bluuebunny/crossref_metadata_2025 huggingface dataset:
Parallelized Element-by-Element Architecture for Structural Analysis of Flexible Pipes Using Macro Finite Elements
Authors: Geremias Toni Fernando , de Arruda Martins Clóvis
Published: October 2017

Flexible pipes are employed to transport oil and natural gas from the seabed to the floating units, and vice versa. These pipes are made of concentric layers of different geometries, materials and structural functions in order to withstand a series of static and dynamic loads from its adverse operating environment. The local analysis is an important stage in the design of a flexible pipe and consists in determining the stresses and strains distributions along its layers. Multipurpose finite element packages, such as ANSYS and ABAQUS, are commonly used in this task, but present many limitations for their generic nature, varying from the absence of specific tools for model creation to heavy restrictions of the number of degrees-of-freedom to make computational processing feasible. Over the past years, several macro finite elements were formulated by PROVASI & MARTINS specifically for modeling a flexible pipe, allowing a reduction in the total number of degrees-of-freedom. However, until the present moment, there is no parallel processing software that efficiently implements these elements for large model applications. Aiming greater computational performance, the macro elements can be combined with the element-by-element (EBE) method, which is characterized by the global stiffness matrix elimination, is highly parallelizable, scalable and shows a memory consumption that grows linearly with the number of elements in the model. In this context, a parallelized architecture for structural analysis of flexible pipes that explores the EBE method and macro finite elements has been developed, being of great interest for design applications in the industry.
Initial Design of a Double Curved Floating Bridge and Global Hydrodynamic Responses Under Environmental Conditions
Authors: Wan Ling , Magee Allan Ross , Hellan Øyvind , Arnstein Watn , Ang Kok Keng , Wang Chien Ming
Published: October 2017

In this paper, a floating bridge concept is proposed. This bridge concept comprises a two oppositely curves in plan, which enables the cancellation of the axial forces at the bridge as one arch will be under compression while the other arch is in tension due to environmental forces acting in one direction. The road deck is carried by truss structures that are kept above the water by several elliptical cylindrical pontoons. To reduce drag load, the cross sectional area facing the current is reduced as much as possible, while the buoyancy is kept the same based on the initial weight estimation. Initial design consideration and methodology of a double curved floating bridge is presented, and a numerical model is established for analyzing this concept. Hydrodynamic and structural dynamic aspects are included in the numerical model. Parametric study of the bridge structural rigidity is performed to investigate the effect to the responses. White noise, regular and irregular wave simulations are carried out to investigate the dynamic responses of the floating bridge under different conditions.
An Experimental and Numerical Investigation of the Effect of Axial Thermal Gradients in Flexible Pipes
Authors: Fergestad Dag , Klæbo Frank , Muren Jan , Hylland Pål , Grøv Tom Are , Lange Hans , Gjøsteen Janne K. Ø. , Gjendal Andreas , Melve Bjørn , Kristensen Claus Egebjerg
Published: October 2017

This paper discusses the structural challenges associated with high axial temperature gradients and the corresponding internal cross section forces. A representative flexible pipe section designed for high operational temperature has been subject to full scale testing with temperature profiles obtained by external heating and cooling. The test is providing detailed insight in onset and magnitude of relative layer movements and layer forces. As part of the full-scale testing, novel methods for temperature gradient testing of unbonded flexible pipes have been developed, along with layer force- and deflection-measurement techniques. The full-scale test set-up has been subject to numerous temperature cycles of various magnitudes, gradients, absolute temperatures, as well as tension cycling to investigate possible couplings to dynamics.

Extensive use of finite element analysis has efficiently supported test planning, instrumentation and execution, as well as enabling increased understanding of the structural interaction within the unbonded flexible pipe cross section. When exploiting the problem by finite element analysis, key inputs will be correct material models for the polymeric layers, and as-built dimensions/thicknesses. Finding the balance between reasonable simplification and model complexity is also a challenge, where access to high quality full-scale tests and dissected pipes coming back from operation provides good support for these decisions.

Considering the extensive full scale testing, supported by advanced finite element analysis, it is evident that increased attention will be needed to document reliable operation in the most demanding high temperature flexible pipe applications.
Consistent Free Span VIV Fatigue Analysis of Flexibles
Authors: Caruso Mário , Han Xu , Sødahl Nils
Published: October 2017

The fatigue life assessment of free spanning flexible products, such as subsea cables and umbilicals, due VIV requires special attention to the structural properties due to the stick/slip behaviour of helix elements in bending. Essential parameters for assessment of stick/slip effects in free span VIV response are the structural damping in the stick regime (i.e. umbilical behaves as a solid cross section due to friction between the helix elements) as well as the additional damping introduced by the hysteretic damping due to the stick/slip behaviour in bending. Furthermore, consistent fatigue stress recovery considering the stick/slip behaviour in bending is essential for fatigue life predictions.

The consistent evaluation of stick/slip behaviour requires more sophisticated calculation procedures due to the non-linearity it introduces. Hence, industry practice has been to consider simplified, linear calculation procedures. However, future flexibles utilization may be much benefitted by a consistent stick/slip treatment in free spanning VIV fatigue assessments, as it may allow for longer allowable free span lengths or longer fatigue life.

The overall objective of the paper is to establish a consistent free span VIV analysis methodology for flexibles in compliance with requirements given in ISO 13628-5 ‘Subsea Umbilicals’ and the overall philosophy of DNV-RP-F105 ‘Free Spanning Pipelines’.

A consistent fatigue analysis scheme for VIV in free spans is outlined using commercially available state-of-the-art computer programs for free span VIV response analysis (FatFree) and cross section stress analysis (Helica). The performance of the calculation scheme is demonstrated by case studies in a complex long-term current loading environment. It is shown that consistent treatment of the mechanical properties of flexibles is essential for VIV fatigue life assessments of free spans.
Through-Life Reliability Design of Light HP/HT Pipelines on Soft Sloping Seabed With Buckling, Anchoring and Route Bend Stability Issues
Authors: Maschner Emil , Wang Yunxiao Nick
Published: October 2017

Some recent projects have required pipeline routings from cluster wells to platforms or FPSOs along undulating seabed with lengthy route bends, escarpment and change of slope features. The operational in-place stability of the relatively light insulated pipelines was the primary design concern, and was compounded by interactions between seabed induced global buckling and pipeline walking due to significant seabed slope. In addition, onerous weld defect criteria limited the extent of allowable bending to which the HP/HT pipelines can be subject during their through-life operation. This necessitated the development of reliable planned buckle schemes which would work with periodic pipeline anchors placed along the lengths of the routes of these pipelines to control walking and associated bend and planned buckle pull-out during routine start-up/shutdown operational cycles. Pipe-soil interaction guidance such as SAFEBUCK and project-specific pipe soil testing results had significant influences on realistic simulation of through-life in-place stability. A state of the art reliability tool was developed for these projects based on guidance available in the public domain and the characteristic 3D global buckle formations evident along operational pipelines with a significantly undulating seabed.
Seismic Design of Jumpers: The Coupling Conundrum
Authors: Cademartori Marcello , Zanoli Omar , Parker Eric J.
Published: October 2017

Subsea developments in seismically active areas present a number of engineering challenges. One such item, which is frequently underestimated, is design of jumpers to resist earthquake loading. Jumpers connect quite dissimilar pieces of subsea equipment, for example heavy manifolds on deep foundations, PLETs on mudmats and wellheads supported on slender well casings. If the structures connected have a different dynamic response (e.g. manifold, PLET and wellheads with different fundamental periods), the jumpers receive additional loads from the out of phase structure movements. Such “seismic coupling” is particularly an issue for high pressure high temperature (HPHT) fields, where stiff heavy jumpers are combined with large manifolds. This paper discusses possible approach to evaluate coupling, and provides practical advice for subsea designers. Specifically we address coupling from a point of view of the fundamental period of the connected structures and jumpers, making reference to results of dynamic modeling and codified experience from nuclear power plant design. Differentiation between cases which require fully coupled treatment, and those in which a more straightforward separation and analysis of the individual subsystems is very important to producing an efficient design in reasonable time frame. These aspects are illustrated using a case history from our project files.

Coupled dynamic analysis of primary (supporting) and secondary (supported) systems may not be always feasible or desirable. The number of supported structures may be such that a coupled analysis may create computational difficulties. In addition to this, data regarding the secondary system may be not available at the time of the analysis of the primary system with the result that development of a coupled model would be not applicable.

In cases where an attempt is made to develop complex coupled systems, sanity checks of such a system may be not an easy task. For these and other reasons, complete analysis of complex coupled systems is rarely performed. The objective of this paper is to explore the conditions under which an uncoupled analysis is justified and to give simplified indication to check the results of coupled models.

The paper presents a case study of a manifold-jumper-PLET. The system is evaluated using a standard uncoupled approach in which seismic actions are computed for the manifold, jumper and PLET considered as separate structures. The resulting actions are compared to those from a “coupled analysis” in which the full system is analyzed. The standard uncoupled analysis is found to be unconservative in cases where the jumper’s natural period of vibration is similar to that of the manifold or PLET. This approach shows promise as a means of identifying cases where coupled analysis is required to correctly assess seismic forces.
Subsurface Ice Transport at a Transversally Towed Ship Model
Authors: Zhou Li , von Bock und Polach Rüdiger U. Franz , Bai Xu
Published: October 2017

The subsurface transport of ice along the underwater body of a ship hull or a structure may cause damages to appendages. In order to investigate the conditions under which the ice accumulation occurs, a series of model tests was carried out in the ice basin of Aalto University. The used ship model was towed laterally against the ice with one side breaking level ice. The transport of broken ice floes broken off from the intact ice sheet has been has been monitored with underwater cameras. Both the model drift speed, respectively the ice drift speed, and the ice thickness are found to affect ice accumulation process. The Densimetric Froude number is introduced as measured to determine whether ice floes will accumulate on the upstream of the hull. It is found that ice accumulation is triggered at relatively low Froude number.
The Impact of Diagenesis and Compaction on Drilling Failure Detection
Authors: Mamat Nur Suriani
Published: October 2017

An important problem during drilling operation is wellbore instability; a complex problem caused by mechanical and chemical related factors. Even the best drilling practice could evade small instability problems that later may become irreparable. The risk of wellbore stability is mostly related to drilling, tripping and reaming activity with, including lost circulation, sloughing repair and loss of penetration. In this paper, the impact of historical and state of diagenesis and compaction on borehole instability has been studied, systematized, and used for general modelling. All the concepts are presented as symbolic concepts in a hierarchical order and linked in a chain of cause-effect relationships to wellbore failures. Through surveillance of drilling parameters, diagenesis and compaction were identified through formation hardness, well depth, shale type, and cuttings/cavings characteristic. From the analysis, kaolinite, which normally exists in intermediate diagenesis, is most likely to cause bit balling when hydrated. Smectite, which is water-sensitive clay, would cause chemical wellbore instability in water-based mud. Carbonates formation such as dolomite and limestone is more likely to result in lost circulation as compared to shale. Our work demonstrates how state of diagenesis and compaction could influence wellbore instability condition. This knowledge could be applied to understand the behavior of rock formation being drilled and would influence the prediction of probable failures as an end result. The method presented here integrates theoretical knowledge and real-time drilling data to envisage the most likely failure.
1:52 Scale Testing of the First US Commercial Scale Floating Wind Turbine, VolturnUS: Testing Overview and the Evolution of Scale Model Testing Methods
Authors: Fowler Matthew J. , Goupee Andrew J. , Allen Christopher , Viselli Anthony , Dagher Habib
Published: October 2017

Over the past 6 years, the University of Maine (UMaine) has been an active contributor in research and scale-model testing of floating offshore wind turbines (FOWTs). This paper serves to share the evolution of UMaine’s scale-model testing pedigree by exploring the various test campaigns at a high level, culminating with the design validation of the VolturnUS floating platform. These model test campaigns have each provided key insights into the behavior of FOWT platforms as well as improving the ability to perform model tests of FOWTs. In 2011, the UMaine-led DeepCwind Consortium carried out 1/50-scale model tests of a generic tension leg platform (TLP), a semi-submersible (semi), and a spar-buoy (spar) floating platform at the Maritime Research Institute Netherlands (MARIN) test facility. The designs were Froude-scaled and supported a scaled version of the 5-MW National Renewable Energy Laboratory (NREL) offshore research turbine. Data from these tests has been used extensively for numerical simulation validation efforts using NREL’s computer-aided engineering software FAST and laid the foundation for UMaine’s design efforts on VolturnUS. In 2013, UMaine conducted another test campaign at MARIN using the original semi-submersible from 2011 with an improved turbine as well as a 1:50-scale model of the VolturnUS concrete semi-submersible design. The improved DeepCwind semi-submersible data is currently being utilized in the validation of a large number of other analysis codes as part of the International Energy Agency’s OC5 project. In 2015, UMaine opened its own Wind/Wave test facility, the Alfond Wind/Wave Ocean Engineering Laboratory (W2). Utilizing this new facility, UMaine tested the 1:50-scale model DeepCwind semi-submersible, repeating the tests from MARIN, to validate the experimental equipment and procedures as well as demonstrate the capability of the W2. In 2016 UMaine carried out testing of a 1:52-scale model of the 100% design of the VolturnUS with a 6-MW topside as a final design validation to support the US Department of Energy-supported, full-scale Aqua Ventus demonstration project scheduled to be connected to the grid in 2019. A newly designed 6-MW scale model turbine was used in this test and the performance-matched turbine design methodology is described. Selected results from the test campaign and preliminary numerical comparisons are discussed as well as key lessons learned from the model test campaigns are presented.
Experimental Study of Hydrodynamic Responses of a Single Floating Storage Tank With Internal Fluid
Authors: Chi Zhang , Magee Allan R. , Ling Wan , Wang Chien Ming , Hellan Øyvind
Published: October 2017

When floating structure with internal fluid compartment is close to other structures, the multibody interaction problem needs to be addressed in addition to the internal fluid influence. Furthermore, shallow water effects become important, especially when the gap between the floating structure and the sea floor is small. These issues are encountered when designing a novel floating oil storage facilities in nearshore area. To investigate these issues, floating models under 1:50 scale are built to perform model tests.

The test set-up uses a set of flexible constraints working as fenders placed on frames to restrain the motions of the models in the horizontal plane. Various tests in waves are carried out to measure motion responses of single model in waves with different filling levels and stiffness of “fenders”. The reaction forces on the “fenders” are also measured. Several regular wave conditions are selected to perform tests on double model system to investigate multibody interactions under the influence of internal fluid and effects of waves between the tanks. The drag forces for both single model and double models are measured by performing model tests under constant current from different directions, to check the shielding effects. The tests are performed in shallow-water wave basin, and the constant currents tests are performed by towing the models in a flume tank. Both facilities are located at National University of Singapore (NUS).

This paper presents the detailed setting of the model tests. The single model’s RAOs with 20% filling level of internal fluid are given to demonstrate the influence of internal fluid on the motions. The performances of a single tank, including six DOF motions are shown. The results will be used for validation of numerical analysis results in the near future.
Verification Scheme for Unbonded Flexible Pipes: Definition, Implementation and Reflection of API 17J
Authors: Conti Fabien , Migeon François , David Aymeric
Published: October 2017

The present paper is related to the verification of unbonded flexible pipes designed and manufactured as per API 17J [1].

Back in the early nineties, in response to the needs of the industry for better quality, reliability and safety in unbonded flexible pipe products, Bureau Veritas established an innovative verification scheme relying not only on qualification testing, but also on the assessment of design methods, materials as well as manufacturing processes. This approach has proven particularly relevant considering several specificities of the flexible pipe industry: no ‘on-the-shelf’ design (each pipe being designed for project specific conditions), manufacturer specific local design methodologies, specific materials and manufacturing methods, high complexity and cost of testing.

This paper presents the verification methodology, its application as well as its ability to embody the latest normative requirements given in [1]. The specificity of the verification scheme, which consists in a breakdown between a Type Approval phase and a project phase, is also presented.
Installation of the Residual Curvature Method for Reeled Pipe in Pipe
Authors: Barnes Ross , McRae Angus , Rai Jitender , Abdelmageed Gareer
Published: October 2017

Current lateral buckling (LB) methodologies can be very expensive to implement and in some cases can have unsatisfactory trigger reliability. Imposing a designed Residual Curvature (RC) to provide an initiation point for lateral buckling, by appropriate modification to the straightener settings during reel-lay installation, is a relatively new and efficient method for LB initiation and has been applied in the field to single pipelines to date. The logical progression for this is to apply the RC methodology to the installation of reeled pipe in pipe (PiP).

PiP systems which are laid by reel-lay require detailed finite element analysis to determine vessel pipelay settings which ensure that the product is straightened as it leaves the vessel. In addition, imposing an RC section has further technical requirements over standard pipeline installation, i.e. meeting residual strain requirements over a specified length to deliver the required in-situ curvature needed for LB initiation. It is important to identify and optimise the solution to ensure that both installation and in-service requirements can be met and are practically achievable. Therefore, justification for use of the RC methodology for reeled PiP requires a portfolio of in-depth reeling and installation analyses to understand the application of this method for a complex reeled system, and how vessel and environmental influences may impact on the final solution.

To justify the implementation of the RC methodology for PiP, advanced non-linear FE analyses were used to assess vessel capabilities, the installation of PiP with RC and to determine the achievable in-situ RC for PiP. The effect and impact of reeling on the PiP is discussed in relation to both standard and RC pipelay. The paper discusses the technical challenges involved in the installation of an RC section for reeled PiP by presenting the methodologies employed in determining the achievable RC for PiP, the potential impact from environmental loading during installation and the resultant in-situ residual curvature that is expected.
Experimental Study of Push Coring Forces During Sediment Extraction Using a Robot Manipulator
Authors: Escudero José A. , Ramírez-Macías Juan A. , Correa Julio C. , Rozo David
Published: October 2017

This work addresses the experimental study of the forces exerted during the extraction of sediment samples using push corers. The study aims to measure push and pull forces under different deployment conditions for corer speed and coring depth using sand, sandy silt and silt as sediment. To guarantee a repeatable automated process, a KUKA KR6 robot manipulator was used to extract the sample. The forces were measured using a bidirectional S-type load cell. The required data is extracted from the robot’s internal variables log and from the load cell’s data acquisition system. The raw data is processed to develop simplified models for the forces using linear regression which are further analyzed and tested. Finally, the results obtained are discussed in the context of core sampling and practical conclusions are drawn from the experiments.
Iceberg Impact Simulation on Offshore Structures
Authors: Cahay Marc , Roberts Brian A. , Pike Kenton , Béal Pierre-Antoine , Septseault Cyril , Mravak Zoran , Benoit Claudie
Published: October 2017

In 2012 TechnipFMC, Cervval and Bureau Veritas initiated a common development program to offer a new tool for the design of offshore structures interacting with ice combining a variety of models and approaches.

This numerical tool called Ice-MAS (www.ice-mas.com) is using a multi-agent technology and has the possibility to combine in a common framework multiple phenomena from various natures and heterogeneous scales (i.e. drag, friction, ice-sheet bending failure, local crushing and rubble stack up). The current development phase consists of the determination of the forces generated by an iceberg during an impact on an offshore structure.

This paper will provide an overview of the latest Ice-MAS development. It will introduce the main functionalities of the simulation tool and the different options for modelling an offshore structure. It will then focus on the modelling approach used for an iceberg, the calculation of the different hydrodynamic coefficients and their variability according to the separation distance from the structure. The model used to compute the impact load will be detailed, including the local crushing behavior which is simulated by a pressure-area correlation.
Feasibility Study of the Floating Axis Wind Turbine: Preliminary Model Experiments
Authors: Akimoto Hiromichi , Iijima Kazuhiro , Takata Yasuhiro
Published: October 2017

Floating Axis Wind Turbine is a concept of a floating vertical axis offshore wind turbine. In this design, a vertical axis turbine is directly mounted on a rotating spar buoy so that it does not require mechanical bearing supports of the heavy rotor. Multiple roller-generator units are on another small semi-sub float for extracting power from the rotating spar. A water tank model of 1/100 scale 5MW turbine and model power take-off units of about 1/20 scale are used for checking the concept. The results show the stability of the proposed turbine and demonstrates the function of roller-generator units.
Holistic Energy Mapping Methodology for Reduced Fuel Consumption and Emissions
Authors: Lim Serena , Pazouki Kayvan , Murphy Alan J.
Published: October 2017

There are increasing concerns and regulations regarding the emission of pollutants from shipping. Therefore, regulations such as the Ship Energy Efficiency Management Plan (SEEMP) and Energy Efficiency Design Index (EEDI) have been made mandatory to cope with climate change concerns. To put these efforts into practice, the Energy Efficiency Operational Indicator (EEOI) was introduced in 2009 to account for the fuel consumption, distance travelled by the vessel and cargo mass. However, it is stated that these do not apply to ships that are not engaged in transport work such as research vessels and tugboats. These short sea shipping vessels have been neglected under current indexes and it is not possible for their properties to be quantified since current indices are for vessels carrying loads. The numbers of these specialised vessels are increasing in local waters, and are closer to coastal communities where concerns and impact from these pollutants would be more direct.

In the IMO greenhouse gas study, options for improving energy efficiency in terms of design includes the concept, design speed and capability, hull and superstructure, power and propulsion whilst the principle of energy efficiency in terms of operation includes fleet management, logistics and incentives, voyage optimisation and energy management. A reliable energy flow breakdown architecture and diagnostics for these smaller vessels is important and will contribute to an understanding of the energy production, distribution and consumption on-board. This feeds into the IMO plan to encourage energy management.

A systematic approach consisting of five distinct stages is recommended to accomplish a holistic approach for energy efficiency management. This includes understanding of energy flow breakdown architecture, vessel survey to understand operation and conduct, review existing sensors and new sensor installation, sensor communication and data processing, and finally data analysis. These stages are addressed in this paper to provide an overall understanding of a robust energy efficiency audit procedure and sensor matrix. This includes unifying the existing on-board sensors with the proposed new sensors for additional data collection where primary parameters are not readily available. Inferred secondary parameter calculations are also applied where direct data collection is not possible. This will allow information from the vessel to be transmitted to a common platform to enable detailed data analysis. The aim of this work is to improve energy management and monitoring, which leads to understanding and managing consumption of energy. A case study of this methodology has been carried out on the Princess Royal, a Newcastle University research vessel. Recommendations for further testing and optimisation of this methodology will be applied to tugboats and Offshore Supply Vessels (OSV).
Performance of OPT’s Commercial PB3 PowerBuoy™ During 2016 Ocean Deployment and Comparison to Projected Model Results
Authors: Parsa Kourosh , Mekhiche Mike , Sarokhan Joseph , Stewart David
Published: October 2017

This paper describes the validation process of a wave energy converter, the PB3, in support of achieving commercial ready status. The PB3 is a power and communication platform. It is a moored system which extracts useful electrical power from waves. The PB3 was developed for offshore remote autonomous applications such as the ones found in the oil and gas industry. Here, the results of full-scale ocean deployments of two PB3 PowerBuoys are reviewed in the context of final product performance validation, including power generation, and reliability. Furthermore, the Accelerated Life Testing of the PB3’s Power Takeoff (PTO) system is also discussed. A final Technology Readiness Level (TRL) is assessed based on API 17N TRL scale.
Hydrodynamics and Capture Efficiency of Plastic Cleanup Booms: Part II — 2D Vertical Capture Efficiency and CFD Validation
Authors: Dommergues Bénédicte , Brambini Roberto , Mettler René , Abiza Zaki , Sainte-Rose Bruno
Published: October 2017

To mitigate the growing impact of plastic pollution on marine ecosystems and global economy, The Ocean Cleanup (TOC) Foundation develops technologies to extract, prevent, and intercept plastic debris from coastal and oceanic environments. The core technology being optimized is the use of floating booms placed perpendicular to the main ocean plastic flow so it can concentrate plastic debris to a point where it can be extracted, shipped and processed in a cost-effective manner.

To investigate the capture efficiency of such a system, TOC conducted model scaled tests at the Dutch research institute MARIN. The objective of this paper is to present those tests along with the assessment of an hydrodynamic model and a CFD model to predict the dynamics of a rigid boom on one hand and the validation of this CFD model to predict the capture efficiency of such a boom.
Prevention of Alkali-Silica Reaction (ASR) in Light-Weight Wellbore Cement Comprising Silicate-Based Microspheres
Authors: Albers Dylan , Radonjic Mileva
Published: October 2017

Drilling through low pressure formations, either offshore or through depleted formations, requires the use of low density fluids to prevent lost circulation and as well as to properly place cement during cementing applications. Achieving these densities in cements can be done through foaming the cement, increasing water content, or through the addition of silica based microspheres. Each of these methods have individual limitations, and in the case of silica based microspheres, their specific fallback is a chemical instability with the microsphere itself reacting with the cement pore fluid.

This chemical instability creates a hydrophilic gel that is expansive and creates fractures in the cement as it expands, which is more formally referred to as alkali-silica reactivity (ASR). Prevention of ASR involves the application of additives to the cement that acts as a sink for the alkalinity in which prevents the expansion of ASR. A specific application that this paper investigates for this prevention is the use of Lithium nitrate.

This study looks at the effects of a high alkalinity environment onto the microspheres by visualizing the reactions that are occurring using Scanning Electron Microscopy (SEM), and confirming the presence of ASR when silica based microspheres encounter a high pH environment. Then cement samples were created to compare the effects lithium nitrate has on cements created with silica based microspheres. SEM and micro indentation was conducted on these samples, which showed that lithium nitrate prevents reactions, but after 28-day hydration a loss of mechanical properties is present.
Development of a Simulator Training Platform for Fish Farm Operations
Authors: Holmen Ingunn Marie , Thorvaldsen Trine , Aarsæther Karl Gunnar
Published: October 2017

The Norwegian aquaculture industry is accident prone compared to other industries and employees report a high number of near-accidents. Furthermore, escape of fish is a challenge for the industry. There is a potential for increased safety for both humans and fish if operators can practice operations in a safe environment. Existing simulators are not suited for this context.

This paper presents results from a research and development project aimed at developing a realistic simulator-based training platform for demanding fish farm operations. Three objectives guided the development process. First, a description of operations, aimed at identifying challenges and training needs, which formed the basis for selecting training scenarios well suited for aquaculture. Second, the development of mathematical models that could be used in the simulator were developed, and finally, a curriculum for training course modules to complete the platform. Platform thus points to the integration of the simulator and the practical and theoretical education of operators. In this article, the first and second part of the process are presented and discussed.
Experimental Investigation of Friction and Hydraulics in Circular and Non-Circular Wellbores With Oil Based Drilling Fluids
Authors: Taghipour Ali , Lund Bjørnar , Ytrehus Jan David
Published: October 2017

Borehole hydraulics, hole cleaning and mechanical friction are important factors for well planning and drilling operations. Many studies aim to exploit and optimize the effect of different operational parameters. The effect of wellbore geometry on hole cleaning and mechanical friction has so far not received much attention. This paper presents results from experimental laboratory tests where hydraulics, hole cleaning and mechanical friction have been investigated for circular and non-circular wellbore geometries with a relevant oil-based field drilling fluid (OBM). The non-circular wellbore geometry was made by adding spiral grooves to the wellbore walls in order to investigate the effects on cuttings transport and mechanical friction. The study contributes to describe the function and ability of deliberately induced non-circular geometry in wellbores as means to achieve a more efficient drilling and well construction. Improving hole cleaning will improve drilling efficiency in general, and will in particular enable longer reach for ERD wells. Reduced mechanical friction may improve the drilling process and many operations during the completion phase.

The laboratory experiments were performed in an advanced flow loop setup reproducing field-relevant flow conditions. The flow loop consists of a 10 m long 4” inner diameter borehole made of concrete. A free whirling rotational string with 2” diameter provides a realistic down hole annular geometry. A field-relevant oil based drilling fluid (OBM) was circulated through the test section at different flow rates. To represent the effect of rate of penetration, synthetic drilling cuttings (quartz sand particles) were injected at different rates through the annulus in the horizontal test section. The test results show that borehole hydraulics and cutting transport properties are significantly improved in the non-circular wellbore relative to the circular wellbore. The effect of the mechanical friction is more complex, yet significantly different for the two geometries.
Testing Marine Renewable Energy Devices in an Advanced Multi-Directional Combined Wave-Current Environment
Authors: Noble Donald R. , Draycott Samuel , Davey Thomas A. D. , Bruce Tom
Published: October 2017

Physical scale model testing is an important development tool, used extensively to study the behaviour of marine devices, vessels and structures in a controlled environment prior to deployment at sea. Whilst specific guidance on developing and testing marine renewable energy devices has been published over the past decade, it has limitations in terms of advanced environmental conditions for testing. The body of existing guidance is reviewed, and initial suggestions offered for additional test conditions that may be considered in later stages of model testing. This focuses on testing in combined waves and currents, particularly the multi-directional aspect thereof, which is now possible in facilities such as FloWave.
Wave Flume Tests to Check a Semi-Analytical Method for Calculating Solitary Wave Loads on Horizontal Cylinders
Authors: Filianoti Pasquale , Gurnari Luana , Aristodemo Francesco , Tripepi Giuseppe
Published: October 2017

In this work, the solitary wave loads on a submerged horizontal circular cylinder are studied by comparing new analytical results with ad-hoc experimental data. The proposed analytical solution has been recently proposed by Gurnari and Filianoti (2017) and represents an extension of the formulation developed by Filianoti and Piscopo (2008) to assess the solitary wave loads acting on a submerged breakwater and tested in a wave flume on a small-scale model (Filianoti and Di Risio, 2012). Here we deal with a submerged horizontal cylinder following the concept that a solitary wave is subjected to a slowdown passing over a submerged cylinder. A laboratory investigation was addressed to calibrate the adopted semi-analytical method. The speed of the solitary wave celerity crossing the solid submerged cylinder was measured for several wave amplitudes. In the adopted wave flume at the University of Calabria equipped by a piston-type wavemaker, an horizontal cylinder with diameter D = 0.127 m was posed with its center at a depth of 0.2 m. Twelve transducers measured the instantaneous pressures along the external contour of the body. A battery of wave gauges measured the free surface elevation to evaluate the celerity crossing the equivalent water cylinder. Tests confirmed the existence of the slowing down of the celerity of the wave pressure. In other words, we found that the pressure wave is nearly double the time necessary to cross the cylinder with respect to the time necessary to cover the same distance in the undisturbed field, for solitary waves amplitudes ranging from about 0.08 and 0.19 times the water depth. The slowing down increases the horizontal wave force on the solid body with respect to the Froude-Krylov one. Moreover, it appears that in the adopted experimental range the wave force is essentially inertial if compared to the drag one, enabling us to rely upon a simplified analytical model to obtain an effective estimate of the horizontal force produced by a solitary wave on a cylinder.
Study of the Influence of Shale Anisotropy Orientation on Directional Drilling Performance in Shale
Authors: Abugharara Abdelsalam N. , Hurich Charles A. , Molgaard John , Butt Stephen D.
Published: October 2017

The influence of shale anisotropy orientation on shale drilling performance has been studied using a new laboratory procedure. This procedure includes drilling and testing three sets of shale samples in different orientations from a single rock sample. Shale samples of different types were collected from outcrops located at Conception Bay South (CBS) in Newfoundland, Canada. For predrilling tests, oriented physical and mechanical measurements on each type of shale were conducted on the same rocks that will be drilled later. For drilling tests, three sets of tests were conducted. Each set was in a different orientation, corresponding to those in the physical and mechanical measurements. Each set was conducted under the same drilling parameters of pressure, flow rate (FR), and weight on bit (WOB) using a fully instrumented laboratory scale drilling rig. Two different types of drill bits were used, including a 35 mm dual cutter PDC bit and a 25.4 mm diamond coring bit. The drilling data was analyzed by constructing relationships between drilling rate of penetration (ROP) versus orientation (i.e. 0°, 45°, or 90°). The analysis also included relationships between WOB and bit cutter Depth of Cut (DOC), Revolution Per Minute (RPM), and Torque (TRQ). All the above relations were evaluated as a function of shale bedding orientation. This evaluation can assist in understanding the influence of shale anisotropy on oriented drilling. Details of the conducted tests and results are reported.
Efficient Algorithm for Discretization of Metocean Data Into Clusters of Arbitrary Size and Dimension
Authors: Kanner Samuel , Aubault Alexia , Peiffer Antoine , Yu Bingbin
Published: October 2017

In order to run a fatigue analysis on a floating structure, it is common practice among ocean engineers to rely upon a large set of test cases, each with a unique set of environmental conditions. For a specific test site, the issue remains of how to obtain a limited set of environmental conditions for these test cases, sometimes known as bins, which can accurately recreate the conditions. When considering a floating offshore wind turbine, it is necessary to obtain a timeseries of not only the wave conditions, but also the wind conditions (and perhaps current, if possible). Thus, it is common to have greater than 5 dimensions in the time-series (e.g., significant wave height, wave period, wave direction, wind speed, wind direction, etc). The creation of bins in two dimensions is quite easily solved by creating an arbitrary grid and taking the mean of all the observations which fall in a specific cell. In higher dimensions, an N-dimensional cell is not easily visualized and so the resulting set of bins cannot easily be graphically represented. In this paper, an efficient, iterative algorithm is developed to convert N-dimensional metocean data into a set of discrete bins of arbitrary size. The algorithm works by setting a tolerance level on the number of observations that must be included in a cell in order to create a bin. If the population threshold is not met, the observations remain unbinned and another iteration is required. Generally, the population threshold can be a function of iteration number so that all observations will be binned. The algorithm can properly take into account extreme data by setting a tolerance level on the N-dimensional distance by which an observation can be included in a certain bin. A quality measure, q, is created to measure the level of representation of the original data by a set of bins, independent of the number of bins. Depending on the tolerance levels, the algorithm can be completed in seconds on a normal laptop for the available data set of 20 years with a 3-hour sampling rate. The observations and bins from a case study are shown as an example of how the bins can be created and visualized.
Collapse Propagation of Deep Water Pipelines
Authors: Souza Ana Paula França de , Solano Rafael F. , Azevedo Fabio B. de , Karjadi Erwan , Ferraz Caroline
Published: October 2017

Nowadays, the global trend is an increasing need for oil and gas. As the easily recoverable fields have been already developed, the trend in the offshore oil and gas industry is going deeper into the more challenging outlook, such as outside West Africa, the Brazilian Pre-Salt developments and in the Gulf of Mexico. For ultra-deep waters the main design challenge is related to the high external pressure that may cause collapse of pipelines. This potential failure mode is normally dealt with by increasing the pipe wall thickness, but at ultra-deep waters this may require very thick pipe that becomes very costly, difficult to manufacture and hard to install due to its weight. Facing the challenges of the pipeline design for ultra-deep waters, the Collapse Joint Industry Project (JIP) was started to develop a guideline for wall thickness design optimization for offshore pipelines with external diameter to wall thickness ratio less than 20 (D/t < 20). As part of the JIP, nine buckle propagation tests were conducted on full scale seamless pipes. This paper describes these experiments and new conclusions that were raised in light of the test results.
Use of Wet Dam-Break to Study Green Water Problem
Authors: Hernández-Fontes Jassiel V. , Vitola Marcelo A. , Silva Monica C. , Esperança Paulo de Tarso T. , Sphaier Sergio H.
Published: October 2017

Green water occurs when an incoming wave exceeds the freeboard and propagates on the deck of naval/offshore structures, such as FPSO’s and platforms. The water on deck can affect the integrity of facilities and equipments installed on it, compromise the safety of the crew and affect the dynamic stability of the structure. Traditionally, regular or irregular waves generated by different types of wave-makers have been used to reproduce green water events. This is a good practice to study consecutive events. However, to study isolated events, an alternative could be the use of the wet dam-break approach to generate the incoming flow. The purpose of this paper is to investigate experimentally the use of the wet dam-break approach to generate isolated green water events. Tests were carried out in a rectangular tank with a fixed structure. Different freeboard conditions were tested for one aspect ratio of the wet dam-break (h0/h1 = 0.6). High speed cameras were used to investigate the initial phases of green water. Results demonstrated the ability of this approach to represent different types of green water events.
Effects in Free Water Knockout Separator Caused by FPSO Motions in Ocean Waves
Authors: Fernandez Martins Catharine , Morooka Celso Kazuyuki
Published: October 2017

In offshore operations, wind, waves and currents cause motions on Floating Production Storage and Offloading (FPSO) platforms that can induce effects on equipment at the topside processing plant, such as on an oilfield separator. The purpose of this work is to propose a procedure to evaluate the quality of the emulsion separated in a horizontal Free Water Knockout separator (FWKO) under the influence of the FPSO motions in ocean waves. In this paper, a software named WAMIT© was used to obtain FPSO motions. Time series of roll and pitch motions are calculated considering regular and irregular waves and through these results the emulsion quality indicator is obtained to evaluate the separator performance. The main contribution from the present study is the estimation of the quality of the emulsion separated on the FWKO, which can contribute to improve the operational criteria for three-phase separators commonly used in offshore applications.
Finite Element Analysis of Umbilical Cables Anchoring Systems
Authors: Ribeiro Malta Eduardo , Toni Fernando Geremias , Guedes Mendonça Heloísa , de Arruda Martins Clóvis , Morini Rafael Giovane , Tanaka Rafael Loureiro
Published: October 2017

The connectors on an umbilical system are critical components that are subjected to high tensile loads. To ensure tension resistance to an umbilical cable connection, its structural elements must be properly anchored to the armor pot. One way to provide that connection is the use of the adhesive properties of an epoxy resin. In that context, it is necessary to perform a series of pull out tests in order to verify if the resin is capable of withstanding the tensile loads transmitted by the tensile armor layers or the steel tubes. For that purpose, a series of tridimensional finite element models are being developed to represent, as realistic as possible, the interaction between metallic layer and resin. These models allow a fully helical tensile armor to interact with a resin substrate. For this article, an early stage model considering bonded contacts is presented and the adhesion of the tensile armor tendons is evaluated in terms of the shear stresses in the contact regions.