bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tie-in of a Rigid Pipeline to a Flexible Rise: Design and Installation — Challenges and Lessons Learnt
Authors: Curti Gianbattista , Lirola Francois , Pirinu Gianluigi , Pavone Diego , Perrin Frederic 
Published: November 2019

Abstract
This paper presents the experience made with the engineering and execution of the tie-in of flexible risers to rigid pipelines on a project recently completed in West Africa.
Five production and injection pipelines (10” and 6”) were tied back to the host platform with flexible risers, in Lazy wave configurations, in ∼600m water depth.
The risers are directly connected to the terminations structures (PLETs) of the rigid pipelines, through horizontal connection systems.
The structures forming the tie-in (risers, PLETs and pipelines) have been designed to accommodate axial displacements of the pipelines in the range 0.3m to 1.0m, as positive displacements (expansions) and −0.1m to −0.7m as negative displacements (contractions) of the pipelines, respectively towards and away from the risers, due to pipelines thermal expansions and pipe walking.
Note that along some of the lines anchoring structures have been installed to control pipe walking.
The tie-in interface loads were to be limited, in order not to threaten the flexible pipe, the PLETs and the connectors, and, despite the small pipeline end displacements, keeping the interface loads within allowable values, was a challenge.
The positive displacements were causing interface loads as high as 80% of the allowable values, while the negative displacements were causing up to 90% utilization of the capacity of the connectors and 95% of the allowable loading of the foundations of the PLETs.
The main drivers of such high loadings are the stiffness of the flexible pipe, combined with the layout of the tie-in.
Extensive in place analyses were done to simulate the effects of progressive displacements of the pipelines, the pipe-soil interactions and the specifics of the behaviour of the flexible pipes (hysteretic stiffness).
Full 3D FE analyses of the foundations (mud mats) of the PLETs were done, to circumvent the limitations of a classical bearing capacity analysis approach.
As built information were also used, to remove some conservatisms in the assumptions initially taken in the design. A special installation procedure was implemented, to achieve a layout of the riser at the approach of the pipeline capable to better relieve the displacements of the pipelines and reduce interface loads.
Feedbacks from the installation are given in the paper.
The lessons learned are also presented: a “flexible” pipe is a “stiff” structure and a direct tie-in to the pipeline may become an issue, if not addressed early enough during the execution of the project, when it can be too late to add mitigation structures, like intermediate tie-in spools, or to change significantly the routing of the risers and pipelines.
Operational Safety Risk Assessment in Offshore Oil Wells
Authors: Jaculli Marcelo A. , Colombo Danilo , Mendes José Ricardo P. , Marculino Cinara F. G. , Costa Beethoven G. dos S. 
Published: November 2019

Abstract
Identifying and analyzing hazards and their associated risks have been a major concern of the oil industry since the Piper Alpha incident in 1988, but techniques to assess risks were only explored further in the last decade after the incident in Macondo. It became clear that there were many hazards associated with oil exploration and exploitation activities; therefore, these hazards had to be identified and proper measures to contain their damage had to be put in place. This led to a development in existing risk analysis techniques such as bowtie diagrams, fault trees, Bayesian networks and Markov methods, but also hybrid techniques such as Markov chain Monte Carlo methods and fuzzy fault trees. In this work, we presented and discussed a literature review on these techniques, focusing on their contributions to the oil industry, as well as existing legislation and standards concerning safety. After comparing advantages and disadvantages of these techniques, we proposed a methodology using graphs to assess the safety level associated to a standardized sequence of operations. This methodology is based on an ontology of operations (which provides standardization) and the concept of BIS (barrier integrated sets), which are sets of elements from a well that ensure safety to perform each operation. With available statistical data, or by using fuzzy sets to cover their absence, this methodology is able to quantify reliabilities and determine if a certain operation can be performed safely based on a risk acceptance criterion. In order to demonstrate this concept, we calculated the reliability of two primary BIS during the intermediate drilling phase and showed how the reliability changes based on the corresponding drilling operational sequence.
A Study of Ship’s Frictional Resistance in Extremely Shallow Water
Authors: Zeng Qingsong , Hekkenberg Robert , Thill Cornel 
Published: November 2019

Abstract
In ship model tests, a model-ship correlation line (e.g., the ITTC57 formula) is used to calculate the frictional resistance of both the ship and its scaled model. However, this line is designed for deep water and the effects of water depth is not considered. Research has been conducted to improve the correlation line in shallow water, but studies of the extremely shallow water case (depth/draft, h/T &lt; 1.2) are rare. This study focuses on the friction of two ship types in extremely shallow water, where the ship’s boundary layer cannot develop freely. The physical details are analyzed based on the data generated with Computational Fluid Dynamics (CFD) calculations. The results show that for certain ship types at the same Reynolds number, the frictional resistance becomes smaller when the water is shallower. The geometry of the ship, in addition to the Reynolds number, becomes essential to the prediction of ship’s friction in extremely shallow water. Therefore, this scenario is different from intermediate shallow and deep water, and the prediction method should be considered separately. The data and analysis shown in this study can help to improve the understanding and prediction of ship’s frictional resistance in extremely shallow water.
Numerical Study on Nonlinear Wave-Ice-Interaction
Authors: Hartmann Moritz , von Bock und Polach R. U. Franz , Ehlers Sören , Hoffmann Norbert , Onorato Miguel , Klein Marco 
Published: November 2019

Abstract
This paper investigates the fundamental question of nonlinear wave-ice interaction under level ice focusing on nonlinear wave propagation and dispersion of waves. Therefore, numerical investigations are performed to verify theoretically if nonlinearity takes place under level ice and if this can lead to intense wave events far away from the ice edge in order to provide an explanation for observed real-world ice break-ups. Therefore, nonlinear wave-ice interaction as well as the impact of the ice characteristics on this interaction will be investigated.
The direct numerical simulations of the nonlinear wave propagation under solid ice are performed within the Nonlinear Schrödinger Equation (NLSE) framework. The Peregrine breather solution is applied to represent exact solutions of the NLSE for a nonlinear wave group. The application of such a nonlinear wave group is predestined for the verification of occurring nonlinear wave-wave interaction below the ice sheet. For the definition of wave and ice parameters in the simulation setup, the results of the presented parameter study are used. The parameters are analyzed regarding relevant characteristics of nonlinear wave-ice interaction and wave propagation. By assuming constraints with respect to physical consistency, the parameter range for the NLSE simulations can be narrowed.
The scope of this investigation is to provide a better understanding of the ice conditions required to observe nonlinear wave effects under level ice.
Evaluation of the Temperature Effect on the Viscoelastic Responses of Flexible Risers
Authors: Liu Junpeng , Ma Jinsheng , Vaz Murilo Augusto , Duan Menglan 
Published: November 2019

Abstract
Mechanical behavior of flexible risers can be challenging due largely to its complex design generating strong nonlinear problems. Nonlinear material properties, as one of them, from polymer layers dominate the overall viscoelastic responses of flexible risers which may play an inevitable role on the global analysis in deepwater application. An alternative to predict the viscoelastic behavior comprising of the time domain and the frequency domain has been proposed recently by the authors (Liu and Vaz, 2016). Given the fact that polymeric material properties are temperature-dependent and that the temperature profiles in flexile risers vary continuously in both axial and radial direction, the temperature of the internal hydrocarbons must affect the viscoelastic responses. However, such phenomenon dose not draw much attention in previous studies. This paper presents an improved model for overcoming some drawbacks in the proposed model involving assumption of steady temperature distribution in polymer layer and no gap appearance between the adjacent layers. The computing method of model is developed by using a step by step test approach. Consequently, some important parameters like equivalent axial stiffness, contact pressure or gap between the near layers, and force-deformation relationship can be observed. Parametric studies are conducted on the axisymmetric viscoelastic behavior of flexible risers to study the role of input temperature and loading frequency. Results show that equivalent axial stiffness given by the improved model is smaller than before. It can also be found that the gap between metal layer and polymer layer appear easily and increases as time goes on.
Numerical Modelling of Net Motion in Waves and Current Using CFD
Authors: Martin Tobias , Kamath Arun , Bihs Hans 
Published: November 2019

Abstract
The structural and environmental challenges in the operation of marine fish cage structures, in particular in the open sea, can accurately be determined if the fluid dynamics in and around the whole system is studied. An important part of the system represents the porous net which encloses the fish. In this paper, a numerical model for the determination of the deformed shape of nets under consideration of hydrodynamic loads and elastic twines is elaborated. It is a quasi-static approach based on force equilibria at the knots and geometrical constraints. The missing time step restriction leads to an overall less costly computation. The fluid around the net is calculated using a two-phase CFD model. The focus of the research is on the calculation of fluid forces on the net and the analyses of the nets motion in current and waves.
The Wave Climate of the Southern Ocean
Authors: Young Ian R. 
Published: November 2019

Abstract
An analysis of the wind and wave climate of the Southern Ocean is provided based on a combination of more than 30-years of satellite altimeter data plus insitu buoy measurements at 5 locations in the Southern Ocean. The analysis shows that the Southern Ocean is a unique environment where there are strong winds year-round which blow over exceptionally long distances. This unique situation results in spectral forms which are not seen in any other oceanic basin.
Estimation and Comparison of Accuracy in Various Data Resolutions on Optimal Ship Routing Across the North Pacific Ocean
Authors: Sasa Kenji , Fujimatsu Takuya , Chen Chen , Shoji Ruri 
Published: November 2019

Abstract
The amount of maritime cargo has been increasing for several decades. However, most seafarers have been shifting from lifetime employment to temporary employment. This may result in the ships lacking the adept techniques of seafarers, which significantly increases the reliance and importance of operational support systems. There are many studies on optimal ship routing, but its accuracy has not been discussed sufficiently. Especially, the grid point value on the weather database is the most important factor to discuss regarding its accuracy. In the field of meteorology, these databases have been improved to include global data in recent decades. In this study, the simulation results are compared to know the influence to the accuracy if the spatial and time resolutions vary in each condition. Optimal ship routing is computed using the isochrone method, which is one of the major methods of route analysis. Numerical simulations are conducted for a container ship between Tokyo and Los Angeles, with the weather databases of National Centers for Environmental Prediction (NCEP) and National Oceanic and Atmospheric Administration (NOAA). It is known that there are no significant differences between each resolution setting. However, the optimal voyage routes are different if the ship avoids high waves or strong winds in any direction. The accuracy is more influenced by the maneuverability in rough seas than the spatial and time resolutions of the weather databases. Accordingly, optimal ship routing must consider the actual maneuvering and speed loss theories, besides the development of a meteorological database.
A Study of Hydrate Inhibition for Deepwater Gas Field Development
Authors: Yi Hualei , Hao Yun , Zhou Xiaohong 
Published: November 2019

Abstract
For deepwater subsea tie-back gas field development, hydrate tends to be formed in deepwater subsea production system and gas pipeline due to high pressure and low temperature. Based on the gas field A development, this paper studies the selection of hydrate inhibitors and injection points, i.e. different injection points with different inhibitors. Transient and steady flow simulations are performed using the OLGA software widely used for multiphase flow pipeline study in the world. The produced water flow rate affects the hydrate inhibition in case of well opening, including cases of different times with different water temperatures. This paper presents the calculation of the maximum inhibitor injection rate in the subsea pipeline by taking the whole production years into consideration. The measures on hydrate remediation are taken by quickly relieving the subsea pipeline pressure from wellheads and the platform according to different hydrate locations. Now more and more deepwater gas fields are developed in South China Sea and around the world. The experience obtained from the gas field A development will benefit the hydrate inhibition for future deepwater gas field development.
Experimental Study of Drillstring Dynamics Using a High-Speed Camera As a Non-Invasive Motion Sensor
Authors: Wiktorski Ekaterina , Khatibi Milad , Geekiyanage Suranga , Sui Dan , Time Rune W. 
Published: November 2019

Abstract
In the last decades, drilling industry has been developing solutions to overcome challenges that impede drilling of long directional wells as excessive friction, poor directional control, narrow drilling windows, etc. One of the problems that is identified, yet not solved is the drillstring vibrations. Drillstring vibrations result in low ROP, fatigue and failure of the drillstring elements and weakened wellbore integrity. They are often detected through surface symptoms, as large surface WOB fluctuations (axial vibrations), torque and RPM fluctuations (torsional vibrations), reduced ROP, pressure fluctuations, rig/top drive shaking, etc.
To control vibrations, a good understanding of basic mechanisms of vibrations initiation and propagation is required. Therefore, this paper aims at the experimental investigation of the drillstring dynamics using a small-scale drilling rig constructed at the University of Stavanger. The experimental drilling rig is equipped with a WOB surface sensor, which works as a strain gauge, as well as RPM and torque encoder and other sensors. For a small-scale system, measurements of the surface sensors represent the combined responses of the whole rig structure, not just the drillstring. Therefore, more information to show drillstring dynamics (displacements and frequencies) is desired, besides surface measurement.
This paper presents experiments designed to detect vibrations of the drillstring using a high-speed camera, which in this study serves as an along-the-pipe downhole sensor. The paper also provides the image-processing algorithm that was developed to extract the signal from the images, digitize and normalize it. The high-speed camera has proved to be an accurate and practically noise-free displacement sensor.
As a part of this study, analysis of the captured frequencies and decaying amplitudes (damping) was performed for both the high-speed camera and the load cells data. It helped to evaluate whether the surface sensors are able to provide sufficient information about the downhole vibrations. We have seen that in the case where the drillstring interacts with the wellbore, the downhole vibrations are reflected to the surface. However, when the string hangs freely, surface and downhole sensors measure responses from different parts of the system. These conclusions are mostly valid for small-scale vertical systems, however, can also be considered for drilling shallow vertical wells/top sections.
FIV Energy Harvesting From Sharp-Edge Oscillators
Authors: Tamimi Vahid , Armin Milad , Shahvaghar-Asl Selda , Naeeni Seyed Taghi Omid , Zeinoddini Mostafa 
Published: November 2019

Abstract
The relative incompetency of rectangular galloping excavators against conventional circular VIV harvesters is already known. In this experimental study, the hydroelastic energy performances of new right-angle isosceles triangular cylinder against circular, square and diamond cross-sections are investigated. The triangular cylinder displays VIV or galloping type of response in four different symmetrical and unsymmetrical configurations tested. The results show the distinct higher overall galloping energy performance of the triangular cylinder in Config. 2 among other VIV and galloping harvesters. The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is employed to order the remaining tested cross-sections using the averaged and maximum values of the mechanical power and efficiency as criteria. The TOPSIS algorithm shows that the VIV diamond and circular harvesters stay at the second and third places of the energy performance, respectively. The preference value of the diamond and circular cross-sections are almost comparable but are less than half of that in Config. 2. In general, the sharp-edge cylinders display superior energy performance over circular cross-section. However, the axisymmetric circular cylinders, because of their omnidirectional performances, are more efficient in places with the varying flow direction.
Safe Operations of Bolted Connections in the Oil and Gas Industries
Authors: Langøy Morten A. , Hinderaker Rolf H. , Andersen Terje L. 
Published: November 2019

Abstract
The objective of this paper is to discuss the risk associated with fasteners used in the offshore industry. The intention is to suggest a way forward in establishing a robust system for management of fastener integrity on offshore installation, both topside and subsea, and thereby improve the safety level.
However, the large variation in design and use of bolted connections have to be analysed to identify the areas with the largest risk. Based on analysis of incidents reported to the Petroleum Safety Authority, Norway and analysis of industry standards and practices possible industry initiatives are identified.
Finite Element Analysis of the Effect of Twist on Chain Fatigue Performance
Authors: Jones Justin 
Published: November 2019

Abstract
Mooring chains may be installed with twist or become twisted during service. This paper describes an investigation of the effect of a range of twist angles on the fatigue life of studless chain through the use of detailed finite element analysis.
The analysis includes the local contact patch deformation and residual stress state that results from plasticity during the proof testing of the chain. The effect of high in-service tension resulting from storms that produces additional plasticity when the chain is loaded in the twisted state is also included. The change in fatigue life at the crown, inner bend and around the contact patch are assessed. Local to the contact patch the fatigue life calculation includes an assessment of the multiaxial stress state.
For small angles of twist the calculated fatigue life at the crown and around the contact increases and that at the inner bend sees a marginal reduction. At twist angles above 12 to 14 degrees per link the calculated inner bend and contact patch fatigue lives reduce markedly with increasing twist, but the crown fatigue life continues to increase.
Large Diameter Deepwater Gas Pipelines Subjected to Global Buckling Behavior
Authors: Antunes Bruno R. , Solano Rafael F. , Cardoso Carlos O. 
Published: November 2019

Abstract
In general, gas export pipeline designs have low restrictions concerning the flow assurance requirements, i. e., hydrate formation is not a great concern once processes in production platform facilities can significantly decrease the water content in the gas to be exported. Thus, these pipelines have only a small thickness of a single or multilayer anticorrosive coating and export gas at low temperatures. However, high pressures are required in order to overcome long distances and to increase the production flow rates.
Large diameter gas pipelines submitted to high pressures even with low associated temperatures can be susceptible to global buckling, mainly if the pipelines are simply rested on a seabed of low resistance. This scenario characterizes strictly the gas pipelines installed in Brazilian Pre-Salt fields, where currently a relevant amount of export lines is operating in these conditions. Post-installation and operating pipeline surveys have identified marks on seabed confirming the buckle formation in some gas pipelines. In addition, axial movements of end equipment (PLETs) have been also observed. These issues require at least a verification and confirmation of the assumptions and predictions made in detailed design phase.
This paper aims to present evaluations of the global buckling behavior of large diameter deepwater gas pipelines. Lateral buckles on very soft clayey seabed and displacements in ends and crossing locations are addressed in this work. Finally, numerical analyses confirm that gas pipelines structural integrity has not been jeopardized.