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Steel catenary risers (SCR) have been a favored choice for recent ultra-deep waters field developments subjected to harsh environments and large floating production units (FPU) motions. The design of SCRs in such conditions is always a great challenge where the key issues are the fatigue near the hang-off and at the touch down point; clashing between lines, especially on fields with a large number of wells and high payloads on the production unit. This paper describes the solution provided by the Buoy Supporting Risers (BSR) concept which has recently been installed in the Santos basin offshore Brazil.Subsea7 detailed the original concept of BSR system, from the design to fabrication and installation. The BSR concept combines several benefits to overcome the challenges of installing SCRs on ultra-deep waters, such as: allowing decoupling between installation of risers/flowlines and the platform, reducing payload on the production unit, very small dynamics transmitted from production unit to the risers, resulting in significant less fatigue issues. Also, the BSR concept reduces the risks associated with clashing and interference due to the smaller dynamics when compared to traditional coupled solutions. Fabrication is also addressed to highlight main challenges associated to assembling and welding clad and lined pipelines.In this paper the key aspects of the design and qualification are presented. Due to sour and CO2 service requirements for the production and water injection risers, it was decided to use corrosion resistant alloy (CRA) mechanically lined pipe for the entire line, with the exception of the top and touch down sections, where metallurgical clad pipe was used. Considering its novelty, a significant amount of qualification and testing was demanded. Among the technological innovations part of the SCR package is the first successful application of a pressurized mechanically lined pipe by reel-lay method. The solution involved an extensive qualification program, including full scale tests on vessel. The methodology and rationale to allow the application of high strain levels during spooling mitigating potential risk of wrinkling within the internal liner, had to be addressed during the detailed design by extensive Finite Element Analysis and validation tests.The SCR itself, due to de-coupling of motions by the buoy, have negligible dynamic response from vessel motions, thereby behaving almost like a static system with robust fatigue performance. The only meaningful fatigue in SCRs is due to current induced VIV and is mitigated using strakes. There was negligible potential clashing with adjacent SCRs.This paper provides a summary of design and qualification work carried for SCRs lined pipes installed in the BSR system and a discussion regarding main outcomes.

RESUMO Este trabalho apresenta um procedimento de avaliação para a determinação da J Integral e do CTOD para dutos com trincas circunferenciais em sua superfície externa e interna submetidos à flexão pura para uma ampla faixa de geometrias de trinca e propriedades (encruamento) de material baseados em soluções das componentes plásticas de J e CTOD. Uma descrição da metodologia sobre a qual J e CTOD são determinados estabelece o contexto necessário para a determinação das funções adimensionais 1 h e 2 h aplicáveis a uma grande faixa de geometrias de trinca e propriedades de material características de aços estruturais para a construção de dutos e vasos de pressão. As extensivas análises numéricas não-lineares 3-D fornecem um conjunto completo de soluções para J e CTOD , os quais entram diretamente em procedimentos avançados para a avaliação de defeitos em dutos e cilindros submetidos à flexão. Este estudo também examina uma comparação exploratória entre os resultados do procedimento proposto e os resultados de análises numéricas por elementos finitos de dutos com trincas superficiais submetidos ao processo de enrolamento. ABSTRACT This work provides an estimation procedure to determine the J-integral and CTOD for pipes with circumferential surface cracks subjected to bending load for a wide range of crack geometries and material (hardening) based upon fully-plastic solutions. A summary of the methodology upon which J and CTOD are derived sets the necessary framework to determine nondimensional functions 1 h and 2 h applicable to a wide range of crack geometries and material properties characteristic of structural, pressure vessel and pipeline steels. The extensive nonlinear, 3-D numerical analyses provide a definite full set of solutions for J and CTOD which enters directly into fitness-for service (FFS) analyses and defect assessment procedures of cracked pipes and cylinders subjected to bending load. The study also examines an exploratory comparison between the resulting fully-plastic solutions and finite element analyses of circumferentially cracked pipes subjected to reeling. I Constante de integração da singularidade HRR J J Integral 2 J Teoria de plasticidade de Von Mises c J Valor crítico da J Integral e J Componente elástica da J Integral p J Componente plástica da J Integral p J Valor normalizado de p J pred J Valor previsto de J reel J Valor numérico máximo J atingido na simulação do processo de enrolamento I K Fator de intensidade de tensões Ic K Valor crítico do fator de intensidade de tensões LLD Deslocamento da linha de carga M Momento fletor aplicado 0 kJ J pred pred reel J J 0,1

This study examines the applicability of a stress-based criterion based upon plastic instability analysis to predict the failure pressure of corroded pipelines with axial defects. A central focus is to gain additional insight into effects of defect geometry and material properties on the attainment of a local limit load to support the development of stress-based burst strength criteria. A verification study conducted on burst testing of large-diameter pipe specimens with different defect length shows the effectiveness of a stress-based criterion using local ligament instability in burst pressure predictions, even though the adopted burst criterion exhibits a potential dependence on defect geometry and possibly on material’s strain hardening capacity. Overall, the results presented here suggests that use of stress-based criteria based upon plastic instability analysis of the defect ligament is a valid engineering tool for integrity assessments of pipelines with axial corroded defects.