Reel-lay Method Research Articles

Theoretical and experimental study on the change of mechanical properties of pipelines before and after reel-laying

During the reeling process of the reel-lay method, the pipeline undergoes multiple bending deformations, resulting in multiple plastic deformations, which affects the mechanical properties of pipeline materials. This paper innovatively describes the calculation method of the overall stress of the pipe after reel-laying based on elastoplastic self-reinforcing theory and bilinear strengthened constitutive model, and clarifies the influence of plastic deformation of reel-laying on the performance strengthening of pipe. Through the comparative test of the mechanical properties of the pipe before and after reel-laying, the accuracy of the theoretical results is verified. The results show that there will be residual strain in the pipe after reel-laying. Plastic deformation will improve the performance of the pipe material, the tensile, compression, bending and torsion resistance of the pipe are strengthened after reel-laying. Theoretically, the maximum potential increase is 45.16%, and experimental measurements have shown conformity to theoretical values.

Multi-scale coupling numerical modeling of metallic strip flexible pipe during reel-lay process

Complex plastic deformation and local buckling may occur due to the nonlinear contact between the pipe and drum in the offshore pipeline laying by reel-lay method. In this paper, material performance tests are carried out to obtain the nonlinear stress-strain constitutive models for high density polyethylene (HDPE) material and steel strip. Meanwhile, full-scale tensile tests are also conducted to acquire the tension-strain correlation of metallic strip flexible pipe (MSFP). Then, shell element and solid element are combined to establish an ABAQUS multi-scale finite element model (FEM) for MSFP under the coiled laying condition. The proposed multi-scale FEM consists of three components, i.e. two simplified components and one fine component, which could accurately and efficiently simulate the mechanical properties of flexible pipe under the coiled laying condition. The results indicate that: due to the radial extrusion restriction of spiral steel strips, the Mises stress distribution of inner HDPE layer shows a more uniform spiral strip distribution than outer HDPE layer; the most dangerous condition for MSFP may be when it is just partially wound up on the drum; the effect of friction coefficient on the spiral steel strips seems obviously larger than the effects of traction force and drum diameter.

Concurrent 10. Presentation for: Collaborating to bring new technology on developments

Presented on Wednesday 18 May: Session 10 Project delivery certainty is a key a success factor for positive business outcomes. Taking on world first applications across multiple delivery streams comes with risk that requires significant risk reduction to meeting business requirements. The Julimar Development completed this successfully across both drilling and completions, and subsea. Reliable multizone completions with robust sand control have traditionally been a challenge in high-rate gas wells. Cased hole stacked gravel packs can leave high mechanical skin, require multiple trips and are complex operations. While Open Hole Gravel Packs (OHGPs) have provided reliable sand control in such wells, multizone applications have been limited due to the tradeoff between effective gravel placement and zonal isolation. Recent developments in technology have enabled reliable gravel placement and complete zonal isolation. The collaboration between Woodside and Subsea 7 has delivered an ‘industry first’ on the Julimar Project, with the completion of an 18″ Corrosion-Resistant Alloy (CRA) gas transmission flowline installed via reel-lay – the largest diameter insulated CRA pipeline ever reeled. For background, most projects have traditionally used the ‘S-Lay’ method for installing pipe in Australia – the reel-lay method is less common. A key benefit of the reel-lay method is it removes thousands of welds from the offshore installation vessel critical path, transferring them onshore into a safer, quality-controlled environment earlier in the schedule. Pipe joints are welded into ‘stalks’ which are then spooled onto purpose-built reel-lay vessels. Woodside and Subsea 7 were able to jointly demonstrate the safety, quality, technical and cost advantages of this innovative but field-proven reeled pipe-lay technology. The 18″ CRA flowline is a tangible example of the performance that can be delivered through early collaborative engagement and strategic investment in technology and is a step change in Australia and the industry. This joint presentation discusses contracting, design, execution and evaluation of technologies on the Julimar Development. It includes the method followed for reel-lay technology selection, engineering development, post project evaluation and the health and safety benefits. The presentation provides both the Operator and Contractor perspectives on the challenges of implementing new technology in developments in Australia. To access the presentation click the link on the right. To read the full paper click here and also here.

Collaborating to bring new technology on developments

Project delivery certainty is a key a success factor for positive business outcomes. Taking on world first applications across multiple delivery streams comes with risk that requires significant risk reduction to meeting business requirements. The Julimar Development completed this successfully across both drilling and completions, and subsea. Reliable multizone completions with robust sand control have traditionally been a challenge in high-rate gas wells. Cased hole stacked gravel packs can leave high mechanical skin, require multiple trips and are complex operations. While Open Hole Gravel Packs (OHGPs) have provided reliable sand control in such wells, multizone applications have been limited due to the tradeoff between effective gravel placement and zonal isolation. Recent developments in technology have enabled reliable gravel placement and complete zonal isolation. The collaboration between Woodside and Subsea 7 has delivered an ‘industry first’ on the Julimar Project, with the completion of an 18″ Corrosion-Resistant Alloy (CRA) gas transmission flowline installed via reel-lay – the largest diameter insulated CRA pipeline ever reeled. For background, most projects have traditionally used the ‘S-Lay’ method for installing pipe in Australia – the reel-lay method is less common. A key benefit of the reel-lay method is it removes thousands of welds from the offshore installation vessel critical path, transferring them onshore into a safer, quality-controlled environment earlier in the schedule. Pipe joints are welded into ‘stalks’ which are then spooled onto purpose-built reel-lay vessels. Woodside and Subsea 7 were able to jointly demonstrate the safety, quality, technical and cost advantages of this innovative but field-proven reeled pipe-lay technology. The 18″ CRA flowline is a tangible example of the performance that can be delivered through early collaborative engagement and strategic investment in technology and is a step change in Australia and the industry. This joint presentation discusses contracting, design, execution and evaluation of technologies on the Julimar Development. It includes the method followed for reel-lay technology selection, engineering development, post project evaluation and the health and safety benefits. The presentation provides both the Operator and Contractor perspectives on the challenges of implementing new technology in developments in Australia.

Numerical Simulations and Experimental Study on the Reeling Process of Submarine Pipeline by R-Lay Method

During the reeling process of the reel-lay method, the pipe will be subjected to combined loading of tension and bending. Excessive ovalization of the pipe will affect the structural performance and even lead to structural instability of the pipe. In this paper, a numerical simulation model of the pipe-reeling process is established by finite element tools. The Ramberg–Osgood material model is used to study the ovalization and bending moment of the pipe cross-section during the pipe-reeling process based on the Von Mises plasticity and nonlinear kinematic hardening rules. The results show that the ovalization and bending moment of the pipe section will change significantly during the pipe-reeling process. Subsequently, one set of 6-inch pipe-reeling experimental setups was designed to conduct a full-scale experiment. Compared with the experimental results, the feasibility of the finite element model is verified. Finally, the effects of diameter-to-thickness ratio, the material parameters of the pipe, and the pipe axial tension on the ovalization and bending moment changes are studied. Research shows that each parameter has a certain influence on the pipe of the reeling process, and the diameter-to-thickness ratio of the pipe has the most obvious effect. When the diameter-to-thickness ratio decreases, the bearing capacity for bending moments and the ability to resist ovalization of pipe are enhanced. At the same time, each parameter has a significant impact on the reeling process of the pipeline.

Effects of full-scale reel-lay simulation on mechanical properties of X65 grade pipeline girth welds

The reel-lay method is one of the most effective procedures for installing submarine pipelines. During the reel-lay installation process, pipelines are subjected to large-scale plastic strain because of cyclic bending/straightening processes. Thus, mechanical tests must be carried out to assess the effect of large-scale pre-strain on the girth weld of pipelines after cyclic bending/straightening processes. Tensile tests were performed on weld metals, the results showed that a slight increase in tensile and yield strength were caused by a pre-strain of 2.709 % (maximum strain region). A single-edged notched tension (SENT) specimen was examined via the unloading compliance method to evaluate the fracture toughness for the base metal, weld metal and HAZ. The fracture toughness test results showed that the weld metal exhibited the lowest fracture toughness followed by the base metal and HAZ. The fracture toughness of the base metal, the weld metal and HAZ all decreased after the cyclic bending/straightening with a pre-strain of 2.709 %.

Safety assessment study of a planned offshore floating platform pipelaying test

ABSTRACTServing as the most important component of a subsea production system, marine risers are one of the weakest and vulnerable marine structures. Therefore, the offshore pipelaying installation operation has been drawing more and more attention. In this paper, a safety assessment study of a planned offshore floating platform pipelaying test by reel-lay method is put forward. First, the real marine environment data and platform motion are collected in the field from the sea area. Then, tensile and bending tests of a flexible pipe are conducted to acquire its nonlinear tension-strain and moment-curvature mechanical properties. Later, based on the improved rod theory, the analyses of the flexible pipe's motion response under the offshore pipelaying operation are carried out by fully taking account of the irregular platform motion and hydrodynamic loadings caused by wave and current. Finally, a methodology for the flexible pipe offshore laying operation could be established.

Development of a strain based fracture assessment procedure for undermatched pipe girth welds subjected to bending

Structural integrity assessment of pipeline girth welds subjected to high strain levels which arises from the reel-lay method relies on precise crack driving force estimation procedures. Recent developments in subsea technology favor the use of high strength carbon steel pipelines with an internal corrosion resistant layer to increase protection against corrosive fluids. In contrast to homogeneous structural components, the bimetal configuration may induce the occurrence of weld strength undermatch, with a strong impact on the relationship between remote applied load and crack tip constraint. This work explores the development of a crack driving force estimation procedure based on a strain-based version of the EPRI J estimation scheme coupled with the equivalent stress-strain relationship method (ESSRM) and a weld geometry simplification procedure. The proposed framework takes advantage of the displacement controlled nature of the reeling process. Extensive 3D analyses provide a large set of fracture parameters applicable to the strain-based EPRI methodology followed by parametric analyses conducted to assess the accuracy of the new procedure. Subsequently, a case study is performed to determine the tolerable crack sizes in an idealized pipe installation. The procedure shows an overall good agreement to the benchmark analyses and increased accuracy when compared to the recommended approach proposed by DNV.

New tool for internal pressure during fabrication and installation of mechanically lined pipelines using reel-lay method

As an ideal use of corrosion-resistant alloys and low-alloy steels, Mechanically Lined Pipelines (MLPs) have been employed gradually for offshore exploitation. If the risk of thin-walled liner wrinkling is to be effectively averted, reel-lay is the most economical installation method for this type of pipeline, especially for deepwater oil and gas development. A suite of tools and corresponding techniques is proposed in this paper to realize the spooling-on of an MLP stalk with inner pressure to avoid detachment and wrinkling of the MLP liner. Additionally, The related numerical verification and a prototype test for a 5-in. MLP spooling-on tool are completed to prove the validity of this new technique and further illustrate the application effect of providing internal pressure during the spooling-on of MLP stalk to a reel.

Fully-Plastic Strain-Based J Estimation Scheme for Circumferential Surface Cracks in Pipes Subjected to Reeling

Modern installation techniques for marine pipelines and subsea risers are often based on the reel-lay method, which introduces significant (plastic) strains on the pipe during reeling and unreeling. The safe assessment of cracklike flaws under such conditions requires accurate estimations of the elastic–plastic crack driving forces, ideally expressed in a strain-based formulation to better account for the displacement controlled nature of the reeling method. This paper aims to facilitate such assessments by presenting a strain-based expression of the well-known Electric Power Research Institute (EPRI) estimation scheme for the J integral, which is directly based upon fully plastic descriptions of fracture behavior under significant plasticity. Parametric finite element simulations of bending of circumferentially cracked pipes have been conducted for a set of crack geometries, pipe dimensions, and material hardening properties representative of current applications. These provide the numerical assessment of the crack driving force upon which the nondimensional factors of the EPRI methodology, which scale J with applied strain, are derived. Finally, these factors are presented in convenient graphical and tabular forms, thus allowing the direct and accurate assessment of the J integral for circumferentially cracked pipes subjected to reeling. Further results show that crack driving force values estimated using the proposed methodology and the given g1 factors are in very close agreement to those obtained directly from the finite element simulations.

Multiaxial fatigue analysis on reeled deepwater steel catenary risers with girth weld defects

In the present study, we simulated the reel-lay installation process of deepwater steel catenary risers (SCRs) using the finite element method and proposed multiaxial fatigue analysis for reeled SCRs. The reel-lay method is one of the most efficient and economical pipeline installation methods. However, material properties of reeled risers may change, especially in the weld zone, which can affect the fatigue performance. Applying finite element analysis (FEA), we simulated an installation load history through the reel, aligner, and straightener and analyzed the property variations. The impact of weld defects during the installation process, lack of penetration and lack of fusion, was also discussed. Based on the FEA results, we used the Brown-Miller criterion combined with the critical plane approach to predict the fatigue life of reeled and non-reeled models. The results indicated that a weld defect has a significant influence on the material properties of a riser, and the reel-lay method can significantly reduce the fatigue life of SCRs. The analysis conclusion can help designers understand the mechanical performance of welds during reel-lay installation.

Analysis of flexural behaviour of reinforced thermoplastic pipes considering material nonlinearity

Reinforced thermoplastic pipes (RTPs) are considered as prospective alternatives to traditional steel pipes in different offshore oil and gas applications due to their attractive properties. The spoolable versions of these pipes can be efficiently installed by the reel-lay method with relative ease. Nonlinear flexural behaviour of RTPs composed of a liner made of pipe grade polyethylene (PE), aramid fibre reinforced PE layers and a PE outer cover is modelled and analysed using finite-element analysis (FEA) considering the material nonlinearity. The pipe is modelled as a cylindrical shell in Abaqus/Standard. Numerical algorithms reflecting strain-dependent mechanical characteristics of PE are employed to perform simulations. Advantages of the proposed modelling approach are demonstrated with numerical examples. The minimum allowable bend radii of RTPs with different ply angles are determined. The effects of diameter-to-thickness ratios and the material nonlinearity on the spoolability of RTPs have been investigated. It is shown that the spoolability of RTPs can be improved by employing a certain two angle-ply reinforcing layer system, which could reduce the installation costs.

Fractographic Analysis of Weld Metal and HAZ Regions of API X-80 Steel Subjected to Simulation of the Reel-Lay Method

The reel-lay method is a process commonly used for rigid riser installation. During this process, riser materials are subjected to high strain levels and associated plastic damage which can affect their structural integrity. The aim of this work was to evaluate the fracture surfaces at weld metal and heat-affected zone regions of API X-80 steel three-point bend specimens, SE(B), subjected to reel-lay method simulations. The pre-existence of circumferential planar defects at 12 o’clock position was considered and the J-integral was used to simulate the reel-lay condition at the defects. Different strain levels considering conditions less and more severe than the real one were also studied. The results showed a great influence of J magnitude on fracture surface morphology. The increase of J magnitude led to a greater local surface damage on the specimens and stable crack growth during reel-lay simulation. High loading conditions should be avoided in the operation in order to prevent further structural damage of the materials.

Multiaxial Fatigue Analysis on Reeled Steel Tube Umbilical

Multiaxial fatigue analysis on reeled steel tube umbilical is proposed based on finite element analysis (FEA) results. Due to the complexity of the umbilical geometry, the stresses and strains field becomes multiaxial, worsening the fatigue resistance. The reel-lay method is one of the most efficient and cost-effective methods of umbilical installation. However, if installed by the reel-lay method, material properties of the umbilical change may have an influence in fatigue performance of the line. Finite element analysis is applied with contact formulation, and the load history through the reel, aligner, and straightener is simulated. The strain history of the whole modeling process in the critical element is given, and the properties' change after the load history is discussed. Then, the principal stress criterion and the Brown–Miller criterion (both combined with the critical plane approach) based on FEA results are used to do fatigue life prediction of reeled and nonreeled models. The results indicated that a reel-lay method has a great influence on the fatigue life of steel tube umbilical, so the influence of installation on the steel tube umbilical fatigue must be considered when the reel-lay method is adopted.

The Effect of Prestrain on Ductile Fracture Toughness of Reeled Pipeline Steels

The reel-lay method is a cost efficient alternative to the S-lay and J-lay methods for small to medium size steel offshore pipelines. The quality of the pipeline construction is enhanced by on-shore welding and inspection under controlled conditions. However, reeled pipelines are subjected to at least two symmetrical plastic strain cycles during installation. The plastic straining associated with reeled installation modifies the axial tensile response of the pipe material. Also, it has been suggested that plastic straining may reduce fracture toughness. In this work, small scale tests representative of conditions experienced under reeling of steel pipelines have been carried out. The fracture resistance curves obtained for the material in the as-received and strained conditions have been compared. No significant effect of the reeling strain cycle on the fracture toughness during subsequent straining was observed.

Technology Focus: Offshore Facilities (February 2011)

Technology Focus Our industry continues to make great progress in creating and qualifying new technical solutions to meet the need for cost-effective offshore oil-/gas-production facilities in evermore-challenging environments. In last year’s Offshore Facilities Focus, we reviewed some of the more-prominent recent examples, and in this edition we cover some further updates on progress. There is, however, a particular theme running through these latest examples, which are perhaps worthy of some special attention. The E&P industry is renowned for its ability to generate impressive technical solutions for just about any well-defined offshore challenge it may face. In my experience, it has been less able to demonstrate a similar global consistency across cultures in the manner in which the supplier and the client go about achieving the potential of the technology in practice. In one recent firsthand exposure, there even appeared to be a deliberate mind-set of challenge and contractual standoff from the outset between the two parties. The intended aim was to bring about rapid execution at lowest possible cost. It is questionable whether this approach ever can be sustainable beyond the particular project in question, and whether either party’s best interests can thereby be served in practice. What shines through in the examples covered in the following pages is how a purposefully collaborative approach can make a positive difference to the benefits for both parties. These benefits often can be enhanced further by establishing a broader constructive and collaborative framework with a wider group of stakeholders that typically can include installation contractors and classification/certification agencies. The success of individual-project collaborations leads to a sustainable contracting environment into the future. Also, it can, in some cases, lead to global frame agreements, which can enable both parties to harvest expanded economic and schedule benefits from building on the culture of mutual respect and aligned objectives. I hope you enjoy these case studies as much as I have. Offshore Facilities additional reading available at OnePetro: www.onepetro.org. OTC 20762 “Demonstrating the Feasibility of Steel Catenary Risers From a Cylindrical FPSO in Harsh Deepwater Locations” by Jan V. Aarsnes, Sevan Marine ASA, et al. OTC 20506 “Deepwater-Pipeline and -Riser Installation by the Reel-Lay Method” by S.N. Smith, Subsea 7, et al. OTC 21024 “Top-Tensioned-Riser Systems for a New Floater Type” by David L. Garrett, Stress Engineering Services, et al.