bluuebunny/crossref_metadata_2025_split huggingface dataset:
Qualification of Flexible Dynamic Risers for Supercritical CO2
Authors: Rubin Adam , Wang Christian 
Published: April 2012

Abstract
In the oil and gas industry there is a growing demand for riser solutionsdedicated to high partial pressures of CO2. Part of this demand is driven bydeep water high pressure reservoirs with high CO2 content. In addition there isa growing interest in reinjection of CO2. The reinjection can be driven by adesire to reduce CO2 emission as in Carbon Capture and Storage (CCS) projects, but also as a way of Enhanced Oil Recovery (EOR). In all cases it is likelythat CO2 will be present at high pressures and in its supercriticalphase.
NKT Flexibles is about to complete a three-year documentation and qualificationprogram with the aim of qualifying a broad range of flexible pipe solutions foruse with supercritical CO2 (SCCO2). An important part of the program has beenmaterial qualification. For polymeric materials, the main challenge is the highsolubility in some polymers of supercritical CO2. This leads to potential highswelling and a risk of mechanical damage (blistering) in explosivedecompression situations. Furthermore, supercritical CO2 has a strongextraction power which may result in rapid loss of plasticizer in plasticizedpolymers.
The qualification program included a broad variety of tests qualifying againstpotential failure mechanisms. The testing program is executed on polymers incontact with the bore stream. Results show that cross-linked poly-ethylene(XLPE) inner liner has superior resistance to SCCO2 on all tested parameterscompared to other available liner materials.
For steel materials, the main potential risk when exposed to supercritical CO2is corrosion. High CO2 content together with water forms a corrosiveenvironment which could have some impact on the metals used. For flexible pipeapplication, this is primarily relevant for the carcass material and endfitting which is in direct contact with the bore stream. Selection ofappropriate metallic materials will be based on the actual specification of thebore stream.
This paper will present the full scope and results of the qualification workcompleted for qualification of flexible dynamic risers for SCCO2.

Introduction
For the last 35 years, unbonded flexible pipes have been a key component inoffshore oil and gas production. They represent an alternative solution torigid steel pipes where they have the advantages of faster installation timesand better adapting potential for changes in field layout. These advantagesoften make unbonded flexible pipes a more economical solution than rigid steelpipes.
Mooring Lines - Integrity Management
Authors: Ukani Sandip , Maurel Walter , Daran Renaud 
Published: April 2012

Abstract
The Floating Product Systems (FPS) fleet has increased steadily over the last 2decades and is expected to continue to grow with developments in the world'sdeepwater basins. One of the issues with floating installation is that they aremoored to the seabed and therefore subject to the forces exerted during stormyconditions. These exceptional forces can cause deterioration of the mooringlines and in some circumstances result in mooring line breaks. This has obviousimplications for personnel, asset and environmental safety.
Being able to monitor the tension experienced by the mooring lines enables FPSoperational personnel to proactively take the required measures to maintainmooring line integrity. This paper details the design and installation of a newmooring line monitoring system allowing such mooring integrity monitoring on a FloatingProduction Storage Offloading (FPSO) vessel operating offshore Brazil.

Introduction
SBM supplied the FPSO for deployment in Brazilian waters. The vessel is mooredusing 9 mooring lines bundled in 3 sets of 3 lines at 120° from each otheraround the turret chaintable.
A new mooring line monitoring system was specified for this project. Thepurpose of the system was not only to notify the operations team in the eventof a line break but also to record the line tension experienced over time sothe mooring line performance could be evaluated. The project specification also called for thesystem to have the capability to identify progressive degradation such as linecreep and quantify the need for line retensioning.

Technical Challenges
Many of the systems used in the past to monitor anchor leg load have offeredlimited reliability. Load cells need to be mounted in the load path which leadsto difficulties when maintaining them. Shear pins require modifications to thechain which can affect chain integrity. Strain gauges have issues with water leakage. Moreover the cables required to connect these sensors to the data collectionsystem could become trapped and severed during a subsea intervention like riserpull-in.
When developing the system reliability and robustness was foremost in thespecification. Therefore Pulse decided to use inclinometers in the developmentof the system. An inclinometer was attached to the chain hawse of each leg. This meant that the sensor was outside the load path, enabling straightforward maintenance ofthe sensor. Furthermore, each anchor leg chain can be pulled through the chainhawse to re-tension the chain without affecting the operation of theinclinometer.
In order to avoid the problems associated with cables connecting the system, Pulse used acoustic communication to relay the measured data to the controlroom. Figure 1 shows the type of acoustic receiver used.
Ocean Current from 500 to 1000 Meters in the Gulf of Mexico
Authors: Fan Shejun , Harington-Missin Liam , Oey Lie-Yauw , Guan Xiaorui Amy , Eltaher Ayman 
Published: April 2012

Abstract
As part of the Bureau of Ocean Energy Management, Regulation and Enforcement(BOEMRE) sponsored study for ocean current monitoring from 500 - 1,000 metersin the Gulf of Mexico, this paper describes the methodology and results ofassessing the characteristics of the forcing and occurrence of elevated currentevents.
BOEMRE NTL ADCP data, historical mooring current data and three types ofPrinceton Regional Ocean Forecasting System (PROFS) model data were used forthis study. Based on the analysis of current characteristics, ocean currentkinetic energy distribution and observational data availability, fourrepresentative zones are indentified. For each zone, the long term and eventcurrent profile characterizations and subsurface elevated event screening areundertaken, and long- and short-term full water column current profilecharacterizations (representative current profiles and associatedprobabilities) are derived from selected quality controlled NTL ADCP data, historical mooring data and PROFS model data. These current profiles andspecific riser models for each type (Drilling, SCR, TTR, Hybrid Risers, and TLPTendons) are used to assess the VIV damage, which is documented in theaccompanying paper by Ozturk et al. (OTC 23570).
This study will evaluate the significance of ocean currents in water depthsbetween 500 and 1000 meters on riser and mooring systems, as well as toidentify whether any significant events have resulted. The study results willhelp BOEMRE to define whether monitoring below 500 meters is justifiable inregards to fatigue analysis of riser or mooring systems.

1. INTRODUCTION
Safe and efficient exploration and development of deepwater offshore oil andgas fields require the development of a comprehensive knowledge of the localoceanographic current regime. The study of ocean current monitoring from 500 -1,000 meters in the Gulf of Mexico was sponsored by the Bureau of Ocean EnergyManagement, Regulation and Enforcement (BOEMRE) of the U.S. Department of theInterior. The purpose of this study was three-fold:Assess the characteristics of Gulf of Mexico current forcing in the 500 to1,000 meter range and occurrence of elevated events;To evaluate the significance of ocean currents in water depths between 500and 1000 meters on the fatigue and design of risers, moorings and TLPtendons;Based on the findings, to form a recommendation on whether monitoring below500 meters is justifiable in regards to fatigue analysis of riser or mooringsystems.
This paper describes the activities associated with the first purpose of thestudy. The accompanying paper by Ozturk et al. (OTC 23570) addresses theremaining goals.
Dynamic Stresses and Fatigue Evaluation of Wind Turbines
Authors: Jafri Syed M. , Eltaher Ayman , Jukes Paul 
Published: April 2012

Abstract
Wind turbines and renewable energy devices are important components for thefuture of energy sector. This is due to fast depleting sources of oil and gasall around the globe. Offshore wind turbines offer numerous advantages, due totheir remote location from land, thereby reducing noise, higher power output(due to large wind speeds) and utilization of existing offshore platforms fortheir installation and operation.
This paper presents a general analytical solution for calculation of dynamicbending stresses induced in a wind turbine tower as a result of rotatingimbalance in the rotor blades. The formulation is based on elastic beam theory, with inclusion of rotating imbalance forces. The formulation neglects the bladegyroscopic effects and models only the lateral tower vibrations.
The dynamic stresses are highly important for fatigue evaluation of the steelwind turbine towers. The formulation models the linear elastic response of thetower under the effect of rotor imbalance, and proceeds to compute the dynamicbending stresses as a result of lateral vibrations. The model also includes theeffect of linear viscous damping at the rotor-nacelle at the top of tower, andshows the beneficial effect of damping to suppress vibrations and reducebending stresses. The damping may arise from sources such as aerodynamic dragand internal steel structural dissipation. The motivation of this technicalpaper is to provide a simple analytical desktop tool for an engineer toevaluate the dynamic stresses for a given wind turbine size (tower height, diameter, wall thickness, blades and nacelle mass, rotating imbalance androtational speed), for an initial dynamic stress and fatigue screening, beforeproceeding to perform more comprehensive aero-structural finite element modelsof the wind turbines for simulating the dynamics of the wind turbines.
An ROV-Deployed Deepwater Subsea Sampling System
Authors: Kelner Eric 
Published: April 2012

Abstract
The increase in deepwater production in the Gulf of Mexico and other locationsaround the world has brought a corresponding increase in the use of subseamultiphase flow meters. The placement of subsea multiphase flow meters near thewells provide improved reservoir management, well diagnosis, allocation, aswell as oversight for safety. However, to realize their full potential, multiphase flow meters require timely and accurate fluid properties at meterconditions. Subsea architectures with long flow lines and risers have led tothe realization that well tests and topside samples cannot meet the needs ofthis new measurement technology.
A method for ROV-deployed subsea sampling has been developed in conjunctionwith several major operators to provide a means to capture representative fluidsamples at the multiphase meter or other locations, at various times throughoutthe life of the well. The system has been tested in a high-pressure flowlaboratory, as well as in a tank, to simulate ROV deployment in deepwaterconditions. A significant feature of this sampling system is its proposal of astandardized interface. Making such an interface between the sampling systemand the process fluid available to manufacturers will relieve them from thecosts and complications of developing proprietary systems, with varied designsand procedures. Furthermore, users will have more choices of both equipment andROV vendors, since these components should be interchangeable. This paper willpresent an overview of this sampling system development and some of itsperformance characteristics.

Introduction
The increase in deepwater production in the Gulf of Mexico and other locationsaround the world has brought a corresponding increase in the use of subseamultiphase flowmeters. The placement of subsea multiphase flowmeters near thewell provides improved reservoir management, well diagnostics, and allocation. However, multiphase flowmeters require timely, accurate fluid properties, atmeter conditions, to realize their full potential. Subsea architectures withlong flow lines and risers have led to the realization that well tests andtopside samples cannot meet the needs of this new measurement technology.
A method for a remotely operated vehicle (ROV)-operated subsea sampling systemhas been developed to provide a means to capture representative fluid samplesat the multiphase meter and other locations at various times throughout thelife of the well. The system has been tested in a laboratory and a tank tosimulate ROV deployment in subsea conditions.
One attractive feature of the sampling system is the proposed standardizedinterface. A standardized interface between the sampling system and the processfluid will relieve users and manufacturers from the costs and complications ofproprietary systems with varied designs and procedures. The standardizedinterface will be made available to interested parties. This paper presents anoverview of the sampling system development and testing.
The Belly Spar - Design and Verification of an Ultradeepwater Solution
Authors: Loken Rolf , Laukeland Lars , Hannus Henrik 
Published: April 2012

Abstract
The Spar platform has developed into a well functioning solution for Gulf ofMexico environment. Considering use of this solution in the North Atlantic, themetocean conditions differ by long period swell and fatigue induced by normaloperational seas.
In order to meet these challenges, it is desirable to consider a classic Sparthat is more fatigue redundant than a truss, but the swell requires highnatural periods, to avoid parametric heave-pitch resonance.
A new version of the Spar in response to these requirements is the Belly Spar. It can be considered as a classic Spar with a Belly; starting below the wavesurface and extending down to the hard tank depth. A concrete Spar concept withreduced waterline diameter has also been developed by Aker Solutions for arcticapplication. This concept had the dual benefit of increasing the natural periodin heave as well as reducing the ice load from sea ice
The concept has been developed for a field in the Norwegian Sea, in water depthof 1,200m (4,000ft). The hydrodynamic analyses show excellent performance, however contain assumptions on damping. The design has been by model testing ofthe design in wave and current combination representing 10,000yr events, asshown by results and correlations in the paper.
The design opens up new areas for the Spar platform, with good motions that canaccommodate steel catenary and top tensioned risers. As for previous Sparconcepts, the application is in deepwater and ultradeepwater.

Introduction
The use of the Spar structure for oil and gas production was conceived byEdward Horton in the 80ies, ref. 1. As the first project was realized, Aker gotinvolved in the design and delivery, ref. 2. With subsequent projects cameexperiences and new design variants were developed, the truss Spar was the"next generation" and the cell Spar has been another variant.
The use of the Spar has been limited to the Gulf of Mexico (except for one inMalaysia), with certain metocean conditions, mostly mild weather, butoccasionally a loop current or hurricane event. During a hurricane, theplatform is shut down and the personnel are evacuated.
When considering applications in other parts of the world, the local conditionsneeds to be considered, which may yield changes to the design. Previousevaluations in use in regions with swell have observed challenges with motionresponse. The option for reducing the water plane area by a reduced topdiameter was implemented already in 1976 for the Brent Spar loading buoy andthe influence on the motions thoroughly documented by Haslum, ref. 3.
The truss of a truss spar has been seen as a means of reducing the weight ofthe midsection, between the hardtank and the ballast. However, the trussconcentrates the load path into critical components without redundancy that puthigh requirements on the fatigue design. An alternative means for reducing theweight is to reduce the diameter, relative to the hard tank.
Robotic MFL Sensor and Vibration based Deepwater Riser Monitoring System
Authors: Huang C , Nagarajaiah Satish 
Published: April 2012

Abstract
The safety of deepwater risers is essential for successful operation ofoffshore platforms. In this paper, new structural health monitoring (SHM)techniques for deepwater risers is developed to monitor damage due to vibrationand fatigue. The global monitoring is achieved using the proposed blindidentification technique based on vibrations. First, the location of thefatigue damage is determined by the proposed blind identification technique. The global monitoring is used to identify the dominant modes of vibration, fromwhich, the likely location of fatigue damage is estimated. The proposed methodis validated using Gulfstream test data from MIT. Second, extent of damage isdetermined by local monitoring using robotic crawler with magnetic flux leakage(MFL) sensor. The effectiveness of the local monitoring with MFL sensor isverified by experiments.
Combining the proposed global and local monitoring techniques can enhancefatigue damage estimation. Local inspection using MFL sensor is power efficientand yields high resolution results that can estimate the extent of damage. Proposed fatigue damage estimation technique can satisfactorily predictlocation of global damage.
The proposed SHM techniques are for well suited for deepwater risers. RoboticMFL sensor can be used for in-line inspection for pipelines. Proposed fatiguedamage estimation method can be adapted to other offshore floatingsystems.

Introduction
Risers are the most important components of offshore oil platforms. Risers arethe conduits between a subsea wellhead and a drilling or production platformfor development, production, gas lift or water injection. They can be eitherrigid or flexible. Risers can be further classified as top tensioned risers(TTR), steel catenary risers, flexible risers and hybrid risers.
Mistakes in offshore oil production can be costly; in particular riser failurehas more severe consequences. Any failure incident in the riser would not onlybe an economical and environmental disaster, but also have far reachingconsequences affecting communities. The most recent and severe accidenthappened on April 20, 2010. The Deepwater Horizon, a semi-submersible mobileoffshore drilling unit, experienced a blowout. Deepwater Horizon sank on April22, 2010 and its associated riser collapsed with the platform. 11 workers diedin the explosion. An oil leak ensued from the drill site, which leaked 4.9million barrels of oil into the Gulf of Mexico, making it the largest oil spillrecorded in U.S. history [1] (largest of its kind in the world history [2]). Although disasters of this magnitude are the result of multiple failures, advanced monitoring can be of assistance in detecting such a blowout before itoccurs. SHM systems for risers in offshore deepwater platforms are needed todetermine whether there is damage and to activate contingency plans ormechanisms to initiate damage protection measures or repairs to preventcomplete failure.
Emergency Supply of Subsea High Pressure Control Fluid Six Shooter
Authors: Lazar Stephen , Shanks Earl F. , Wacasey Brandon 
Published: April 2012

Abstract
An overview of the design and functionality of the Oceaneering subseaaccumulator or Six Shooter is provided. The Six Shooter was developed as asolution to the historical challenges of BOP emergency intervention. ROVtooling for subsea Blowout Preventer (BOP) intervention has been limited tosmall hydraulic pumps which require substantial amounts of time to operate BOPrams. With faster closing times recommended for emergency intervention, supplementary accumulated volume is required subsea. The Six Shooter can belaunched from a support vessel, IMR vessel or Rig, eliminating the need forcostly Rig or BOP modifications. The unit can be deployed onto a customdesigned mudmat or an existing structure.
When deployed, the Six Shooter would allow a ROV (Remotely Operated Vehicle) ofopportunity to function and provide high flow (100 gpm) and pressure (5000 psi)to the BOP via a flying lead. At these flow rates, the industry standardspecifications of 45 second ram closures can be obtained.
Equipped with dual regulators, the output pressure of the Six Shooter can beselected with the turn of a ROV valve. Depending on the number of BOP functionsthat need to be closed during an emergency situation, additional units can beeasily added with standard high flow flying leads to increase the usablevolume. The subsea accumulators are constructed with materials that allowdependable and repeatable functioning over long exposures to a subseaenvironment.

Introduction
Industry standards continue to become more stringent and require a secondarywell control system that can be accessed by the ROV, (Remotely OperatedVehicle) and is able to close critical rams in less than 45 seconds. ROV pumpsare not capable of producing the combined flow and pressures required, therefore a high pressure, high volume system is required. One option might bea complete secondary set of accumulators mounted to the BOP and controlledsubsea. However, there are restrictions on the weight of the BOP stack, andthis solution is not suitable in many cases.
Therefore, a modular independent accumulator system that can be launched andtemporarily parked on the sea floor during a drilling campaign is ideal. Thisflexibility allows the operator to forgo costly modifications to the BOP stackand drilling rig. Oceaneering has designed and built an independent subseaaccumulator system that can be deployed onto a subsea structure (mudmat, pile, existing structure, etc...) and connected to the BOP via ROV. The Six Shootercan override functions in the event topside communication is lost on the rig. This unit can be launched from a support vessel, IMR vessel, or Rig allowingany ROV of opportunity to function it. Closing times with this equipment canmatch the closing times of the original BOP stack design specifications. TheSix-Shooter module is constructed with materials that allow dependable andrepeatable functioning over long exposures to a subsea environment.