Vortex Induced Vibrations of Deep Water Risers: Sensitivity to Current Profile, Shear and Directionality

2014 ◽  
Author(s):  
Rafael Vergara Schiller ◽  
Marcelo Caire ◽  
Pedro Henrique Affonso Nóbrega ◽  
Elizabeth Passano ◽  
Halvor Lie
Keyword(s):  
Deep Water ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Sensitivity Analyses ◽  
Current Profile ◽  
Boundary Current ◽  
Gas Industry ◽  
Vortex Induced Vibrations ◽  
Se Brazil

Slender offshore structures such as risers experience vortex induced vibrations (VIV) when they are exposed to currents and accumulate significant fatigue damage through that process. VIV will depend on several structural properties of the riser and on the current profile that the structure is exposed to. In deep water regions, risers will be subject to intricate circulation systems that impose currents profiles which may vary in intensity, shear and direction throughout the water column. The increased complexity of currents will make the prediction of VIV more difficult and represents a clear challenge to the Oil and Gas Industry. The objective of this study is to investigate how selected properties of a current profile affect the development and excitation of VIV for a deep water tensioned riser. We employ a semi-empirical frequency-domain program to perform a series of numerical sensitivity analyses where the riser model is subject to current profiles that vary in complexity and include uniform profiles, linearly-sheared profiles and more realistic profiles that represent offshore boundary current regimes from SE Brazil. We address the sensitivity of the VIV response to current intensity, shear and directionality. Our results demonstrate that those properties of the current profile have significant influence on the range of VIV modes that are excited and on the VIV response. Overall, uniform profiles produced the largest responses and the linearly-sheared profiles demonstrated the large range of VIV modes that can be excited. The realistic profiles also excited a broad range of VIV modes and variations between the profiles produced changes in the VIV response. This study highlights the need to further understand how complex current profiles in the offshore region affect VIV development in comparison to simpler profiles that are recurrent in model test conditions.

Tubarão Martelo Field Riser System: Shallow Water Challenging

2015 ◽  
Author(s):  
Elton J. B. Ribeiro ◽  
Zhimin Tan ◽  
Yucheng Hou ◽  
Yanqiu Zhang ◽  
Andre Iwane
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Oil And Gas ◽  
Vertical Motion ◽  
Oil And Gas Industry ◽  
System Configuration ◽  
Wave Load ◽  
Gas Industry ◽  
Campos Basin ◽  
Water Problem

Currently the oil and gas industry is focusing on challenging deep water projects, particularly in Campos Basin located coast off Brazil. However, there are a lot of prolific reservoirs located in shallow water, which need to be developed and they are located in area very far from the coast, where there aren’t pipelines facilities to export oil production, in this case is necessary to use a floating production unit able to storage produced oil, such as a FPSO. So, the riser system configuration should be able to absorb FPSO’s dynamic response due to wave load and avoid damage at touch down zone, in this case is recommended to use compliant riser configuration, such as Lazy Wave, Tethered Wave or Lazy S. In addition to, the proposed FPSO for Tubarão Martelo development is a type VLCC (Very Large Crude Carrier) using external turret moored system, which cause large vertical motion at riser connection and it presents large static offset. Also are expected to install 26 risers and umbilicals hanging off on the turret, this large number of risers and umbilicals has driven the main concerns to clashing and clearance requirement since Lazy-S configuration was adopted. In this paper, some numerical model details and recommendations will be presented, which became a feasible challenging risers system in shallow water. For instance, to solve clashing problem it is strictly recommended for modeling MWA (Mid Water Arch) gutter and bend stiffener at top I-tube interface, this recommendation doesn’t matter in deep water, but for shallow water problem is very important. Also is important to use ballast modules in order to solve clashing problems.

scholarly journals ON STANDARDIZATION OF LABORATORY SOIL TESTING IN OFFSHORE GEOTECHNICAL SURVEY

Gruntovedenie ◽  
2021 ◽  
Vol 1 (16) ◽  
pp. 16-52
Author(s):  
E.A. Voznesensky ◽  
◽  
A.S. Loktev ◽  
M.S. Nikitin ◽  
◽  
...  
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Soil Testing ◽  
National Standard ◽  
Gas Industry ◽  
Code Of Practice ◽  
Complete Section ◽  
Testing Practice ◽  
Russian Soil

Issues of laboratory soil studies standardization in offshore geotechnical survey are discussed in connection with the end of expertise of two new regulative documents – new edition of the Code of practice and Russian national standard developed on the basis of international ISO standard. Since these documents of different level belong also to different categories (geotechnical survey and oil and gas industry), the authors analyze their interrelation and consistency, from one hand, and the preparedness of Russian soil testing practice to implementation of the new standard which results from harmonization with international ones, from the other. Complete section of the standard draft related to soil laboratory testing is presented, preceded by commentary on some important issues regarding the implementation of its specific methodic statements. It is concluded that the new national GOST draft «Petroleum and natural gas industries. Specific requirements for offshore structures. Marine soil investigations» developed on ISO basis will be a useful document supported in general by Russian normative base but expanding a possible range of voluntary methods into well time-tested foreign approaches. This documents can be considered to be a toolkit annex to the Code of practice describing testing approaches beyond the scope of typical tasks

Stress Concentration Factors Calculation: Analytical and Numerical Approaches for Welded Tubular Joints

2020 ◽  
Author(s):  
Nathalia Paruolo ◽  
Thalita Mello ◽  
Paula Teixeira ◽  
Marco Pérez
Keyword(s):  
Stress Concentration ◽  
Oil And Gas ◽  
Hot Spot ◽  
Experimental Tests ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Gas Industry ◽  
Tubular Joints ◽  
Concentration Factors ◽  
Stress Concentration Factors

Abstract In the oil and gas industry, fixed platforms are commonly applied in shallow water production. In-place environmental conditions generates cyclic loads on the structure that might lead to structural degradation due to fatigue damage. Fatigue is one of the most common failure modes of offshore structures and is typically estimated when dimensioning of the structure during design phase. However, in times when life extension of existing offshore structures is being a topic in high demand by industry, mature fields may represent an interesting investment, especially for small companies. Concerning fixed platforms, composed mainly by welded tubular joints, the assessment of hot spot stresses is considered to predict structure fatigue. The estimation of welded joint hot spot stresses is based on the stress concentration factors (SCFs), which are given by parametric formulae, finite element analysis (FEA) or experimental tests. Parametric formulae may be defined as a fast and low-cost method, meanwhile finite elements analysis may be time consuming and experimental tests associated with higher costs. Given these different characteristics, each method is applied according to the study case, which will rely on the joint geometry and associated loads. Considering simple joint geometries several sets of parametric equations found in the literature may be applied. On the other hand, the SCFs calculation of non-studied yet complex joints consider known formulae adapted according to the under load joint behavior and geometry. Previous analysis shows that this adaptation may furnish different results compared to those obtained by FEA. Furthermore, it is observed that even for simple joints the results derived from the different methods may differ. Given their importance for the oil and gas industry, since they are the basis for the assessment of the fatigue life of welded tubular joints which may impact on additional costs related to maintenance and inspection campaigns, the estimation of SCFs must be the most accurate as possible. Therefore, this paper intends to investigate the differences between results derived from parametric formulae and different FEA studies.

New Generation of Heavy Wall Thicknesses Line Pipes for HPHT and Ultra-Deep Water Applications

2018 ◽  
Author(s):  
Stefano Crippa ◽  
Lorenzo Motta ◽  
Alessandro Paggi ◽  
Emanuele Paravicini Bagliani ◽  
Alessandro Elitropi ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Deep Water ◽  
Oil And Gas ◽  
High Pressures ◽  
Oil And Gas Industry ◽  
Rolling Process ◽  
Corrosion Properties ◽  
Line Pipe ◽  
Gas Industry ◽  
New Generation

Oil and Gas industry in the last decades has increased the use and need of heavy wall thickness line pipes, in particular for onshore / offshore high pressures and high temperatures (HP/HT) and offshore deep water / ultra-deep water applications. The paper presents the results achieved by Tenaris on seamless line pipes in grades X65/X70, according to API 5L / ISO 3183, with wall thickness in a range from 40 to 60 mm and diameter between 6 5/8” and 16”, produced by hot rolling process followed by quenching and tempering. Such line pipes are able to withstand very demanding conditions, like sour environment, very high pressure and wide temperature range. In this publication, the main outcomes of laboratory testing activities on the mentioned materials will be presented as part of heavy wall line pipe qualification. For this purpose, a special testing program, including mechanical and corrosion tests, has been executed. Material demonstrated an excellent behaviour, exhibiting both mechanical, toughness and stress corrosion properties suitable for the envisaged harsh applications.

Rationale for load specifications and load factors in the new CSA code for fixed offshore structures

1991 ◽  
Vol 18 (3) ◽  
pp. 454-464 ◽  
Author(s):  
Ian J. Jordaan ◽  
Marc A. Maes
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Limit States ◽  
Gas Industry ◽  
Offshore Installations ◽  
Load Factors ◽  
Annual Probability ◽  
Acceptable Risks ◽  
Economic Analyses

The Canadian Standards Association (CSA) initiated effort in 1984 aimed at the development of an offshore code for production structures in the oil and gas industry. The present paper summarizes the rationale behind the development of design load specifications in the preliminary standard S.471 "General requirements, design criteria, the environment, and loads." As part of this development, background calibration studies were conducted in tandem with the work of various committees. Selected results from these studies are also discussed in this paper. The basic objectives and tools for developing load criteria for the design of offshore installations are discussed. The use of economic analyses of cost versus safety of structures does not provide clear guidance, and the perspective taken is that of acceptable risks to an individual. This is used in the context of limit states design, which, in S.471, incorporates two safety classes. In order to provide consistent safety levels, the environmental loads are divided into categories based on frequent and rare occurrence, examples being waves and earthquakes, respectively. The role of the annual probability of failure in setting target levels of reliability as well as in the calibration process is emphasized. Various aspects of calibration are summarized, including the background to the rare-frequent separation of loads, the objective function used to optimize the results, as well as the method of handling model uncertainty. Key words: environment, limit states, loads, offshore, reliability, resistance, safety, structures.

ISO Offshore Structures Standards

2011 ◽  
Author(s):  
Philip Smedley ◽  
Pat O’Connor ◽  
Richard Snell
Keyword(s):  
Oil And Gas ◽  
Steel Structures ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
National Standards ◽  
Gas Industry ◽  
Technical Content ◽  
Technical Advances ◽  
Integrity Management ◽  
Specific Assessment

The ISO 19900 series of Standards address the design, construction, transportation, installation, integrity management and assessment of offshore structures. Offshore structural types covered by ISO include: bottom-founded ‘fixed’ steel structures; fixed concrete structures; floating structures such as monohull FPSOs, semi-submersibles and spar platforms; arctic structures; and site-specific assessment of jack-up platforms. All the fundamental ISO Offshore Structural Standards have now been published representing a major achievement for the Oil and Gas Industry and representative National Standards Organizations. A summary of the background to achieving this milestone is presented in this paper. In parallel, other Codes and Standards bodies such as API, CEN, CSA, Norsok and the Classification Societies are looking to harmonize some, or all, of their Offshore Structures Standards in-line with ISO, wherever this is desirable and practical. API, in particular, have been pro-active in reviewing and revising their Offshore Recommended Practices (RPs) to maximize consistency with ISO, including revising the scope and content of a number of existing API RPs, adopting ISO language, and embracing technical content. Given API’s long heritage of Offshore Standards it is not surprising that this remains very much a mutual effort between ISO and API with much in ISO Standards building on existing API design practice. Now published, those involved in developing and maintaining the ISO 19900 series of Standards have to deal with both new and existing challenges, including encouraging wider awareness and adoption of these Standards, enhancing the harmonization effort, ensuring technical advances are captured in timely revisions to these Standards, and most pressing to ensure that the next generation of offshore engineers are encouraged to participate in the long-term development of the Standards that they will be using and questioning. This paper is one of a series of papers at this OMAE Conference that outline the technical content and future strategy of the ISO Offshore Structures Standards.

Stress and Strain Fields in the Hemispherical Head of an FCC Regenerator During the Lifting Maneuver in Cyclone Replacement

2013 ◽  
Author(s):  
Erik Garrido ◽  
Euro Casanova
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Element Model ◽  
Sensitivity Analyses ◽  
Mechanical Equipment ◽  
Displacement Fields ◽  
Gas Industry ◽  
Total Displacement ◽  
Stress And Displacement Fields ◽  
Special Studies

The Oil and Gas industry is constantly seeking for improvements in the design of mechanical equipment. Each refining process is the subject of continuous research, which is frequently addressed in the revisions of the corresponding standard. Nevertheless, particular technologies such as the Fluid Catalytic Cracking Units (FCCU) are not governed by any International Standard but by designs developed and patented by specialized licensors. The implementation of new designs requires special studies of the original equipment in order to assess the feasibility of the related works and the required provisions to accomplish the revamp. This work studies the stress and displacement fields occurring in the hemispherical head of an FCC regenerator during the lifting maneuver for a typical cyclone replacement. A parametric finite element model was developed and stress and total displacement charts are presented as a function of diameters and thicknesses of hemispherical heads commonly found in the industry. Sensitivity analyses are presented with respect to a variation of ±15% of the applied loads and the size of the plenum chamber. Therefore, the results shown in this work present a reference framework for the replacement of cyclones in FCC regenerators when removing their hemispherical heads.

Incorporating the Higher Harmonics in VIV Fatigue Predictions

2007 ◽  
Author(s):  
Vikas Jhingran ◽  
J. Kim Vandiver
Keyword(s):  
Fatigue Damage ◽  
Strain Energy ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Dynamic Strain ◽  
Higher Harmonics ◽  
Gas Industry ◽  
Ongoing Research ◽  
Fatigue Design ◽  
Vortex Induced Vibrations

Vortex-Induced Vibrations (VIV) are an important source of fatigue damage for risers in the Oil and Gas industry. Results from resent VIV experiments by Vandiver et al. [1] indicate significant dynamic strain energy at not only the Strouhal frequency, but also its harmonics. In certain regions of the pipe, these higher harmonics accounted for more that half of the measured RMS strain and increased fatigue damage by a factor exceeding twenty. However, the state-of-the-art in VIV prediction only accounts for the vibrations at the Strouhal frequency. Preliminary results from a second set of experiments, described in this paper, confirm the importance of the higher harmonics in fatigue life estimates of pipes. Further, the authors formulate an approach to incorporate the higher harmonics in VIV related fatigue design. Finally, the authors identify the estimation of the higher harmonics, in both location and magnitude, as an important area of ongoing research, the results of which will be required to implement this proposed method.

Behavior Evaluation of Subsea Jumpers Exposed to Current by Experiment and FEM

2018 ◽  
Author(s):  
Mohammad Mobasheramini ◽  
Luciene Alves ◽  
Antonio Carlos Fernandes ◽  
Gilberto Bruno Ellwanger
Keyword(s):  
Deep Water ◽  
Oil And Gas ◽  
New Technologies ◽  
Flow Direction ◽  
Experimental Tests ◽  
Oil And Gas Industry ◽  
Experimental Result ◽  
Gas Industry ◽  
Oil Companies ◽  
Offshore Production

The oil and gas industry is headed toward deep water in recent years. Oil companies are seeking new technologies to meet the challenges of deep-water oil exploration and in the near future, this will bring new discoveries. The most difficulty of exploring oil in this region is the depth where the equipment is installed and the production lines must be safe for such activities. Full understanding of the dynamics of the behavior of this equipment is vital to the success of offshore production and operation due to environmental problems that can occur in an accident and a large amount of economic and human resources involved. The phenomenon of the vortex induced vibration (VIV) is complex and involves an interaction between hydrodynamic forces and the response of the structure. The force and displacement can be determined through experimental tests or the complete numerical simulation of the interaction between the structure and fluid. DNV-GL has recently published a guideline about the design of a subsea jumper [1], but it is still needed many studies and experiments to improve the evaluation of VIV in rigid subsea jumpers in the oil industry. The main objective of the present work is to investigate VIV phenomenon in a jumper exposed to uniform flow and verify its oscillation in the flow direction, which called inline VIV (VIVx). Throughout this study, the finite element method was used to perform the structural and modal analysis of the structure, in order to obtain the modes, frequencies and then validate the experimental result. Experimental analysis of jumpers was also performed in a current tank to evaluate the behavior of the jumper with the current flow.

Guyana: Liza Phase 1 Rapid Development in a Deepwater Frontier

2021 ◽  
Author(s):  
Amy Styslinger ◽  
David Yost ◽  
Gina Dickerson ◽  
Antoine Minois ◽  
Renee Wiwel
Keyword(s):  
Deep Water ◽  
Oil And Gas ◽  
Rapid Development ◽  
Phase 1 ◽  
Oil Production ◽  
Oil And Gas Industry ◽  
Development Project ◽  
Gas Industry ◽  
Cycle Times ◽  
Water Developments

Abstract The Liza Phase 1 development project, offshore Guyana, is an unique example of what the offshore oil and gas industry is capable of when working together to deliver a common objective. ExxonMobil and the Stabroek Block co-venturers, Hess Guyana Exploration Limited and CNOOC Petroleum Guyana Limited, commenced oil production from the Liza Destiny floating production, storage, and offloading (FPSO) vessel in December of 2019, less than 5 years from the initial discovery of hydrocarbons in the Staebroek block. With the production and export of its first barrels of oil, the project completed the establishment of a nascent oil and gas industry in Guyana that is poised for tremendous growth in the coming years. The Liza Phase 1 development consists of a 120 kbd conversion FPSO (The Liza Destiny) and a network of subsea infrastructure to produce from and inject in two drill centers. It is expected to develop a resource of about 450 MBO gross estimated ultimate recovery. The water depth ranges from 1,690–1,860 m throughout the development which is located approximately 200 km offshore Guyana. This paper highlights the scope and pace of the project and discusses three specific challenges overcome: the uncertainty of the metocean conditions, extending the application of the selected riser technology, and executing in a challenging and frontier offshore location. A key to the success of the project was the unified approach between stakeholders and the commitment to act as One Team. The Liza Phase 1 project rapidly developed a newly discovered deep water resource in a frontier location while overcoming numerous challenges. By delivering Guyana's first ever oil production among industry leading cycle times, the Liza Phase 1 project has set the foundation for the future of deep water developments in Guyana.

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