bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pipeline Regulations in the Norwegian Petroleum Industry: Experiences, Follow-Up and Statistical Summaries of Incidents
Authors: Sundby Trond , Anfinsen Kjell Arild 
Published: October 2017

The Petroleum Safety Authority Norway (PSA) is an independent government regulator responsible for safety, emergency preparedness and the working environment in the Norwegian petroleum industry.
Norway’s regulations for petroleum operations offshore and on land are risk-based, and give great emphasis to principles for reducing health, safety and environmental (HSE) risk. They have been developed over more than 40 years, changing from detailed prescriptive regulations in the early days to the present requirements, which are largely formulated in performance-based (functional) terms. They specify requirements for the various aspects, characteristics or qualities which a product, process or service must possess.
In our regulations there are requirements for reporting incidents and specifically to report on damages to load-bearing structures and pipeline systems. About 2900 incidents with risers and pipelines were reported on the Norwegian Continental Shelf (NCS) from 1975 to January 2017. Of these, 2/3 related to pipelines and 1/3 to risers, and they were of varying degrees of severity. The incidents with highest risk for personnel concerned risers and more than 80 reported major incidents involving flexible risers occurred in the period from 2000–2016.
This paper will briefly summarise the development of the regulations and give examples from the pipeline regulations and the way the PSA follows up the industry today. We will also present statistical data of incidents related to risers. Since the start of the trends in risk level project (RNNP) on the Norwegian Continental Shelf (NCS) in 1999–2000 there has been 84 reported riser incidents (classified as major in the PSA RNNP-project) where most of those incidents are related to flexibles. There has been no major accident related to risers on the NCS in the same period and very few leaks. 8 of 11 reported leaks for pipelines and risers within the safety zone has been from flexible risers, with relatively low leak rates.
Comparison of Field Measurement and Numerical Simulation of the T-Shaped Barge Motions During the Topside Floatover Installation
Authors: Yu Wentai , Li Huailiang , Zhu Shaohua , Wang Alan M. , Xie Peng , Luo Hanbing 
Published: October 2017

This paper presents the comparison of field measurement and numerical simulations of the barge motions in the successful floatover installation of one mega topside in Bohai Bay, China.
The motion measurements of the T-shaped floatover barge HYSY228 and the environmental field measurements were conducted to guide the entire floatover operation. The motion monitoring system can provide up to centimeter-level accuracy to monitor the six-degree-of-freedom barge motions. The environmental monitoring systems include one buoy system measuring the wave height, period and direction, an Acoustic Doppler Current Profilers (ADCP) for the profile current speed and direction, an anemometer, and a tidal gauge.
Numerical simulation is carried out for the barge motions in the standby stage of floatover installation in mooring condition. The motions of the barge and mooring force responses are obtained by the commercial code SESAM using the measured environmental data. Two different methods, Newman’s approximation and Second-order Transfer Function (QTF), are used to predict the second order wave force. The wave component (high frequency) and the second order component (low frequency) are discussed. Statistical results are compared with those from the field measurement. Fair well agreement is achieved.
Interference of Top Tensioned Risers for Tension Leg Platforms
Authors: Zhang Hanqing , Smith Derek 
Published: October 2017

Dry tree top-tensioned risers (TTRs) are widely used on floating production systems such as TLPs and Spars for drilling, completion, workover and production. The interference between neighboring TTRs is an important consideration which has a direct impact on the total TTR payload budget and the wellbay size for floater sizing and cost. Since the realistic sizing of a floater is essential towards the concept selection process for a field development, TTR interference should be addressed at the early stages of an offshore oilfield development. If the floater is a tension leg platform (TLP) and the field has strong current with associated extreme waves, riser interference may be very challenging and can have direct impact on riser design and the sizing and layout of the TLP. The waves and the oscillating motions of the TLP will have effects on riser interference. The oscillating motion of the TLP can excite the vibrational motion of the risers, and the wave-induced velocity of water particles and the motions of the risers with the movement of the TLP increases the relative flow acting on each riser. The combined effects will increase the deflection of the risers and thus the likelihood of riser interference. The industry has not seen an acceptable interference analysis approach yet which can account for the combined effects of current, waves, and TLP motions.
This paper proposes two engineering approaches for the interference analysis of top tensioned risers for tension leg platforms with the combined effects of current, surface waves, and associated floater motions being addressed.
Benefits and Deep Water Install Ability Challenges of Residual Curvature Method for Lateral Buckling Mitigation
Authors: Karjadi Erwan , Cooper Phil , Smienk Henk , Kortekaas Ferry 
Published: October 2017

One way to control lateral buckling in the operation phase for High Pressure High Temperature (HPHT) pipelines is by deliberately introducing residual curvature sections at intervals along the pipeline by adjusting the straightener settings of the pipelay tower, as described in a patent held by Statoil [1]. This method has been applied with reel-lay installation for a number of shallow water pipelines in Europe (Statoil’s Skuld project and Total’s Edradour project).
The paper presents the benefits as well as the feasibility of the use of Residual Curvature Method (RCM) to control lateral buckling for deep water applications which involves high top tension in the overbend and high pressure and twist of the RC section in the sagbend. The study cases consider the application of the method for pipelines in 1850m water depth which are pushing the pipe top tension close to the limit of the capacity of the tensioners of Heerema Marine Contractor’s (HMC) Reel-lay vessel the Aegir. There are some challenges of the application of the residual curve method for deep water pipelines. Due to high top tension, some potential issues are investigated during lowering of the curved section from the straightener, passing the tensioners and through the J-lay tower into the water to the seabed. Detailed analyses have been performed to check the interaction of the residual curved pipe section against the tensioners (the effect of the squeeze load on the RC section) and to assess the maximum bending moment generated when the residual curved section is under high top tension below the tensioners against the Load Controlled Condition (LCC) for local buckling bending moment limit. Another consideration is the increase of hydrostatic pressure in deep water which could limit the allowable bending moment in the sagbend when lowering the curved sections to the seabed. Discussions are presented to the feasibility of the concept including the proposed ways of mitigation for the aforementioned potential issues.
The paper will also show an improved prediction of pipe twist/roll by comparing a published analytical 2D plane solution against the 3D FEA model prediction. The improved prediction, which considers the out of plane bending component of the pipe catenary, results in an increase of pipe twist in the sagbend section. This reduces the bending moment in the residual curved section when entering the sagbend and increases the probability to roll the curved section over to the horizontal plane on the seabed.
Optimising Foundation Skirt Geometries for Reliable Foundation Capacity and Installation
Authors: Bransby M. F. , O’Driscoll D. , Zhu H. , Randolph M. F. , Drummen T. 
Published: October 2017

Increasing numbers of subsea structures related to wells and pipelines are being placed on the seabed as part of typical subsea or tie-back developments. Given the proliferation of these structures and the marginal cost of offshore developments, controlling installation and fabrication costs for subsea structures can be key to project viability. Skirted mudmats are often the most cost-effective foundation type, and particular additional design focuses on optimising their cost by minimising foundation weight and installation time.
Subsea foundations must be designed to withstand all applied loads during their design life (e.g. during set-down, tie-in, hydrotest, operation etc.) with suitable reliability. Using skirts, peripheral or internal, to improve the sliding resistance is an efficient solution provided the self-weight of the subsea structure on set-down is sufficiently large to ensure installation of the skirts (even for the strongest likely seabed conditions), but can lead to significant cost increases if additional ballast is required to ensure this.
The paper examines how foundation skirt geometries can be optimised in order to provide sufficient foundation in-place capacity whilst minimising the amount of self-weight required for their installation. Parametric studies are presented that show how the sliding capacity of individual skirts is affected by the weight of the structure, and also the spacing and position within the foundation plan.
Prototype Reynolds Number VIV Tests on a Full-Scale Rigid Riser
Authors: Yin Decao , Lie Halvor , Baarholm Rolf J. 
Published: October 2017

Slender offshore structures in deep water subjected to currents may experience vortex-induced vibrations (VIV), which can cause significant fatigue damage. Extensive experimental researches have been conducted to study the VIV in the past several decades. However, most of the experimental works have small-scale models and relatively low Reynolds number (Re) - ‘subcritical’ or even lower Reynolds number regime. There is a lack of full understanding the VIV in prototype Re flow regime. Applying the results with low Re to a full scale riser with prototype Re might have uncertainties due to the scaling effects. In addition, the surface roughness of the riser is also an important parameter, especially in prototype Re regime.
In present study, two full-scale rigid riser models with different surface roughness ratios were tested in the towing tank of MARINTEK in 2014. Stationary tests, pure cross-flow (CF) free oscillation tests and forced/controlled motion tests were carried out.
Several conclusions could be made:
• The drag coefficient is dependent on the Re number and surface roughness ratio.
• At critical and supercritical flow regimes, the displacement amplitude ratio is less sensitive to Re than that at lower Re. The displacement amplitude ratio in subcritical flow regime is significantly larger than that in critical and supercritical flow regimes.
• Two excitation regions for the ‘smooth riser’ and one excitation region for the ‘rough riser’ are identified.
On the Comparison of the Dynamic Response of an Offshore Floating VAWT System When Adopting Two Different Mooring System Model of Dynamics: Quasi-Static vs Lumped Mass Approach
Authors: Cevasco Debora , Collu Maurizio , Hall Matthew , Rizzo Cesare M. 
Published: October 2017

The interest in floating offshore wind turbines (FOWT) has been growing substantially over the last decade and, after a number of prototypes deployed [1], the first offshore floating wind farms have been approved and are being developed. While a number of international research activities have been conducted on the dynamics of offshore floating HAWT systems (e.g. OC3-Phase IV2, OC4-Phase II3), relatively few studies have been conducted on floating VAWT systems, despite their potential advantages [2]. Due to the substantial differences between HAWT and VAWT aerodynamics, the analyses on floating HAWT cannot be extended to floating VAWT systems.
The main aim of the present work is to compare the dynamic response of the FOWT system adopting two different mooring dynamics approaches. Two version of the in-house aero-hydro-mooring coupled model of dynamics for VAWT “FloVAWT” [3] are used: one which adopts a mooring quasi-static model, and solves the equations using an energetic approach [4], and a modified version of FloVAWT, which uses instead the lumped-mass mooring line model “MoorDyn” [5]. The floating VAWT system considered is based on a 5MW Darrieus type rotor supported by the OC4-Phase II3 semi-submersible.
The results for the considered metocean conditions show that MoorDyn approach estimate larger translational displacements of the platform, compared to the quasi-static rigid approach previously implemented in FloVAWT. As expected, the magnitudes of the forces along the lines are lower, being part of the energy employed for the elastic deformation of the cables. A systematic comparison of the differences between the two approaches is presented.
Long Term Analysis of Semi Submersible Offset
Authors: Sandbakken Sindre S. , Haver Sverre , Larsen Kjell 
Published: October 2017

During the design of risers, it is necessary to calculate the 100-year (ULS) top-end motion with reasonable accuracy. The ULS offset is usually taken as the most probable 3-hour maximum response in a storm modeled with 100-year wind and 100-year waves when current forces are neglected. This design approach is assumed to be conservative. In this paper, the level of conservatism is considered by performing a Peak Over Threshold (POT) and All Sea States (ASS) stochastic long term analysis.
The 3-hour maximum offset is assumed to be Gumbel distributed for the POT and ASS analysis. Gumbel parameters are estimated using method of moments for all metocean combinations. Response surfaces are established as a function of wind speed, W, significant wave height, Hs, and spectral peak period, Tp, to represent the short term variability of the response problem. The long term distribution of the most probable maximum response is established for the POT analysis. Similarly, a long term probabilistic model for W, Hs and Tp is established for the ASS analysis. Finally, the long term analyses are performed by combining the short term and long term variabilities using IFORM.
Soil-Pipe Interaction Models for the Simulation of Buried Steel Pipeline Behaviour Against Geohazards
Authors: Sarvanis Gregory C. , Karamanos Spyros A. , Vazouras Polynikis , Dakoulas Panos , Mecozzi Elisabetta , Lucci Antonio 
Published: October 2017

Hydrocarbon pipelines constructed in geohazards areas, are subjected to ground-induced actions, associated with the development of severe strains in the pipeline and constitute major threats for their structural integrity. In the course of pipeline design, calculation of those strains is necessary for safeguarding pipeline integrity, and the development of reliable analytical/numerical design tools that account for soil-pipe interaction is required.
In the present paper, soil-pipe interaction models for buried steel pipelines subjected to severe ground-induced actions are presented. First, two numerical methodologies, (simplified and rigorous) and one analytical are presented and compared, followed by an experimental verification; transversal soil-pipe interaction is examined through full-scale experimental testing, and comparisons of numerical simulations with rigorous finite element models are reported. Furthermore, the rigorous model is compared with the results from a special-purpose full-scale “landslide/fault” experimental test in order to examine the soil-pipe interaction in a complex loading conditions. Finally, the verified rigorous model is compared with both the simplified models and the analytical methodology.
Experimental Study of Viscous Cargo Behaviour and Investigation on Global Loads Exerted on Ship Tanks
Authors: Baudry Virginie , Rousset Jean-Marc 
Published: October 2017

The LiquefAction project is dedicated to the study of cargo liquefaction, especially to understand the inception of this phenomenon and its effects on bulk carrier stability. Both numerical and experimental approaches are set-up to simulate the behaviour of specific ores in various modes of motions.
This paper is dealing with forced motion tests of a tank filled with two highly viscous fluids. The tank is a bulk carrier hold model and a hexapod platform is reproducing the ship motions. Free surface evolutions as well as global loads are analysed.
Some preliminary conclusions are given with respect to the filling ratio, the fluid viscosity and type of motions.
Experimental Study on the Vortex-Induced Motions (VIM) of a Semi-Submersible Floater in Waves
Authors: Maximiano António , Koop Arjen , de Wilde Jaap , Gonçalves Rodolfo T. 
Published: October 2017

Recent studies suggest that the vortex-induced motions (VIM) of a semi-submersible found in model tests over-predicts the response in the field, which may lead to an over conservative design of the mooring and riser system. Within the Vortex Induced Motion Joint Industry Project (VIM JIP), run by MARIN and University of São Paulo (USP), possible reasons for this over-prediction are investigated using model tests and CFD [1–6]. A model test campaign was carried out at MARIN to test different candidates that might explain the observed differences. The results obtained with an air bearing setup regarding damping, mass ratio, draft variations and sinusoidal tow velocities, have been published elsewhere [6]. The present publication focuses on the influence of waves on the VIM response.
The model was a generic bare hull semi submersible with four rounded square columns at scale 56.5. A simplified mooring system consisting of four springs was designed to match the desired natural period in the sway and yaw direction. The model was towed at different velocities, corresponding to the range of reduced velocities where the highest response is expected. A VIM tow test campaign was carried out in calm water as a benchmark. The model was then tested at 7 different wave-current conditions, and the results are compared with the benchmark case.
The results suggest that two factors are important for VIM response in waves: the wave height, and the relation between wave and current direction. Comparing to calm water conditions, a reduction of 15% on the peak nominal response was found for a smaller sea state (HS = 2m, TP = 10s), however with a higher significant wave height (HS = 4m, TP = 10s) the peak nominal response was reduced by 30%. Depending on the combination of current-wave direction, the influence of the same sea state (HS = 4m, TP = 10s) on VIM response can be negligible (transverse seas) or result in a 30% reduction of the peak nominal response for collinear sea and current. This is a relevant finding since most research on the topic has focused on collinear conditions, and VIM tests in waves with transverse or oblique conditions are rare [7–9].
Comparing the calm water VIM response obtained with the air bearing setup, published in [6], with the soft mooring configuration reported here, the latter shows a generally smaller response, with a narrower lock in region. Nevertheless the peak response is found to be similar for both experimental setups.
Heat Loss of Heated Deck Elements in Cross-Flow Wind
Authors: Peechanatt Jino , Kvamme Bjarte O. , Gudmestad Ove T. , Amith Yaaseen A. 
Published: October 2017

In recent years, there has been unprecedented interest shown in the Arctic region by the industry, as it has become increasingly accessible for oil and gas exploration, shipping, and tourism. The decrease in ice extent in the Arctic has renewed the interest in the Northern Sea route, necessitating further research to evaluate the adequacy of the equipment and appliances used on vessels traversing in polar waters.
The introduction of the Polar Code by the International Maritime Organization (IMO) attempts to mitigate some of the risks endangering the vessels in Polar waters. The Polar Code is scheduled to take effect on 01.01.2017, and applies to all vessels traversing in polar waters. One of the requirements in the Polar Code is that means shall be provided to remove or prevent accretion of snow and/or ice from escape routes, embarkation areas and access points. Even though, prior to the formulation of Polar Code, the requirement for de-icing the deck surfaces on vessels already exists, the suitability of the equipment currently in use is debatable. Large amounts of energy is required to maintain an ice-free surface, which is not desirable economically or environmentally, due to the substantial increase in fuel consumption.
In this study, a heated deck element manufactured by GMC Maritime AS is subjected to cross flow wind of 5 m/s, 10 m/s and 15 m/s at various sub-zero temperatures in GMC Maritime AS’s climate laboratory in Stavanger, Norway. The deck element is rated to 1400 W / m2, and is one of the designs provided by GMC Maritime AS. The power consumption of the deck element is measured and compared to theoretical heat loss calculations. Large discrepancies between the measured power consumption and the theoretical heat loss were discovered, indicating the need for further studies on the matter.
As part of SARex Spitzbergen 2016, a search and rescue exercise conducted off North Spitzbergen, heated deck elements on board the Norwegian Coast Guard Vessel KV Svalbard were studied and are discussed in this paper. The heating elements in the deck elements were designed to specifications at the time of commissioning, but proves insufficient when the vessel is in transit or exposed to slight winds, allowing snow and ice to accumulate on the surface.
Finally, suggestions for a more energy efficient design of deck elements are made, as the current designs are found to have potential for improvement, especially due to the lack of insulation between the deck elements and the hull of the vessel.