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Abdalla B.,J P Kenny Pty Ltd. | Mei H.,MCS Kenny
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2013

For deep water pipeline end manifold (PLEM) subject to complex loading conditions, a combined 3D finite element (FE) model has been developed by the authors to determine the foundation bearing capacity by studying the interaction between individual parts, including the PLEM structure, flowline, mudmat and soil. The advanced numerical techniques have proven that the resulting factor of safety against bearing failure is higher when compared to the classical approach given in API-RP-2A/2GEO. However, the minimum required safety factor of 2.0 is not reached. Therefore, risk assessment using reliability analysis becomes mandatory to assess the probability of failure of the mudmat. As an input to the risk assessment, this paper presents an investigation of the system's modes of failure and failure consequences on the environment and project cost. Using the developed 3D FE model, plausible excessive loads beyond design considerations are applied until a failure in soil foundation occurs. Then, loads are increased until the capacity of structural and mechanical components in the system is reached putting the containment of carried hydrocarbons at risk. A direct relationship between the hydrocarbon temperature and the capacity of structural/mechanical components is developed to evaluate the system flexibility and resistance to induced excessive deformations. The paper demonstrates the advantages of numerical techniques in evaluating the ultimate capacity of a PLEM structure and foundation soil system. The methodology can be used in the design of a new system or to assess the stability of an existing system under future loadings. Copyright © 2013 by ASME.

Pistani F.,MCS Kenny | Thiagarajan K.,University of Western Australia
Ocean Engineering | Year: 2012

A sloshing experiment has been setup in order to carry out analysis on the behaviour of LNG (Liquefied Natural Gas) tanks on board of marine vessels. The experiment aimed to measure with accuracy the high pressure generated during the impacts of the fluid in the case of rectilinear sinusoidal motion in the direction of sway. A two-dimensional tank model has been used for this purpose. The pressures due to fluid sloshing are measured at several locations along the tank boundaries together with the position of the tank and acquisition of images of the flow. This paper describes the experimental procedures that have been put in place to acquire the data and ensure its quality. The problems encountered during the activity are illustrated in detail in order to provide useful indications to other researchers. The different types of impact observed during the experiment, the characteristics of the measured pressures and the implementation of an algorithm for their correct identification are discussed in detail. © 2012 Elsevier Ltd.

Williams D.,MCS Kenny
Proceedings of the Annual Offshore Technology Conference | Year: 2010

As exploration activity in deepwater and harsh environment regions, and associated vessel costs, increase so too does pressure on drilling contractors and operators to accurately assess the limitations of vessels and drilling equipment. As a result there is a requirement for more refined methodologies and finite element models to verify the operability of drilling riser systems in these environments. The efficiency of a drilling riser system for connected operations will generally be most influenced by the current regime onsite as this will influence the vessel offsets and nominal flex joint angles. However, as vessel offset from the nominal position increases, the vessel dynamics become increasingly important in the determination of operability limits. Likewise for the storm hang-off, deployment (including both conductor and casing deployment) and retrieval scenarios the accurate assessment of system response is critical to identifying operability windows. For harsh environment operations the operability and efficiency of the system is a function of both riser component limitations and vessel response characteristics. As a result detailed analysis considering both system response screening (involving estimation of downtime due to extreme weather events) and irregular sea analysis of riser response is required. In addition, an iterative design approach is required in order to balance the competing design drivers associated with connected operations, storm hang-off, riser recoil, deployment and vessel drift-off and resultant weak point response. This operability assessment requires a detailed model of the riser system to accurately predict the response. This model needs to account for the nonlinear response of riser tensioners, influence of wellhead, conductor and casing, nonlinear soil interaction, detailed storm hang-off arrangements and associated clashing and interference issues. In addition to refined FE models, a detailed knowledge of the metocean data for the region of interest is required. This metocean data includes detailed seastate scatter diagrams and current profiles accounting for seasonal directional variation. This paper outlines the key issues associated with the modeling and analysis techniques for drilling riser systems intended for deepwater and harsh environment locations such as Atlantic Margin, offshore Norway and Offshore Canada. In addition a number of conservatisms in current practice are identified and optimizations are outlined. Copyright 2010, Offshore Technology Conference.

Qiu L.,MCS Kenny | Lee L.,MCS Kenny
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2013

The method of pulling a steel catenary riser (SCR) through a steel tube (termed as a pull tube) is common practice for deepwater riser tie back applications. Vortex-induced vibration (VIV) of such a system is complex. VIV analysis programs, such as Shear7 [1], are suitable only for a single, chain-like structure. The application of such a software tool in VIV design of the SCR-pull tube system requires careful consideration of a number of structural and hydrodynamic factors. This paper presents a methodology for VIV analysis of the combined structural system of the SCR with the pull tube. Firstly, the entire SCR-pull tube system is modeled with the finite element program Flexcom [2]. The modes are then calculated for the entire structure with program Modes [3]. Afterwards, the structural nodes are rearranged for VIV analysis with Shear7. The pull tube is secured on the platform through a number of guides on the truss structure of the hull. The diameter of the pull tube is much larger than that of the SCR, and the pull tube is much stiffer in bending than the SCR is. If the entire structure is analyzed with Shear7, the mode for the pull tube (a mode involving a large motion of the pull tube section), which is very high in order, would be embedded in the analysis. It makes sense to single out the pull tube mode for study as if it is the first mode. A computer program, named as V-Span [4] for subsea span VIV analysis, is used to analyze both in-line and cross-flow VIV of the pull tube. A numerical example is presented to demonstrate this methodology. This is a deepwater SCR, which has a diameter of 9 inches. The water depth is 6,300 ft. The pull tube is 640 feet long and 20 inch in diameter. Both the loop-eddy and background currents are analyzed. The fatigue damage resulted from both in-line and cross-flow VIV is estimated. Copyright © 2013 by ASME.

Connolly A.,MCS Kenny
Hart's E and P | Year: 2011

MCS Kenny has developed a new advanced software called Flexcom 8 specifically for oil and gas operations. Flexcom 8 is the company's next-generation riser design and analysis software that delivers a step change in how riser engineering design and analysis is performed. The enhancements provided by this new version lead to a better design that supports the industry's increasing focus on improved process safety, better predictability, and greater knowledge of utilization and integrity during operations. The new user interface has been created using the latest software development technologies, including .NET Framework and Windows Presentation Foundation (WPF). Flexcom 8 represents a fully integrated engineering environment, with all of the necessary tools available in one box. A structural preview facility is available while model creation is in progress, which continually updates to reflect alterations and augmentations to the model. The software is designed to simplify the quality assurance process.

Francis K.,MCS Kenny
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2011

This paper presents a comparison of the various methods for combining bimodal wave fatigue damage for flexible risers attached to floating production platforms. Finite Element Analysis is used to determine the riser response, stress ranges, and fatigue damage. The resulting stress ranges or damages are then combined via the various methods outlined in DNV-RP-F204 [2] and the RealLife JIP [3]. A base case of the fatigue damage with swell and sea analyzed together is compared against each method for summation of the damages to determine the level of conservatism in each method. A recommendation of the most appropriate method of combining swell and sea wave damages is presented in this paper. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).

Pistani F.,MCS Kenny | Brooker D.,MCS Kenny
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2014

The design approach for the analysis of a riser turret mooring system (RTM) connected to a FPSO is presented here. The design was carried out with the use of numerical models developed with Ariane and Orcaflex software packages. Ariane has been used as a screening tool while the model developed with Orcaflex was used for detailed analysis. The succesful validation of the models against existing experimental tests helps to avoid the repetition of a model test campaign for design of new systems. An original solution to overcome the limitations of the mooring software Ariane has been developed and used for mooring analysis. This paper describes the development of the numerical models highlighting the original features, the validation with the model tests and discusses some of the main results. Copyright © 2014 by ASME.

Chaudhury G.,MCS Kenny | Chakkarapani V.,MCS Kenny
19th Offshore Symposium 2014: Emerging Technologies in Offshore Drilling and Production | Year: 2014

In order to achieve overall cost effectiveness, all FLNG (Floating Liquid Natural Gas) projects must use large volume of deep sea cold water for their cooling process. This has prompted FLNG projects hanging several risers (about 20 to 30 inch diameter) vertically straight down from the platform to a depth between 500 to 1000 feet. Static and dynamic motion analyses of these risers reveal conflicting design requirements. Low stiffness and light weight help to decrease stress and moment reaction on the FLNG vessel and riser, while associated large motions cause problem with interference between risers. High stiffness and heavier weight help to increase minimum bend radius (MBR) and decrease the riser motions and interference. Weight mass affects the dynamics but provides valuable restoring moment thus reduces static displacement due to current forces. Present work describes details of a concept development study, based on the pertinent design parameters, static and dynamic tuning of riser connection, and the development of an innovative solution. This study has demonstrated that simplest alternative solution is a single caisson type riser employing available large diameter (60 to 70 inch) pipes with different options of connections at the platform. Other potential materials of choice can be Glass Fiber Reinforced Plastic (GFRP), High Density Polyethylene Pipe (HDPE), and high strength steel, or a hybrid combination of steel with titanium or aluminum. Various options of constructions and installations have also been examined. Copyright © (2014) by the Society of Naval Architects and Marine Engineers Texas Section All rights reserved.

Anderson K.,MCS Kenny | O'Connor M.,MCS Kenny
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2012

Flexible riser configurations in harsh environments require riser buoyancy in order to decouple vessel induced motions from the seabed interface. This is achieved through either wave (distributed buoyancy) or S (subsea buoy) solutions. In the UK sector of the North Sea circa 30% of all floating production system field developments utilise subsea buoys in Lazy-S configurations. The majority of these fields have been in service for many years and designed prior to the widespread adoption of current industry standards, the analytical rigour available today, and better characterisation of the metocean environment. In many cases original system design has also been for 50yr return period conditions, compared to the specified 100yr return period events required in todays codes and standards, e.g. ISO 13628-2 [1]. Therefore, when replacement riser or life extension work is performed on existing structures or new developments are being designed there can be significant challenges in confirming the applicability of traditional system configuration designs. The principal challenges with these configurations is minimising sag bend compressions driven by differential buoy vs. vessel motions and maintaining the riser or umbilical minimum curvature and compression criteria at the seabed touch down. The latter point is a particular problem for umbilicals routed via Lazy-S configurations owing to their relatively low weight and stiffness, and constraining MBR criteria. This paper considers the applicability of Lazy-S configurations as a solution to modern harsh environment field developments and the evolution in Lazy-S system design to address the design challenges with particular emphasis on the TDP response. Copyright © 2012 by ASME.

Al-Showaiter A.,MCS Kenny | Al-Showaiter A.,Dalhousie University | Taheri F.,Dalhousie University | Kenny S.,Memorial University of Newfoundland
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2011

The aim of the present study is to develop numerical modeling procedures to simulate and study the effect of girth weld induced residual stresses and geometric imperfections on the behavior of conventional carbon steel oil and gas pipelines. The effect of welding residual stresses was obtained through computational simulations of the multipass girth weld process. The numerical procedures were calibrated using available pubic domain data on stainless steel. The methodology for conducting the welding simulation is presented. A parametric analysis was conducted using the finite element methods to evaluate the effects of welding residual stress due to girth welding processes, joint-to-joint misalignment associated with the girth weld, internal pressure, axial force, and diameter to wall thickness ratio on the local buckling response of pipelines. The pipeline moment-curvature response was examined to determine the influence of these parameters. For the parameters investigated, results from this study have demonstrated the significance of residual stress state due to welding processes and girth weld misalignment on the local buckling response of pipelines subjected to monotonic loading with combined stress state. © 2011 American Society of Mechanical Engineers.

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