bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Advances in Post-Installed Subsea Monitoring Systems for Structural and Flow Assurance Evaluation
Authors: Asgharzadeh Shishavan Reza , Brower David V. , Hedengren John D. , Brower Alexis D. 
Published: September 2014

An overview of fiber optic sensors for temperature, pressure, strain, and fatigue of subsea structures is provided. Current progress details efforts to ensure proper installation and bonding to existing risers, flow-lines, mooring lines, trees, and other structures in actual subsea environments. Developments include clamp prototypes, bonding techniques, long-term fatigue analysis, sensor calibration, and temperature compensation.
Fiber optic technology in subsea monitoring began over 20 years ago by migrating expertise from decommissioning of rocket motors. The first installations were on new installations of subsea pipelines, production risers, and drilling risers to measure strain and vibration for fatigue life monitoring. Of particular interest for these systems were detecting riser vortex induced vibration and strain throughout the touchdown zone. A prior limitation was that sensor installation was only performed top-side on new subsea equipment. This recent work demonstrates the capability to deploy on existing subsea equipment.
The novel contributions of this study are the developments that optimize the clamp design, bonding techniques, and factors that allow long-term service life. Button pull tests validate long term service life after the clamps are subjected to accelerated aging tests. Details on the subsea calibration also provide insight on the recent progress with post-installed sensors.
The purpose of reliable post-installed advanced sensors is not only to detect failures of subsea infrastructure but also to warn of signs of fatigue or hydrate formation that contribute to catastrophic failures. The calibration and testing mentioned in this paper are part of the Clear Gulf study, a collaboration formed in 2010 between the offshore energy industry and NASA. The study continues to make advances in highly sensitive monitoring systems that anticipate failures, catastrophic events, and flow assurance issues.
Ice Nonsimultaneous Failure, Bending and Floe Impact Modeling for Simulating Wind Turbine Dynamics Using FAST
Authors: Yu Bingbin , Karr Dale G. , Sirnivas Senu 
Published: September 2014

Many promising locations for developing offshore wind energy are in cold regions. This type of environment introduces one important technological challenge for offshore wind turbine design: the impact of floating surface ice. Recent developments to add an ice-loading module to the wind turbine computer-aided-engineering tool FAST are described in this paper. These efforts enable FAST, developed and maintained by the National Renewable Energy Laboratory, to simulate the impact of ice on offshore wind turbines. The ice-loading module includes different ice mechanics models that address various ice properties, failure modes, and ice-structure interaction mechanisms. In a previous OMAE symposium paper, models for quasi-static crushing, transient dynamic ice breakage, and random forcing for the ice module were described.
In this paper, three new models are presented. One model evaluates the ice-loading effective pressure reduction caused by ice nonsimultaneous failure in discrete local zones across the contact area. The second model generates time-dependent ice forces on conical structures caused by bending failure. The third model is used to simulate large ice floe interaction with wind turbine support systems. This third model describes ice forces that are limited by momentum or splitting failure of ice floes. These models are integrated in the FAST modularization framework and allow for the simulation of coupled ice force, ice floe motion, and wind turbine structure response. This paper also presents example numerical simulation results of wind turbine dynamics using FAST coupled with these three new models.
Ocean City Planning in the Waters of Okinotorishima
Authors: Watanabe Yoshiyasu , Yoshida Koichiro , Nambara Takeshi 
Published: September 2014

Okinotorishima is the Japanese southernmost tropical island and has the exclusive economic zone (EEZ) of about 430,000km2 area. It is located approximately 1,700km away from Tokyo and 1,100km away from Okinawa and consists of a coral reef of 7.6km2 area and two islands within the reef. In the waters of Okinotorishima, sea bottom mineral resources such as manganese nodule and cobalt rich manganese crust, biological resources such as fish and renewable energy resources such as ocean thermal energy conversion (OTEC), wind force and solar power are promising.
The objective of this research is to propose an OCEAN CITY Planning to administrate and utilize Okinotorishima and its surrounding waters (EEZ) and to report the development of mechanical connector, which is a key technology to construct the OCEAN CITY in its waters. In the OCEAN CITY, economic activity, research and development (R&D) activity and sightseeing/leisure activity are performed based on the resources mentioned above. The proposed OCEAN CITY consists of a semisubmersible floating ring structure and a semisubmersible floating rectangular runway. The ring structure and the runway are constructed with mechanically connected multiple floating units of about 300m length each. Both semisubmersible structures are also connected by mechanical connectors. In this paper, it is shown that the OCEAN CITY can produce electricity, water and food for the use in the city and for the sale outside the city. It is also shown that the mechanical connector, which is indispensable for very large floating structures such as the proposed OCEAN CITY used in open seas, has been promisingly developed.
Drifting Time of a Standard Drillship
Authors: Teixeira Fernando J. R. , Oshiro Anderson T. , Tannuri Eduardo A. 
Published: September 2014

This paper presents a methodology in order to perform a drift off calculation for drillships according to given parameters such as: environmental conditions and water depth. Drift off occurs when there is insufficient thruster force so that the vessel is drifted away from the target position by the environmental forces. For a safe operational drillship it is expected that the drifting off will be resumed in due time when blackout recovery system starts running and, therefore, enough thrust takes place. Water depth plays an important role when considering the default maximum release of Lower Flex Joint (LFJ) angle for physically disconnecting, which is 10 degrees in the majority of suppliers. This methodology is intended to be applied to drillship design, by comparing the time to stop drifting and the distance from the reference point after a total blackout occurs.
Electrical generators sets installed in drillships are designed to work with extreme environmental conditions. Since there is an excess of installed power for the majority of the operational time, drillships often operate with all high voltage busbars connected to each other improving engine efficiency, decreasing levels of pollution emissions and reducing maintenance. The use of this electrical power configuration is possible because there is no need to turn on all generators at the same time, but only the ones that are needed on that particular moment. However, when a single failure such as a short circuit occurs and the system is not prepared to disable and segregate the failure, all electrical system will crash, causing a total blackout and the drillship will start to drift off.
The drifting off time was obtained by numerical simulations conducted by modeling a standard drillship using time domain software. The model took into consideration the vessel hydrodynamics under environmental conditions (wind, current and wave), the drag force in marine drilling riser, and the thrusters in Dynamic Positioning (DP) operation.
The simulation is divided into three steps: First, the behavior of the DP system in full operation is simulated until system is stable. After that, all thrusters are turned off to simulate a total blackout. Finally, since the ship will not stop immediately because of its inertia, a time range for the ship’s inertia was also considered and this time is added to the pre-established blackout duration.
The conclusion of the study shows how parameters as water depth, environmental conditions, and blackout recovery time affect the necessary time to stop drifting off, so as to foresee that after a total blackout the standard drillship will remain in safe limits.
Mooring System Monitoring Using DGPS
Authors: Minnebo Joerik , Aalberts Pieter , Duggal Arun 
Published: September 2014

Over the recent years, the need for active monitoring of offshore production facilities has increased. Due to significant amount of mooring line failures in the recent past, permanent mooring systems for Floating Production Units such as FPSO’s, FSO’s and future FLNG’s are typically required to have active monitoring systems to provide feedback of the mooring system’s status, performance and integrity.
This paper will address some of the offered solutions with regards to active mooring system monitoring. Some pros and cons are given for several techniques within the industry currently available, and then a simple but elegant alternative is proposed. With the use of position monitoring, for instance with GPS signals, qualitative and quantitative feedback can be provided on the status of the permanent mooring system. A detailed explanation is given backed up by a few real life examples in which such a system was used to quickly assess the status of the mooring system.
Multiscale Finite Element Analysis of Unbonded Flexible Risers
Authors: Edmans Ben , Pham Dinh Chi , Zhang Zhiqian , Guo Tianfu , Narayanaswamy Sridhar , Stewart Graham 
Published: September 2014

Unbonded flexible risers are a key technology in existing and proposed offshore developments. With increasing water depth, the demands on risers increase and the design against hydrostatic and tension loads becomes more of a challenge. In addition, many existing subsea production systems are approaching the end of their design life and operators need to know if they can remain in-service.
To enable the benefits from deepwater production and life extension projects to be realized while minimizing risks to life, property and the environment, accurate modelling and analysis tools are required to improve the prediction of failure modes and to develop a better understanding of the conditions leading to progressive failure. In this work, a multi-scale approach is adopted whereby a global dynamic analysis model is employed to determine the overall displacements of the riser and this is linked with a local model that can provide accurate forces and stresses for the prediction of collapse, fatigue damage and buckling of tensile armour wires.
Firstly, we describe a nonlinear constitutive model for use in large-scale dynamic analysis of flexible risers based on an analytical homogenization of composite cylinders using the analogy between slip between pipe layers and plastic flow in continua. The model is able to reproduce the bending hysteresis behaviour observed in flexible pipes and its dependence on internal and external pressure. Secondly, we show a procedure for obtaining equivalent material parameters for this model from finite element local analyses of a flexible pipe. Finally, we show the implementation of this constitutive model in a riser system using two-dimensional co-rotational hybrid beam finite elements.
Application of CFD to Predict the Hydrodynamic Performance of Offshore Fairing Designs
Authors: Corson David , Cosgrove Steve , Constantinides Yiannis 
Published: September 2014

In this work, the hydrodynamic performance of various fairing designs have been investigated using Computational Fluid Dynamics (CFD). This paper is divided into two primary sections. The first section involves a thorough sensitivity study to investigate the parameters that are vital in establishing an accurate and robust CFD modeling approach for fairings. The parameters that were investigated during this phase of the work include the mesh density used in the simulations, the blockage ratio (i.e. physical size of the domain that is modeled), the Reynolds Number, and the geometric detail included in the simulations. Upon completion of the sensitivity studies, CFD “best practices” were established. These practices were then applied to a baseline fairing design, and the results were compared against available test data. The CFD approach was shown to predict drag coefficients that agreed with test data within 10% for all cases that were investigated.
The second section of this paper focuses on application of the CFD techniques to evaluate 3 candidate fairing designs. The designs differed in the length and taper angle of the fins. The effect of shortening the fins on straight fin cases had a minor impact on the resulting drag. However, a significant reduction in the drag on the fairings was observed when the fins were tapered inward.
Analytical Approach for Mechanical Responses of Spanning Pipelines
Authors: Bai Qiang , Duffy Brian 
Published: September 2014

An analytical analysis method for spanning pipelines with vertical imperfections under different loading conditions is presented. Analytical solutions for the pipe configuration, stress distributions, and contact reaction load to the crossed object are obtained under tensile or compressive axial loads by solving the governing differential equations. A comparison of this analytical method with the finite element method is carried out to evaluate the accuracy and consistency of the solutions. This analytical approach may be very helpful for obtaining preliminary results in a limited time without using the more time-consuming and expensive finite element method.
The analytical model accounts for the vertical pipe-soil interaction and drives the solution for the mechanical response of pipeline at the touchdown points of the spanning pipeline. Parametric analyses of the spanning pipeline are carried out to investigate the influences of the span length, vertical imperfection magnitude, and soil stiffness on the mechanical response of the pipeline.
A simplified analytical method for the span segment only is given to compare with finite element analysis. A correlation of dimensionless span length and dimensionless effective axial force is obtained based on the simplified analytical method for different vertical offsets and axial force (tensile or compressive load). The comparison results show that the simplified analytical method may be used as for a quick engineering calculation when the pipe soil-interaction is not clear.
Real-Time Software to Estimate Friction Coefficient and Downhole Weight on Bit During Drilling of Horizontal Wells
Authors: Tahmeen Mazeda , Hareland Geir , Aadnoy Bernt S. 
Published: September 2014

The increasing complexity and higher drilling cost of horizontal wells demand extensive research on software development for the analysis of drilling data in real-time. In extended reach drilling, the downhole weight on bit (WOB) differs from the surface seen WOB (obtained from on an off bottom hookload difference reading) due to the friction caused by drill string movement and rotation in the wellbore. The torque and drag analysis module of a user-friendly real-time software, Intelligent Drilling Advisory system (IDAs) can estimate friction coefficient and the effective downhole WOB while drilling. IDAs uses a 3-dimensional wellbore friction model for the analysis. Based on this model the forces applied on a drill string element are buoyed weight, axial tension, friction force and normal force perpendicular to the contact surface of the wellbore. The industry standard protocol, WITSML (Wellsite Information Transfer Standard Markup Language) is used to conduct transfer of drilling data between IDAs and the onsite or remote WITSML drilling data server.
IDAs retrieves real-time drilling data such as surface hookload, pump pressure, rotary RPM and surface WOB from the data servers. The survey data measurement for azimuth and inclination versus depth along with the retrieved drilling data, are used to do the analysis in different drilling modes, such as lowering or tripping in and drilling. For extensive analysis the software can investigate the sensitivity of friction coefficient and downhole WOB on user-defined drill string element lengths. The torque and drag analysis module, as well as the real-time software, IDAs has been successfully tested and verified with field data from horizontal wells drilled in Western Canada. In the lowering mode of drilling process, the software estimates the overall friction coefficient when the drill bit is off bottom. The downhole WOB estimated by the software is less than the surface measurement that the drillers used during drilling. The study revealed verification of the software by comparing the estimated downhole WOB with the downhole WOB recorded using a downhole measuring tool.
Viability of Fixed Riser Support Structures for Lazy S Riser Configuration in Shallow Waters
Authors: Labanca Edson L. , Ribeiro Elton J. B. , Medeiros Cipriano J. , Ferreira José A. N. , Gomes Victor P. , Amaral Renato D. C. , Mejia Oscar J. P. R. , Basilio Leandro P. , Noronha Neto Celso C. 
Published: September 2014

When in shallow waters, not only the risers, but also the structures and equipment are submitted to different conditions from the ones related to deepwater applications. OGX has developed offshore applications in shallow waters in Campos Basin, Brazil, using a FPSO with Lazy S riser configuration, based on the Midwater Arch systems (MWA).
MWA systems are feasible due to OGX application scenario, but they present some disadvantages, such as: high compliance of the buoyant section to the FPSO, large static offset (common issue in shallow waters applications), which makes the MWA carry the risers that are clamped at the top; high manufacturing and installation costs, associated to the high weight of the structure, which includes large and heavy buoys; limitation regarding transportation, sometimes requiring heavy duty trucks, and consequently, more expensive ones. These disadvantages could be avoided by using another type of support structure, but it depends on the application conditions.
Aiming to optimize the Lazy S configuration for new applications in shallow waters, a viability study of a most simplified concept of support, fixed and less compliant, was carried out considering as a standard scenario the Waimea field (under development), located in Campos Basin, Brazil. As a result of this study, OGX and Wood Group Kenny developed the conceptual project of an innovative design of Riser Support Structure (RSS).
Therefore, this paper addresses the technical challenges that were faced during the design of this new concept of Riser Support Structure for shallow waters in offshore applications, including issues regarding the required structural safe response and aspects comprising installation and some decommissioning considerations.
Regarding the design, this paper discusses the structural analyses performed to validate the RSS, which include VIV and Finite Element Analyses, presenting its main results, and the critical issues encountered during these analyses. They include issues such as: Overstress due to combined loads; stress concentration in important structural components; and stress concentration due to impact load (issue recognized during dynamic analysis to simulate the pile driving operation).
Application of CFD Based Wave Loads in Aeroelastic Calculations
Authors: Schløer Signe , Paulsen Bo Terp , Bredmose Henrik 
Published: September 2014

Two fully nonlinear irregular wave realizations with different significant wave heights are considered. The wave realizations are both calculated in the potential flow solver Ocean-Wave3D and in a coupled domain decomposed potential-flow CFD solver. The surface elevations of the calculated wave realizations compare well with corresponding surface elevations from laboratory experiments.
In aeroelastic calculations of an offshore wind turbine on a monopile foundation the hydrodynamic loads due to the potential flow solver and Morison’s equation and the hydrodynamic loads calculated by the coupled domain decomposed potential-flow CFD solver result in different dynamic forces in the tower and monopile, despite that the static forces on a fixed monopile are similar. The changes are due to differences in the force profiles and wave steepness in the two solvers.
The results indicate that an accurate description of the wave loads is very important in aeroelastic calculations especially in cases where the aerodynamic loads and damping are insignificant.
Dissimilar Metal Welding of Nitronic 50 HS® and 25% Cr Super Duplex Stainless Steel
Authors: Nissley Nathan , Anderson Timothy D. , Noecker Fredrick F. , Roepke Caleb , Gallagher Morgan , Hukle Martin 
Published: September 2014

High pressure tubing and associated tubing couplers are critical components required for the operational control of subsea oil and gas production equipment. Tubing couplers used in subsea oil and gas developments are commonly made from Nitronic 50 HS® (N50HS) due to its high strength, corrosion resistance, and resistance to galling. Nitronic couplers are typically welded to several dissimilar metals including super duplex stainless steel (SDSS) control tubing using SDSS filler metals such as AWS A5.9 ER2594.
Recent evaluations have found that sigma (σ) phase forms in N50HS weldments and its effect is not broadly understood by industry. During N50HS solidification, Scheil solidification conditions establish compositional gradients in the unmixed zone located along the fusion line adjacent to the N50HS base metal. This solidification-induced segregation promotes compositions that are susceptible to interdendritic intermetallic compound formation when they are reheated by subsequent weld passes such as in multipass welding or at weld start-stop locations.
Decreasing heat input is a common approach to reduce or eliminate the formation of intermetallic compounds in SDSS. Although decreasing heat input can reduce the amount of energy available to drive the solid state transformation from ferrite to σ, it does not change the solidification mode (AF) or solidification conditions from Scheil to para-equilibrium within the range of cooling rates possible with arc welding processes. As such, the compositional gradients that promote intermetallic compound formation along the N50HS fusion line can only be minimized through heat input control and cannot be eliminated in arc welds regardless of the heat input used.
The effects of σ on toughness and corrosion resistance of Nitronic weldments were evaluated. N50HS solidified samples with up to 2 volume percent σ were found to have CVN of >40J at −40°C, and no evidence of pitting at 25°C in the ASTM G48 test.