently around 500m, much deeper than similar patterns identified in earlier studies. Some of the events identified in our study lasted for less than one day, but many events were of a much longer duration. Most of these events were observed southeast of the Mississippi delta and had horizontal scales over 15 miles and lingered in the area for an extended period of time. Some of the identified events were caused by strong inertial oscillations with multiple speed peaks confined to a relatively narrow layer centered around 500m. Mid-water jets have been identified in previous work [2] but this new analysis provides far more cases and suggests that the jets have an upper limit of about 50 cm/s. Such magnitudes are unlikely to govern extreme loads on offshore risers or tendons but they could be a factor in fatigue.
Qualification of UOE Linepipes with Enhanced Collapse Resistance
Authors: Arroyo Moreira F. , Silva R.C. , Mantovano L.O. , Solano R.F. , Azevedo F.B. , Alves H.
Published: June 2014

Large diameter UOE pipes are being increasingly used for the construction of offshore pipelines and in the last few year, since oil discoveries are moving towards ultra-deepwater areas, such as Pre-Salt in Brazil, collapse resistance is a key factor in the design of the pipelines the demand for pipes with high thickness near the limits for fabrication and installation capacity. It is known that the cold forming, and the final expansion in the UOE line pipe manufacturing process, reduces the elastic limit of the steel in subsequent compression. Due to this, the DNV collapse formula includes a fabrication factor that de-rates by a 15% the yield strength of UOE Pipes. However, DNV also recognizes the effect of thermal treatments and the code allows for improvement of the fabrication factor when heat treatment or external cold sizing (compression) is applied, if documented. In previous work [1] it was presented the qualification of UOE pipes with enhanced collapse capacity focusing the use of a fabrication factor (alpha-fab) equal to 1. A technology qualification process according to international standard has been performed. The main aspects of the qualification process were presented and included significant material, full scale testing and final analysis. In this paper, we compare those results with the ones of the new qualification tests analyzing the more important variables affecting the collapse resistance such as ovality, compressive material strength, thermal treatment control, etc. This new qualification obtained even better results than the previous one, which will allow the use of a fabrication factor equal to 1 directly in deepwater and ultra-deepwater offshore pipeline projects with a possible reduction in material and offshore installation costs and also potentially enhancing the feasibility of many challenging offshore projects.
CFD-FE Simulation of Wave Slamming on an Offshore Platform in Extreme Sea States
Authors: Kim Jang , Jang Hyunchul , Izarra Rafael , Martin David , Dalane Oddgeir
Published: June 2014

Fluid flow and structural deformation of a floating platform during extreme wave slamming events are simulated by Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) in coupled ways, in both model and full scale. The objective of the simulations is to verify correlation between slamming impact pressure on scaled platform model in the wave basin set up and full-scale platform in the real sea when the rigidity of the hull surface is considered. The slamming load and structural response simulated by CFD-FE analysis is first validated against analytic solutions and model tests for the following two cases:Wave slamming on rigid wall by breaking wave and water hammerDrop test of rigid and elastic structure on calm water

The validated CFD-FE simulation set up is then applied to simulate wave slamming on three different realizations of a Spar hull structure:Rigid hull at model scaleRigid hull at full scalePressure panel at model scale

In the CFD-FE modeling of the wave slamming at full- and model scale, compressibility of water/air and elasticity of the hull are properly modeled to simulate the difference between the hydroelastic effects at model- and full-scale set up. It has been found that the hydroelastic effect is minimal on full-scale Spar structure but can be significant on pressure panels at model scale. Further CFD investigations on other physical parameters that might affect the difference between wave slaming load at full- and model scale, such as surface tension, air entrapment and air-water mixture properties are made.
Fluid-Structure Interaction and Applications to Screening Pipeline Span VIV and Subsea Piping FIV
Authors: Pontaza J.P.
Published: June 2014

Flow-induced vibrations (FIV) of subsea piping due to external flow (e.g., vortex-induced vibrations of pipeline spans) or internal flow (e.g., high velocity multiphase flow in subsea piping) may pose structural integrity concerns due to cyclic stressing at critical welds and, over time, a threat of fatigue failure. Assets in the design stage or in the operating stage which fail a screening based on published guidelines, may undergo a comprehensive screening based on numerical simulation. This paper gives an overview of such a screening methodology, based on computational fluid dynamics (CFD), structural finite element analysis (FEA), and associated fluid-structure interaction (FSI).

In the context of pipeline span VIV, seabed proximity effects and flow blockage effects may have a significant effect on the pipeline span response. High-level screenings based on DNV-RP-F105 may not account for these effects appropriately and result in overly conservative fatigue life estimates. We present a couple of application cases where the comprehensive screening makes evident these conservatisms.

In the context of FIV (due to internal flow) a high-level screening approach exists as part of the Energy Institute (EI) Guidelines on the Avoidance of Vibration Induced Fatigue Failure (AVIFF). However, the EI AVIFF guideline does not provide a framework for the direct estimation of vibration levels, stress levels, or fatigue life. The comprehensive screening methodology addresses this gap and is illustrated with an application case.

Vibration measurements and piping remediation are much more costly subsea than they are on topsides. Hence, advanced simulation techniques are valuable tools in determining the integrity status as well as the safe operating limits of subsea piping.
Cutting Edge Seismic Technology Boosts Mars B Project by Delivering Exploration, Maturation and Development of Two Subsea Fields Tied Back to New Olympus TLP at a Top Quartile Pace
Authors: Sloan Robert F. , King Kevin M.
Published: June 2014

Deimos, discovered in 2003, consists of numerous high quality oil reservoirs which increased the depth and subsalt extension of the Mars Field. It was followed up one year later by the up-dip dry-hole exploration well, Boreas. The subsurface results from Boreas were sufficiently disappointing to discourage further exploration in the subsalt portion of the Mars Basin. Both Deimos and Boreas were drilled using our best seismic of the time, PrestackDepth Migrated narrow azimuth (NAZ) streamer data. However this data was insufficient in imaging the structural and stratigraphic complexities apparent in this subsalt environment.

Following the success of the Deimos Phase 1 Development, Shell acquired its first Ocean Bottom Seismic – Full Azimuth (OBS) survey in 2007 to plan Phase 2 of Development. The improvement in the seismic image over Deimos and the surrounding subsalt area was dramatic. The OBS along with an anisotropic corrected velocity model seismic data set resulted in a step change in our geologic and stratigraphic understanding of the subsalt portion of the Mars Basin. Two exploration opportunities, West Boreas and South Deimos were quickly identified. The new data also indicated that the Boreas dry-hole missed West Boreas by < 200 ft, and drilled through a previously un-imaged fault which cut out most of a high quality reservoir sand.

The OBS seismic image facilitated a high quality interpretation of the subsalt portion of the Mars Basin that not only enabled the rapid maturation of the exploration opportunities, but also allowed for the sanctioning of the Mars B subsea development with only one penetration into each of the newly discovered fields. The seismic-to-well ties had an excellent match and instilled high confidence in our seismic interpretation and geologic modeling which enabled Shell to progress the Mars B subsea development at a rapid pace.

One of the largest risks to any subsalt development is the uncertainty of the target reservoir's quality, extent and structure. To date, two of the six proposed subsea development wells have been drilled, and the well results have confirmed our confidence in the quality of the OBS seismic. These subsea wells will be tied back to Mars B's newly installed Olympus TLP and deliver its first oil in 2014.
Mars B Development - Well Challenges & Solutions - An Evolution of Traditional Well, Rig and Facility Design
Authors: van den Haak Arno L.M. , Cameron Wylie J. , Grant Lisa S. , Japar Nor Janiah H. , Reagins Deandre R.
Published: June 2014

The Mars-B project is Shell's sixth GOM TLP development and demonstrates Shell's commitment to GOM. The Mars-B project is aiming to unlock resources over the next 50 years through the deployment of a new 24 slot TLP structure (Olympus TLP) and additional subsea infrastructure for the West Boreas/South Deimos fields. The Olympus DVA rig is a novel platform drilling rig designed specifically to meet the execution requirements of complex Olympus DVA well designs. The well design and associated equipment must accommodate the 50 year design life, the longest design life of a TLP in Shell's history.

This is the first development to incorporate post-Katrina environmental design loads and new regulatory design requirements. Project challenges include numerous technical challenges pertaining to well designs for 24 DVA wells targeting over 50 horizons spanning 10, 500 ft TVD to approximately 25, 000 ft TVD encompassing both highly depleted brown field and deeper virgin pressure formations.

The Olympus DVA well trajectories range from near vertical to high angle extended reach both through sediments and through salt penetrations. Rig and surface facilities must be designed to address multiple challenges present to ensure well and facility integrity, reservoir isolation and desired well construction objectives are met. This requires successful development and deployment of novel technologies and world class systems. The design requirements have resulted in an evolution of traditional well designs which in turn drives novel rig and surface facilities requirements.

A high level overview of the design challenges and the resulting surface equipment requirements will be discussed. This includes rig equipment requirements to meet the specified execution directives, the development of an innovative drilling riser concept, added systems optimization to increase safety and overall execution efficiency.
New Hydrate Anti-agglomerant Formulation for Offshore Flow Assurance and Oil Capture
Authors: Sun Minwei , Firoozabadi Abbas
Published: June 2014

Gas hydrate formation often blocks flowlines in oil and gas production due to low temperature and high pressure, and may result in serious safety and environmental problems. Risk management of gas hydrate is a major challenge in offshore hydrocarbon production. Anti-agglomerantion (AA) is an attractive option because of effectiveness at low dosage and high subcooling. Hydrate particles are kept small and allow flow in slurry form, therefore avoiding plugging in flowlines. Until recently various authors have believed that anti-agglomeration is based on the formation of water-in-oil emulsion. We have demonstrated that the process can occur without emulsion or through oil-in-water emulsion. We have shown anti-agglomeration in methane and in one natural gas system. In this work, we demonstrate the effectiveness in two natural gases and in a crude oil system. In the crude oil, the effectiveness is shown in both water and in brine. These demonstrations pave the way for vast potential applications in both offshore flowlines and in oil capture from the seabed.
Early Production Systems – When Do They Make Good Sense for Your Project?
Authors: Coopersmith Ellen M. , Burkholder Kent , Mendoza Luis
Published: June 2014

Many teams believe an Early Production Systems(EPS) will be valuable for their offshore projects, but struggle when asked to make the business case. Typically, if there is value in an EPS it is derived either from early resource sales and or providing information on key dynamic uncertainties in order to decide whether and or how to optimize development. The latter often being the driver of value.

As the industry moves to deeper and deeper waters, getting quality information on dynamic uncertainties gets more expensive and for some, cost prohibitive. As a result, companies either need to be willing to sanction expensive developments with sizable risk (potentially bearing a higher risk tolerance) or find ways to make extended tests or Early Production Systems compelling financially in addition to technically.

The key dynamic uncertainties teams often want to reduce before sanctioning development are compartmentalization, natural or enhanced drive mechanism and or initial production rate. Each is linked to different decisions which can be optimized given uncertainty is reduced. Compartmentalization directly affects the number of development wells, drive mechanism affects the need for injection, associated well count and facilities and initial rate directly affects facility size.

Ultimately, the key to deriving value from an EPS resides in its design, which includes the type of EPS vessel, the associated fiscal terms and the quality of the information gathered from the early production system prior to finalizing development (Mastrangelo, et al. 2003, Valenchon, et al 2000). This includes the tests and data to be collected, as well as the duration of the production period prior to making the important development decisions.

This paper discusses the design aspects which drive value of an EPS and introduces a stepwise approach for teams to follow to frame and evaluate dynamic tests and EPS design options using a generic deepwater case example. Alternatives ranging from a drill stem test (DST) to an EPS to a tie-back are compared and sensitized to understand under which conditions each option might be worthwhile, ultimately providing information for an informed decision.