Practical Aspects of Cost-Effective Solution for Global Lateral Buckling Mitigation with Residual Curvature Method for Subsea Pipelines

Lateral Buckling Mitigation of Subsea Pipeline by Temporary Winch Pull

10.1115/omae2021-62362 ◽

2021 ◽

Author(s):

Yann Le Maout ◽

Michele Ceruli

Keyword(s):

Cost Effective ◽

Engineering Process ◽

Lateral Buckling ◽

Reliability Design ◽

Limited Impact ◽

Design Concepts ◽

Wide Range ◽

Effective Option ◽

Residual Curvature ◽

Subsea Pipelines

Abstract The design process of lateral buckling has gained in maturity over the last ten years. However the design of any required engineered trigger to control the formation of lateral buckles remains open to a wide range of design concepts (like sleeper, buoyancy modules, snake lay or residual curvature method) with sometimes increasing complexity in either engineering, fabrication or installation. This paper will describe how a lateral deflection initiated by a temporary subsea winch after pipelay can be used as a reliable mitigation with limited impact on the project execution. The interaction between the winch pull and the pipe soil interaction and the consequences on both the post buckle behaviour and reliability design of the mitigation architecture will be presented. The advantages of this technique (decoupling of construction activities between pipelay and lateral buckling mitigation, standard engineering process, no offset from seabed, no additional permanent equipment) and its limitations (stiff pipeline, detailed pipe soil interaction) will be discussed. The operational feedback from several flowlines designed, installed and operated with this winch pull mitigation will be reviewed and the main lessons learnt will be highlighted. It can be concluded that this temporary subsea winch pull is an interesting and cost effective option for lateral buckling initiation of subsea pipelines.

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Lateral Buckling Mitigation in Deep Waters - A Total Installed Costs Comparison

10.4043/30969-ms ◽

2021 ◽

Author(s):

Hemant Priyadarshi ◽

Matthew Fudge ◽

Mark Brunner ◽

Seban Jose ◽

Charlie Weakly

Keyword(s):

Shallow Water ◽

Deep Water ◽

Cost Effective ◽

Cost Comparison ◽

Lateral Buckling ◽

Track Record ◽

Deep Waters ◽

Residual Curvature ◽

Mitigation Techniques ◽

Mitigation Methods

Abstract The paper introduces lateral buckling mitigation techniques (sleepers, distributed buoyancy sections, and residual curvature method or RCM) used in deep water fields and provides a total installed cost comparison of these solutions in relative terms. A hypothetical deep-water scenario is used to compare all techniques within the same site environment. Historic benchmarks have been used to make a relative comparison of these buckle mitigation methods on the engineering, procurement, fabrication, and installation fronts. In addition, risks associated with engineering, procurement/fab and installation have been listed to illustrate the risks versus rewards tradeoff. While sleepers and distributed buoyancy have been previously used in deep water, RCM doesn't have a significant track record yet. RCM is a proven and cost-effective buckle mitigation solution in shallow water. This paper compares its application in deep water to the prevailing buckle mitigation methods and confirms if it creates value (savings and reduces risks) for an offshore installation project. It is assumed that each mitigation method is appropriate for the hypothetical deep-water scenario.

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Validation of Residual Curvature Installation for Lateral Buckling Management Using Structural Reliability Analysis (SRA)

Volume 5B: Pipelines, Risers, and Subsea Systems ◽

10.1115/omae2017-61541 ◽

2017 ◽

Author(s):

Martin Teigen ◽

Malik M. Ibrahim

Keyword(s):

Finite Element ◽

Reliability Analysis ◽

Structural Reliability ◽

Control Method ◽

Multivariate Interpolation ◽

Design Parameters ◽

Bending Moments ◽

Lateral Buckling ◽

Residual Curvature ◽

Subsea Pipelines

The method of using residual curvature during pipeline installation, primarily for the purpose of lateral buckling control, has caught an increasing amount of attention over the past few years [1], [9]. The use of residual curvature sparked a particular interest after positive experiences from a 26 km long pipeline on Statoil’s Skuld project (2012) in the Norwegian Sea [7]. As such, a range of technical papers elaborating on the topic have recently been published [6], [7], [9]. Some of this work has identified some particularly novel applications for the residual curvature method including freespan mitigation to reduce the requirement for seabed intervention, allowing for direct pipeline tie-ins, use with s-lay installation and even for steel catenary risers [10], [11]. However, these applications are currently only identified and not yet proven successful in any published work. This technical paper focusses on validating the use of residual curvature for the purpose of lateral buckling control in subsea pipelines installed by reel-lay. The residual curvature method demonstrates high buckling reliability without the use of subsea structures or additional installation equipment, with a controlled buckle response and favourable operational bending moments [1]. The residual curvature method has been shown less sensitive to some design parameters than other lateral buckling control methods [6]. However, published work also show that high strains will develop for short residual curvature lengths, high pipe-seabed frictions and for certain levels of residual strains [6]. Previous research has predicted the behaviour of residual curvature as a means of controlling lateral buckling in a deterministic approach [6], [7], [9]. However, performing a lateral buckling design with a probabilistic approach can offer a more realistic design and demonstrate higher reliability. There is a range of research on probabilistic approaches for lateral buckling design of subsea pipelines, but there is little published work on the same approach for residual curvature in particular. For this reason, this paper suggests a method for determining the likelihood of buckling and the associated bending moments via structural reliability analysis (SRA). A numerical model combining Finite Element (FE) Analysis and a Monte Carlo simulation is applied. A similar approach has already been presented by others for a different lateral buckling control method, and involves forming a database of finite element solutions followed by multivariate interpolation for the stochastic variables [16]. The multivariate interpolation necessitates a permutation of the cases in an FE result database. In order to keep the simulation efficient, only a limited number of variables are treated as stochastic. The variables that are considered as stochastic are those that have been determined that the lateral buckling response due to residual curvature is sensitive to. The variations of the remaining parameters are also accounted for but in a simpler way. The suggested SRA is used to assess the reliability of a pipeline that resembles the Skuld pipeline. The proposed SRA validates that residual curvature is a reliable lateral buckling control method irrespective of great variations in the design parameters that cannot be quantified easily, such as target residual strain. The proposed SRA also serves as a cost attractive solution in the qualification testing, by potentially relieving the installation contractor from the expensive exercise of performing an additional straightening trial.

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