bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite Element Analysis of a Flexible Pipe Interlocked Carcass Under Tension Loads
Authors: Geremias Toni Fernando , Provasi Rodrigo , de Arruda Martins Clóvis
Published: October 2021

To correctly model the structural behavior of a flexible pipe, the contribution of all the layers must be completely understood, among them the interlocked carcass. That carcass is a metallic layer designed to provide radial stiffness to a flexible pipe, mainly supporting pressure differentials and thus preventing failure modes such as collapse and crushing, but its behavior under other loads is worth of investigation. This paper contributes to understanding the carcass behavior under tension. Given its complex helical and interlocked geometry, modelling the carcass through the Finite Element Method is a challenging task, not only due to the large size of the models, but also due to the nonlinearities and convergence difficulties that arise from the self-contacts at the interlocking. For these reasons, most works developed over the past decades have adopted an equivalent layer approach, in which the carcass is replaced by an orthotropic cylindrical layer with equivalent mechanical properties. Although practical, this approach disregards the effects from the interlocking, such as stiffness variations and stress concentrations. Therefore, aiming a more realistic representation and a better understanding of the mechanical behavior of the interlocked carcass, this work presents four different carcass finite element models to analyze this layer under tension loads. The first one is a complete three-dimensional finite element model of an interlocked carcass discretized with second order isoparametric solid elements and surface-to-surface contact elements. The second model consists of a version of the first one with the addition of an inner polymeric sheath. As for the third and fourth models, it was adopted the simplifying ring hypothesis, that is, a carcass with 90 degree lay angle, thus allowing the axisymmetric modelling of the two previous configurations, representing a substantial computational gain by using two-dimensional meshes. The results of those models are then presented and compared, and the validity of the adopted simplifying hypothesis is verified.
Pitting and Corrosion Rates of Coated, Uncoated, and Insulated A333 Steel Pipelines in Marine Harsh Environment
Authors: Hillier Alan , Khan Faisal , Caines Susan
Published: October 2021

Pipelines are one of the most economical and safe means of transporting useful materials, and their design life depends on protection mechanisms present. Marine environments increase corrosion rates due to moisture, and elements like chloride which increase localized pitting rates. Thirty-six A333 low temperature carbon steel pipelines were placed at Argentia, NL, an extremely corrosive environment (C5) near high tide mark. The experiment consisted of coated, uncoated, and insulated pipes. Exposed for a period of two years, corrosion rate, optical inspections, and pit depth were recorded at intervals. The highest average pit and maximum pit depth occurred in uncoated insulated pipes and coated uninsulated pipes. The highest average mass loss occurred in uncoated (insulated and uninsulated) pipes. The least mass loss and pit depths generally occurred in coated pipes (both insulated and uninsulated). Corrosion near the ends of the pipes were more significant than other locations. Final averaged corrosion rates for insulated coated and uncoated pipes, were 0.017 and 0.021mm/yr respectively. Corrosion rates for uninsulated coated and uncoated pipes, were 0.014mm/yr and 0.023mm/yr respectively. Maximum and mean pit depths for insulated coated and uncoated pipes were, 180/156 and 256/205 microns, respectively, while for uninsulated coated and uncoated were 210/177 and 182/148 microns, respectively. Some coated and uncoated insulated pipes had negligible pitting and corrosion. Results provide an increased understanding of corrosion rates, corrosion under insulation corrosion, and under coating, and pitting data for pipelines in service in marine harsh environments.
Plug and Abandonment Trends in Albertan Gas Wells
Authors: Trudel Elizabeth , Bizhani Majid , Frigaard Ian
Published: October 2021

Alberta is known to be a significant oil & gas producer with over 468,000 wells drilled in the province since the beginning of the twentieth century. While the majority of these wells were drilled to produce oil, approximately 165,000 gas wells can be found in Alberta and are studied here. This represents a more than six-fold increase over Alberta’s western neighbor, British Columbia, which is known to be a primarily gas producing province. Over 80% of the gas wells in Alberta have yet to enter the abandonment stage. A growing stock of suspended wells can be found in the province which comes with an increase in liability for all parties involved i.e., the operators, the provincial regulator and the Orphan Well Association (OWA). Here we analyze abandonment trends in Alberta, showing that combining the growing suspended well stock with the shorter lifetime associated with the horizontal gas wells currently being drilled in the province, we can expect a wave of well abandonments in the coming decades. We focus only on gas wells, where we can make a comparison with a similar study previously conducted for wells in British Columbia.
Effect of Marine Nuclear Reactor Environment to Ship’s Structural Responses
Authors: Jeong Han Koo , Kim Soo Hyoung
Published: October 2021

As the regulations on greenhouse gas emissions at sea become strict, technology development to minimize environmental pollutants emitted from the propulsion system of ships is actively underway. Research on the use of renewable energy as a power source of ships propulsion system pursuing eco-friendliness is continuously carried out. However, considering the recent development of ships’ large-scale, and at the same time minimizing greenhouse gas emissions at sea, the interest in nuclear energy as the means of a stable supply of environmentally friendly large-capacity energy has been increased. In this study, the effect of marine reactor operation on the material properties of a ship hull material is reviewed, and from this, hull structural behaviors are investigated. Attention is paid to the neutron irradiation on the material in the reactor operation environment, and then the strength assessment of a hull structural member assumed in the neutron irradiation situation is performed. Considering the neutron irradiation effects, the Young’s modulus, poisson’s ratio and allowable stress of DH36, typical high tensile strength steel used in ship hull, are varied based on the research findings related with the topic of neutron irradiated steels. Rectangular stiffened plated structures, basic common structural members for ship hull, are exemplified for the strength assessment to understand their structural behaviors such as strength and stiffness. Results from this study provide information on the effect of neutron irradiation on the hull structural behaviors of the ship using nuclear power and possibly can supplement the hull structure part from classification societies’ rules and regulations.
PyraWind™: An Innovative Floating Offshore Wind Turbine (FOWT) Global Performance Analysis
Authors: Yang Zhiyong , Bian Xiaoqiang , Shi Yu
Published: October 2021

In the near future, the offshore wind industry will experience a significant increase of turbine size and of floating wind development activities. A floating offshore wind turbine foundation offers many advantages, such as flexibility in site selection, access to better offshore wind resources, and quayside integration to avoid a costly heavy lift vessel offshore campaign. PyraWind™ is a patented three canted column semisubmersible floating foundation for ultra large offshore wind turbines. It is designed to accommodate a wind turbine, 14 MW or larger, in the center of the interconnected columns of the hull with minimal modifications to the tower, nacelle and turbine. The pyramid-shaped hull provides a stable, solid foundation for the large wind turbine under development. This paper summarizes the feasibility study conducted for the PyraWind™ concept. The design basis for wind turbine floating foundations is described and the regulatory requirements are discussed. Also included are the hydrodynamic analysis of the hull and ongoing work consisting of coupling hull hydrodynamics with wind-turbine aerodynamic loads. The fully coupled system was analyzed using OpenFAST, an aerodynamic software package for wind turbine analysis with the ability to be coupled with the hydrodynamic model. Due to the canted columns, a nonlinear analysis was performed using the coupled numerical hydrodynamic model of the platform with mooring system in extreme sea states.
Validation of a Simplified Transient Multiphase Flow Model for Any Pipe Inclination With Gulf of Mexico Field Data
Authors: Tornisiello Ligia , Xavier Teles Francisco Bruno , Waltrich Paulo J.
Published: October 2021

This paper presents a simplified model for transient two-phase flow in pipes of any inclinations, for slow transients. Such simplified model facilitates its use for real-time monitoring and machine leaning implementations.

An improved correlation for the drift flux parameters is adopted in the model, which enables the utilization of the model for simulating transient flow scenarios for any pipe inclination and extends its applicability to a wider range of conditions. From the formulation, an equation has also been proposed to quantitatively define the application of the concept of slow transient. This equation indicates if a case of interest can be classified as a slow transient, which consequently implies that the use of the proposed model would likely provide accurate results.

The model has been validated with experimental and field data, and also compared to the state-of-the-art commercial simulator for transient two-phase flow in pipes. The results showed an agreement within the range of ±30% for the holdup predictions for 65% of the scenarios, and an agreement within the range of ±30% for the pressure predictions for 82% of the scenarios considered in the validation data set. The model performance evaluation with data from a well in the GOM showed a maximum error of 30% in terms of predicted bottomhole pressure and an average error of 9% for the simulation of two years of transient flows.
A Prediction Model of Wellbore Temperature Based on Hydration Kinetics During Well Cementing in Nature Gas Hydrates
Authors: Xue Yucheng , Lu Haoxin , Wang Chengwen
Published: October 2021

Stability of nature gas hydrates (NGH) is greatly impacted by temperature. Because intense heat is released from cement hydration during well cementing, limiting the temperature rise of cement is critical for safe cementing of NGH well. The total heat release by cement slurry has a strong correlation with the mechanical properties of cement slurry. Consequently, reducing the heat of hydration of cement means typically results in lower strength of the cement stone. Traditional evaluation methods do not fully consider the complex interaction between cement hydration reaction and heat transfer in the wellbore, therefore, it is difficult to determine whether the cement slurry formula selected is suitable for well cementing in nature gas hydrates. In this paper, a model to predict cement wellbore temperature was developed by incorporating the complicated interactions between temperature and cement hydration reaction. The model established the relationship between degree of cement hydration and wellbore temperature based on the cement hydration reaction kinetics. Coupled with differential method and numerical calculation, the influence of wellbore temperature on NGH was analyzed during the cementing process. The newly developed model was used to predict the field performance. Model predicted data and field data are within 10.0%. By accurately predicting the change of NGH with wellbore temperature during the cementing process, the model in this paper can not only effectively guide the research and development of low hydration heat cement slurry for NGH well but also find and avoid safety hazards in time during the design process of NGH cementing slurry.
Strength Prediction of Connector Structure of the Double-Module Semi-Submersible Platform
Authors: Minggang Tang , Ziyuan Wang , Chun Xu , Shengpeng Li , Yuchao Chen , Xinyun Ni
Published: October 2021

A double-module semi-submersible platform for scientific experiment has been applied firstly in practical engineering. Hinge-type connectors are used to link the two modules reliably and release the relative pitch freedom, and the strength of connector structures determines directly the integrity and safety of the platform. In this paper, the three-dimensional finite element model of the platform structure is developed including the local features of connectors, and main elastic modes are obtained. By using the Potential flow theory and the Green Function method, the hydrodynamic coefficients of the model are determined. Based on the three-dimensional hydroelastic theory, the response amplitude operators (RAOs) of generalized coordinates associated with different order modes are investigated. That indicates the structural deformation of connectors is excited mainly by modes of horizontal bending moment and torsion, and the stress responses in the longitudinal bulkheads close to bearings are generally marked. Using the modal superposition method, the RAOs of stress in the typical joints of connector structures are calculated under the given wave directions. Considering the JONSWAP spectrum and the amplitudes of stress responses of connector structures following Rayleigh distribution in short term, the strength of the connector structure is predicted in short term. In order to verify the correctness of the strength prediction method presented in this paper, more than thirty stress sensors are installed on the typical joints of connector structures of the double-module semi-submersible platform located in the real sea. Those stress responses are monitored during the typical typhoon activity, and the statistical data is compared with the predicted results from the theoretical model. Both the distribution trend and magnitudes of the results from the two methods are principally consistent that validates the given model. This theoretical method may provide an effective tool to analyze the strength of connector structures of multiple-module offshore platform.
Optimization and Evaluation of Chemical Shrinking Agent for Deposits in Salt Cavern Gas Storage
Authors: Ran Lina , Liu Shuang , Wanyan Qiqi , Yao Erdong , Bai Song
Published: October 2021

Salt cavern gas storage is an important strategic method to shave the fluctuation of supply-demand of natural gas in China. However, due to low grades of salt beds, there remains lots of insoluble sediments accounting for 1/3 up to 2/3 of the storage capacity at the bottom of cavity. The use of chemical agent with the function of swelled-clay-shrinking is an effective method for enlarging actual cavity volume. Clay swelling and physical deposits experiments were conducted to select the suitable chemical shrinking agent and study the relation between salt rock and agent. A device simulating the leaching process of insoluble sediments was developed to evaluate different factors on residue deposits and XRD (X-Ray Diffraction) was used to analyze mineral compositions of various salt caverns. The results showed that the main controlling factor for the volume swelling of the bottom insoluble sediments in the salt cavity is the electrostatic repulsion. These hydrated cuttings carry a negative charge leading to the electrostatic repulsion between each other, which promotes the loose accumulations of these physical deposits. The relation between rock and shrinking agent is clarified and the selected chemical agent has an excellent adaptation in salt cavern gas storages through the tests above. In addition, the result provides an experimental basis for minimizing the volume of the salt carven sediments to store more natural gas.
A Comparison of Inverse Models for the Estimation of Ice-Induced Propeller Moments on a Polar Vessel
Authors: Nickerson Brendon M. , Bekker Anriëtte
Published: October 2021

Full-scale measurements were conducted on the port side propulsion shaft the S.A. Agulhas II during the 2019 SCALE Spring Cruise. The measurements included the shaft torque captured at two separate measurement locations, and the shaft rotational speed at one measurement location. The ice-induced propeller moments are estimated from the full-scale shaft responses using two inverse models. The first is a published discrete lumped mass model that relies on regularization due to the inverse problem being ill-posed. This model is only able to make use of the propulsion shaft torque as inputs. The second model is new and employs modal superposition to represent the propulsion shaft as a combination of continuous modes, resulting in a well-posed problem. This new model requires the additional measurement of the shaft rotational speed for the inverse solution. The continuous model is shown to be more consistent and efficient, which allows its use in real-time monitoring of propeller moments.
Reconstructing Sea-States in the Southern Ocean Using Ship Motion Data
Authors: Nelli Filippo , Van Zuydam Armand , Pferdekamper Karl , Alberello Alberto , Derkani Marzieh , Bekker Anriëtte , Toffoli Alessandro
Published: October 2021

Sea state conditions can be estimated from the motion of a moving ship by converting its response to incident waves through the response amplitude operator. The method is applied herein to ship motion data from the icebreaker R/V Akademik Tryoshnikov and recorded during the Antarctic Circumnavigation Expedition across the Southern Ocean during the Austral summer 2016–17. The response amplitude operator of the vessel was estimated using two boundary element method models, namely NEMOH and HydroSTAR. An inter-comparison of model performance is discussed. The accuracy of the reconstructed sea states is assessed against concurrent measurements of the wave energy spectrum, which were acquired during the expedition with the marine radar WaMoS-II. Results show good agreement between reconstructed sea states (wave spectrum as well as integrated parameters) and direct observations. Model performances are consistent. Nevertheless, NEMOH produces slightly more accurate wave parameters when quantitatively compared against HydroSTAR.
Flow Characteristics of Foam in Fractures and Prediction of Preferred Paths
Authors: Xu Zhengxiao , Li Zhaomin , Li Binfei , Chen Danqi , Zeng Xianghui , Wei Yao , Ji Changfang
Published: October 2021

Foam is widely used in fractured reservoirs. The flow characteristics in complex fracture networks are still unclear, and there are few numerical simulations of foam fluid flow in fractures. In this study, a variety of combined visual fracture models were used to observe the flow characteristics of foam in the fracture. Firstly, based on the parallel fracture model, the foam flow characteristics under different fracture depths were explored, and then based on the complex fracture network model, the foam flow path and sweep efficiency are evaluated. Finally, the Dijkstra’s algorithm was used to determine the weighted graph of the fracture network nodes, and the preferred flow paths of the foam were predicted. The results show that when foam flows in parallel fractures with different depths, it preferentially flows in high permeability (100 μm) fractures, and there is gas trapping in low permeability (50 μm) fractures. In the irregular fracture network model, the sweep efficiency of the foam fluid is greatly affected by the foam quality, and the sweep volume is the widest when the foam quality is about 90%. The simulation results based on the Dijkstra’s algorithm can be fitted to the experimental results to a certain extent. By controlling the number of preferred paths and the weight of nodes, the plugging and regulating performance of the foam are characterized. These findings reflect the necessity of considering fractures when foam flows in reservoirs, and provide a certain experimental basis and theoretical guidance for the development of fractured reservoirs.
Determination of Hydrodynamic Masses and Roll Periods of Ships in Shallow Water
Authors: Jannsen Larissa , Krüger Stefan
Published: October 2021

Due to the fast increase of the vessels’ size over the past few years the actual water depth is becoming more and more relevant for seakeeping problems. The highly frequented sea route TSS Terschelling – German Bight for example is a shallow water route for large vessels which are now affected by the reduced keel clearance. Many shallow water depth areas occur also in coastal areas or inland seas. If a vessel is travelling in shallow water sea states, the hydrodynamic forces will change compared to deep water sea states and they are essential for further seaway calculations. Furthermore, a rough but easy evaluation of the incoming seaway is the roll period. Shallow water effects should be taken into account for calculating roll periods and thereby predicting a manageable or risky seaway situation. This paper presents the implementation of shallow water effects into an existing 2D panel code. With this panel code the hydrodynamic forces for the vessel’s frames are calculated based on the potential theory in the frequency domain, which is a validated approach in the early design stage. The panel code is part of the ship design environment E4 which is being developed by the Institute of Ship Design and Ship Safety, among others. With the expanded method it is possible to calculate hydrodynamic forces also in shallow water in all degrees of freedom. Therefore, the frame motions are converted to global ship motions. Furthermore, for the usage in the early design stage the calculations should be fast but also accurate. The obtained calculation results are therefore validated with full scale measurement using Inertial-Measurement-Units.
Development and Testing of Bridle Line Power Generation for Aquaculture
Authors: Grehan Patrick , Casey Conor , McEvoy Paul , Wann Annicka
Published: October 2021

This paper presents the development and testing of Gator, a hydraulic Power Take Off (PTO) being commercialised for the Aquaculture market. Gator uses a novel polymer bellows to pump pressurised water through a power take off system, while also providing a non-linear force response that reduces mooring line loads over traditional mooring lines.

The Gator system is comprised of 4 distinct subsystems: The Gator pump, hydraulics, turbine, and electrical storage & control. The Gator pump is a polymer component that compresses under load, pumping water through check valves into the hydraulic system. The connected hydraulic system takes the pressurised water, regulates the pressure and flow rates with an accumulator, and provides a steady flow of water to the turbine, generating electricity.

This paper will provide an overview of the technical development of the Gator system over several phases, which has focussed its adaptation for use in the aquaculture industry as an inline pump on cage mooring lines.

A description of comprehensive testing undertaken on a linear test rig to simulate the variable loading that the system would experience in operation will be provided as well as some of the early characterisation results from this testing.
Digital Twin of a Maneuvering Ship: Real-Time Estimation of Derivatives and Resistance Coefficient Based on Motion Sensor
Authors: Uehara Sasaki Humberto A. , Ianagui André S. Sandes , Cardozo de Mello Pedro , Tannuri Eduardo Aoun
Published: October 2021

Retrieving certain hydrodynamics coefficients from a marine craft during a maneuver can be useful for various reasons, such as the validation of project specifications or the rapid verification of structural changes that could impact the vessel movement. Intended to estimate some of these parameters, the present work proposes a method purely based on traditional Extended Kalman Filter (EKF) focused for limited drift angles.

Albeit not posing as a replacement to conventional estimations, such as from Computer Fluid Dynamics (CFD) — which solve equations in order of millions — and experimental tests — with its time-consuming preparation setups and post-analyses — the method can possibly present itself as a convenient and quicky technique to estimate the hydrodynamics coefficients in real time, as each iteration resorts only into a few dozen of equations.

Preliminary results in the simulated environment called pyDyna — a python version of the Numerical Offshore Tank ship maneuvering simulator — indicate this procedure is faster along with an acceptable margin of accuracy, possibly pointing as a feature for future digital twin applications.
Translational Periodic CFD Model: A Practical Solution to Capture Hydrodynamic Slugging in Horizontal Pipes
Authors: Agrawal Madhusuden , Khanna Samir , Kopliku Ardjan , Lockett Timothy
Published: October 2021

Prediction of erosion rate, flow-induced vibrations and fatigue assessment depends strongly on the way multiphase flow occurs through fittings such as bends, tees, manifolds, etc. Therefore, it is important to have a better understanding of multiphase flow behavior to improve confidence on erosion and fatigue prediction. Though multiphase modelling is technically possible, it cannot be confidently deployed for field scale problems due to lack of validation and excessive requirement for computational resources. When simulating multiphase flow through a long horizontal pipe, it is important to specify appropriate boundary conditions for the gas and liquid phases at the inlet which can correctly define the slug length and velocity. This paper presents a translational periodic Computational Fluid Dynamics (CFD) model which can effectively capture slug flow in horizontal pipes as the slug unit cell can be approximated as periodic in the axial direction. The simulation of the slug flow was performed in a pipe section, with periodic boundary conditions under imposed pressure gradient and fixed overall liquid hold-up. Starting from smooth stratified flow, the slug flow pattern is simulated and validated in terms of slug speed and superficial velocities for gas and liquid phases.

Furthermore, sensitivity studies were performed to understand the effect of mesh resolution, turbulence model, multiphase model, and time step size on CFD predictions in translationally periodic horizontal straight pipes. Experimental datasets of Manolis (1995) on high pressure gasliquid slug flow for hydrodynamic slugging in a horizontal pipe were used to validate multiphase CFD modelling. Subsequently an efficient algorithm was developed to couple results from periodic domain model of straight pipe to a more complex pipe configuration with one (or more) 90° bends. This algorithm was successfully demonstrated on TNO FIV JIP dataset (Belfroid et Al., 2016) for prediction of multiphase flow behavior and fluid forces in horizontal pipe with bend.
A Hindcast Model for Evaluation of Iceberg Management Operations
Authors: Fuglem Mark , Stuckey Paul , Turnbull Ian , Thijssen Jan , Huang Yujian
Published: October 2021

When planning oil and gas exploration and production operations off the east coast of Canada, the potential for iceberg impacts must be considered. Environmental conditions in this region can be very harsh, and iceberg trajectories are notably unpredictable. When an iceberg has the potential to impact a Floating Production, Storage, and Offloading (FPSO) platform, ice management through towing will be attempted; and if this fails, the production system will be shut down, line flushed, the mooring and riser systems disconnected, and the platform moved off site.

If trajectory forecasting were highly accurate, only icebergs passing very close to the platform would require ice management and possible shutdown of the platform. Given natural variations in wind, currents, and waves, and challenges measuring and forecasting these parameters, there is considerable forecast uncertainty. This results in added expenses for extra ice management and unnecessary shutdowns.

Improvements in trajectory forecasting accuracy, characterization of forecast uncertainty, and methods to account for these uncertainties in operations would all be beneficial. This paper outlines an approach for simulating large numbers of iceberg trajectories in varied and realistic environmental conditions from hindcast met-ocean data in conjunction with a forecasting uncertainty model derived from forecast validation studies. A model, named BergCast, was developed so that proposed strategies for improving ice management operations can be evaluated, and the value of reducing forecasting uncertainty quantified.
Development of Iceberg Profiling Technology
Authors: Bruce Jonathon , Yulmetov Renat , King Tony , Ralph Freeman , Younan Adel
Published: October 2021

Iceberg management on the Grand Banks of Newfoundland, Canada is currently carried out without knowledge of the underwater shape of the iceberg. An iceberg profiling system is being developed to integrate the rapid generation of 3D iceberg shape data with a collection of tools that utilize the data to provide recommendations, intended to improve iceberg management effectiveness. The intent is for the system to be operated by vessel crew with minimal training.

The system utilizes a LiDAR and a pole mounted multibeam sonar to profile the iceberg sail and keel, respectively. A vessel equipped with the profiling system circles an iceberg twice to collect a profile, a process that on average requires approximately 15–30 minutes. The data is collected in the form of a point cloud, which must be de-noised and corrected for both drift and rotation of the iceberg. Tools have been developed to assess the stability of the iceberg, and to consider the shape of the iceberg relative to towing net dimensions, to provide guidance to the operator regarding the recommended towing direction to avoid iceberg rolling or net slippage events. Other applications of the profile data include an impact loads analysis tool that determines the distribution of potential iceberg loads in the event of a collision with a given platform, and an operational iceberg drift model that uses the iceberg shape to improve iceberg drift forecasts.

Large-scale field programs were carried out in both 2018 and 2019 as part of the development process for the system. Data collected has shown that iceberg characteristics have changed significantly when compared to iceberg profile data collected in the 1980s. For a given iceberg waterline length, the more recent data shows significantly reduced drafts. The 1980s iceberg dataset currently dominates the data used as the basis for assessing iceberg loads on surface facilities and iceberg risk to subsea assets. Reduced iceberg drafts will result in reduced risk to subsea facilities and pipelines.

These results and observations demonstrate the usefulness of the iceberg profiling system as an environmental monitoring tool, and the data collected has design and operational applications. The development and capabilities of the system are presented, as well as the comparison of the 1980’s and newer iceberg datasets and implications for iceberg risk to facilities on the Grand Banks and surrounding regions.
The Evolved Motions of a Marine Riser or Pipeline
Authors: Zueck Robert F.
Published: October 2021

Analytical, experimental and computational models have historically been heavily simplified, linearized, and otherwise reduced. This paper shows how such model reductions eliminate the fundamental geometric changes that determine real behavior in cables, strings, moorings, guys, pipelines, riser, plates, skins, subsea hulls, and other such slender and thin structures. The paper details each physical quantity that we must add back into our overly reduced models to improve the basic nature, evolution, and accuracy of the resulting motions and vibrations.

For example, even slight changes in local rotation anywhere along a cable can create large nonlinear changes in the dynamic nature of its behavior. The evolved complexity of the resulting global motions and vibrations in space and time often defy what we normally expect from such a simple structure.

Although this paper focuses on the modeling of deep-water moorings and risers of an ocean platform, the same geometric effect is fundamental to most science and engineering models. Understanding how small changes in geometry can nonlinearly affect any structured behavior will help demystify much of the poorly-understood motions and vibrations in a large diversity of applications, including induced vibrations, sound, structural acoustics, aero-elasticity, sound, light and atomic radiation.
FPSO Mooring Line Integrity Supervising System Based on Motion Data and Natural Frequency Estimation
Authors: Costa José Lucas De Melo , Queiroz Filho Asdrubal N. , Santos Ismael H. F. , Barreira Rodrigo Augusto , Costa Anna Helena Reali , Gomi Edson Satoshi , Tannuri Eduardo Aoun
Published: October 2021

Offshore production facilities play a central role in the oil industry given the growing demand for energy resources. The mooring system of these floating structures is a critical component for safety maintenance. The timely identification of mooring lines failures can prevent environmental pollution, property losses and further system failures. In this paper we propose a system to detect and classify failures of the mooring lines based on the natural period in the longitudinal axis and in the lateral axis of the long drift oscillatory motion of the platform. The proposal starts from the hypothesis that when a line break occurs, the natural period of oscillation of the platform is increased, and this difference may indicate the malfunction of the mooring system. The proof of concept developed for the proposed system demonstrates the potential of using the natural period to detect failures in mooring lines for floating vessels, validating the initial hypothesis that the difference in a natural period appears when a line breaks and that this difference may detect line break.
Fatigue Life Extension Procedure for Subsea Wells Based on Pressure Testing
Authors: Fjeldstad Arne , Hørte Torfinn , Sigurdsson Gudfinnur , Wormsen Anders , Berg Espen , Macdonald Kenneth Alasdair , Reinås Lorents
Published: October 2021

This article presents a fatigue life extension procedure for subsea wells based on fracture mechanics. It makes use of the outcome of an internal pressure test to determine a safe period for drilling and completion. The pressure test is used as a load test and can only reveal deep fatigue cracks. The safe operational period is estimated as the number of cycles required to grow a fatigue crack from the largest fatigue crack that remains stable after the pressure test until it becomes unstable due to an accidental load. The procedure takes into account the probability of the presence of the fatigue crack that can be revealed by the pressure test. This is used to determine design fatigue factors for the procedure. The design fatigue factor is formulated in terms of the (S-N based) accumulated fatigue damage for historical operations. The procedure is illustrated with two case examples (fatigue hot spots) for illustrating the procedure in more detail: wellhead extension girth weld and wellhead profile. Conditions for use are given at the end of the article.
Flow of Yield Power Law Fluids in Horizontal Pipes-Flow Field Characterization Using Particle Image Velocimetry Technique
Authors: Sun Yanxin (Sussi) , Abou-Kassem Abdulla , Bizhani Majid , Kuru Ergun
Published: October 2021

Yield Power Law (YPL) rheological model is commonly used to describe the pipe and annular flow of drilling fluids. However, the hydrodynamic behaviour of fluids with yield stress are difficult to predict because they exhibit an inherent plug (solid like) region where the velocity gradient is zero. Moreover, it is not easy to identify the transition between this solid like and liquid regions.

Theoretical studies have been conducted in the past to describe YPL fluid flow in pipes and annuli. As a result, several models have been proposed for determining flow field characteristics (e.g. velocity profile, plug width, etc.) and frictional pressure losses. However, most of these models have been validated by limited experimental and/or field data. Similar future modeling studies may benefit from more data collected under controlled experimental conditions. Therefore, we have conducted an experimental study to investigate the hydrodynamic behaviour of yield stress fluids under laminar pipe flow conditions and the results are presented in this paper.

Water-based Yield Power Law fluids were prepared by using Carbopol® 940, a synthetic high-molecular-weight polyacrylic acid-based cross-linked polymer. Fluids with yield stresses varying from 0.75 Pa (1.56 lb/100 ft2) to 4.37 Pa (9.13 lb/100 ft2) were obtained by using Carbopol concentrations changing from 0.060% w/w to 0.073% w/w. A 9m long horizontal pipeline with, 95 mm diameter (ID) was used for the experiments. Reynolds number range varying from 97 to 1268 confirmed that all flow field characteristics measurements of YPL fluids were conducted under laminar flow regimes.

Experimental study provided detailed information about pipe flow characteristics of yield stress fluids, including full annular velocity profile, near wall velocity profile, wall slip velocity and the plug region thickness.

The study was concluded by comparing experimental results (i.e. full velocity profile, frictional pressure loss, and plug width) to predictions of models presented in the literature.

Practical implications of the results have also been discussed by considering the hydraulic design of some practical field operations such as hole cleaning.
Susceptibility to Preferential Corrosion of Pipeline Welded Joints in Condensed and Dragged Water Droplet - Part 1
Authors: Zumpano Petrônio , Cardoso Juliana L. , Panossian Zehbour , Baptista Ilson P. , Miranda Helio , Franco Marilia F.
Published: October 2021

Preferential weld corrosion (PWC) is due to the formation of galvanic cells between the weld metal (WM), the parent metal (PM) and the heat affected zone (HAZ). This work has studied PWC susceptibility in longitudinal and circumferential welded joints of submarine systems and the applicability of corrosion inhibitors to mitigate the corrosive process. DNVGL SAW 450, DNVGL SMLS 450 and low alloy forged, with different nickel, copper and silicon content were tested. Several factors influence PWC susceptibility in welded structures and those selected to be studied were weld joint geometry, PM fabrication process, welding process and welding consumable chemical content. For each welding processes, welded coupons were made with similar heat input. Pipe SAW seam welds of two different plate suppliers and different nickel and copper content were tested. Tests in circumferential weld joints were predicted for 79 different combination of chemical composition: PM chemical composition and manufacturing process; welding processes; chemical composition of welding consumables. Selected welding processes are the most used by offshore industry (SAW, mechanized GMAW and manual GTAW). The root configuration of respective welding procedure specifications produce a desired variation in width geometry. The corrosion tests started with the longitudinal joints and will be further reproduced for circumferential joints. A test procedure has been developed for corrosion evaluation through immersion test, galvanic current measurement (GCM) through zero resistance ammeter (ZRA) and localized electrochemical test through SVET. Two test solutions were considered, simulating condensed and dragged water droplets in order to verify the susceptibility or occurrence of the preferential welding corrosion in the welded joints. The results for longitudinal joints indicated a greater susceptibility to PWC in dragged water than in condensed water droplets and a greater susceptibility of joints with greater anodic potential due to a higher nickel and copper content in the parent metal. A correlation between the corrosion rates obtained in both medium and the moisture contents of gas pipelines will be performed to determine the need for the addition of corrosion inhibitors and to establish the minimum required dosage. A future work will involve circumferential joints and the evaluation of the optimal dosage of corrosion inhibitors.
Investigation on Fatigue Life Prediction of Riveted Cantilever Beam Using FEA Approach
Authors: Siva Sankara Rao Yemineni , Mallikarjuna Rao Kutchibotla , Subba Rao V. V.
Published: October 2021

Different structural elements of automobiles, ships, aircraft wings and fuselages, turbines, nuclear reactors, and other machine components are susceptible to variable loading condition. Due to this type of loading situation all the mentioned structures are undergone to the formation of internal cracks, these cracks will be grown and eventually lead to the failure of the structures. Hence, the fatigue phenomenon due to variable loading conditions is a major threat and has come into address with the technological development that happening is now a days. To avoid the failure of structures due to fatigue loading condition structures are provided with different fasteners like rivets, bolts, tack welds, etc. In this study, the structures analyzed are cantilever beams, the fasteners considered are rivets, the loading considered for analysis is fully reversed cyclic loading, and the analysis considered is the fatigue analysis, the mode of analysis is a simulation using FEA software named ANSYS R19.2 WORKBENCH software. The variable parameters considered are rivet diameter, load, and coefficient of friction at the common interface of riveted specimens. Here in this analysis, the beam dimensions are kept constant. Besides, in this study, the comparison of fatigue life for solid and riveted cantilever beams of identical dimensions is presented. The material considered for the rivets and beams is aluminum alloy.
Engineering Critical Assessment of Triple-Point Flaws in Mechanically Lined Pipes
Authors: Pépin Aurélien , Tkaczyk Tomasz , Abderrazak Riadh
Published: October 2021

There is increasing demand for subsea transport of well-produced fluids through corrosion resistant pipelines such as stainless steel or bimetallic pipes. The latter are made of carbon steel (CS) pipe and a thin (typically 3.0 mm thick) internal layer of corrosion resistant alloy (CRA) such as 316L, 625, 825 or 904L. The CRA and CS layers are adhered either metallurgically or mechanically by a means of an interference fit. Although less mature than other products, mechanically lined pipes (MLP) are more readily available and economical than both stainless steel or hot-roll bonded (HRB) metallurgically clad pipes. One of the gaps that remains to be filled relates to a reliable assessment method for confirming the MLP integrity during offshore installation and subsea service.

The CRA liner in MLP is metallurgically bonded to CS at pipe ends by overlay welding, typically deposited using alloy 625 consumable. At the triple-point interface between the liner, overlay and host pipe, cracks may initiate from fabrication flaws and grow during installation or in service. Therefore, the engineering critical assessment (ECA) should be carried out to evaluate the risk of triple-point cracks breaching the CRA layer at any stage of the pipeline’s life cycle. Currently, no recognised ECA approach exists to allow completing such an assessment.

Therefore, a bespoke integrity assessment procedure has been developed and validated both numerically and via laboratory testing. This paper outlines the ECA procedure for triple-point flaws in subsea MLP pipelines, which is undertaken through a combined analytical and numerical calculation and small-scale fracture testing. Fatigue crack growth due to cyclic loading is estimated using a geometry-specific stress intensity factor (SIF) solution derived by finite-element analysis (FEA). Ductile tearing during fracture load events is quantified by small-scale fracture testing on specimens with a representative geometry, designed to match the crack tip constraint of triple-point cracks in MLP.
Assessment of Numerical Modeling Tools for the Prediction of Ship Performance in Ice
Authors: Lau Michael
Published: October 2021

This paper provides a general review of available models used in the NRC-OCRE (National Research Council – Ocean, Coastal and River Engineering) that could be used to support the assessment of a ship’s performance in ice conditions. The models were separated into three main categories: empirical, numerical and real-time, and reviewed in terms of key strengths and weaknesses. A general overview of the modelling categories and specific models within each category is given. Within each modelling category, specific models were compared to outline the key features of both the independent models and the modelling category itself. A representative model within each category and sub-category was selected and used to present the output for a given scenario. This enabled a demonstration of output capabilities for each modelling category. It also provides the reader with additional information pertaining to the input requirements and validation for the selected models. A discussion of the integration of an ice loading model into an existing ship simulation framework is included. A specific case was reviewed in which a successful integration had occurred and was documented. This allowed for demonstration of a process that could be followed for updating one’s numerical modelling capabilities. Based on this review, guidance was provided in terms of selecting a numerical tool to extend current ship performance modelling capabilities to consider ice operations. Each modelling category and sub-category has a unique set of advantages and disadvantages. These should be considered in detail to ensure that the numerical model(s) selected are optimal in terms of their ability to assess desired scenarios and interface with existing software.
Design and Research of Offshore Oil Spill Removal Ship With Variable Angle of Attack
Authors: Ou Qibin , Yang Jin , Zhang Zhenxiang , Liu Luo , Zhang Yichi , Qu Ximo
Published: October 2021

With the continuous development of the global economy and industry, and gradually expand the size of offshore oil exploration and transportation, the possibility of oil field leakage, damage of offshore tanker, oil leakage of the offshore ship and the oil spill is increasing continuously, and the harmfulness is increasing continuously. It has seriously polluted the Marine environment and destroyed the ecological balance, and seriously wasted the oil resources. Therefore, this paper developed a kind of offshore oil spill removal ship which can quickly, accurately, and effectively recover oil spill. This paper designs an offshore oil removal device with a variable Angle of attack. Through the use of Rhino and SolidWorks modeling software for the three-dimensional overall design. The variable Angle of attack offshore oil spill removal ship can be divided into seven major systems, which are the main hull of the variable angle of attack, the side hull, the oil suction, and deoiling rollers, the oil collecting groove and oil collecting chamber, the oil baffle, the steering platform, the communication equipment, the propulsion equipment, the main hull, and the external ship docking equipment. At the same time, the new type of offshore oil absorption material is installed on the double roller oil absorption mechanism, and each component system of the offshore oil removal ship is assembled. In this paper, the design of a variable Angle of attack offshore oil spill removal ship can provide a reference for the research and design of a new offshore oil spill treatment device.