Improvement of Fatigue Life of Steel Catenary Risers and Oil Offloading Lines in West Africa

2008 ◽  
Author(s):  
Daniel Bertaso ◽  
Graham Hutt ◽  
Jue Wang ◽  
Paul Tews
Keyword(s):  
Fatigue Life ◽  
West Africa ◽  
Steel Catenary Risers

Improving the Fatigue Performance of Welded Tubular Connections via Flared and Thickened Pipe Ends

2021 ◽  
Author(s):  
Ghiath Guy Mansour
Keyword(s):  
Fatigue Life ◽  
Lower Cost ◽  
Fatigue Performance ◽  
Viable Alternative ◽  
Welding Time ◽  
Time Cost ◽  
Steel Catenary Risers ◽  
The Many ◽  
Espirito Santo

Abstract Fatigue is a primary challenge in the design of steel catenary risers (SCRs) and different measures and methods are utilized to mitigate it. Traditional upset ends and steel lazy wave risers (SLWRs) are such methods to mitigate fatigue. SLWRs were first used in 2009 on the Espirito Santo floating, production, storage, and offloading (FPSO) vessel of Shell Company's Parque das Conchas (BC-10) project offshore Brazil. SLWRs have been used increasingly since then and gained popularity especially in recent years. A novel patented tubular connection assembly referred to as Flared Thickened Ends (FTEs) improves the fatigue life of SCRs and welded connections in general. This novel assembly has many advantages. It overcomes the thickness limitation of welding traditional upset ends and reduces offshore welding time, cost, and risk. When FTEs are used in simple SCRs, they render simple SCRs a robustly viable alternative at significantly lower cost, shorter schedule, and with many additional advantages as compared to SLWRs. Of the many advantages, simple SCRs are more straightforward to configure, analyze, design, and install using varied installation methods and vessels. Simple SCRs use less materials and offer better long-term integrity, especially for insulated SCRs. In addition, they have a smaller footprint and are less prone to clashing than SLWRs.

Impact of Soil Modeling on Fatigue Design of Lazy Wave Riser Systems

2019 ◽  
Author(s):  
Rupak Ghosh ◽  
Haydar Arslan
Keyword(s):  
Fatigue Life ◽  
Water Injection ◽  
Field Testing ◽  
Vertical Displacement ◽  
Soil Response ◽  
Fatigue Design ◽  
Steel Catenary Risers ◽  
Design Requirements ◽  
Seabed Stiffness

Abstract The Liza risers comprise production risers, water injection risers and gas injection risers, and a lazy wave configuration is selected considering FPSO motion, reservoir fluid and overall project execution requirements. During operation, the risers are expected to move cyclically with small vertical displacement amplitudes (e.g. 0.1% to 1% of the riser diameter), and a key design issue is the fatigue life of these risers at critical locations including the touch-down zone which will be governed by the seabed stiffness. The role of soil response on fatigue life of riser with buoyancy has been investigated through nonlinear finite element and comprehensive lab and field testing program. Published methodologies for determining seabed stiffness values for risers concentrate more on larger amplitude motions based on the design requirements of steel catenary risers. The paper presents the sensitivity of the fatigue life at TDP to various soil model and provides insight in the results. Also included is the importance of site specific soil investigation in the context of design of riser.

Fatigue Life Analysis for a Steel Catenary Riser in Ultra-Deep Waters

2012 ◽  
Author(s):  
Marcos V. Rodrigues ◽  
Caroline Ferraz ◽  
Danilo Machado L. da Silva ◽  
Bruna Nabuco
Keyword(s):  
Fatigue Life ◽  
Global Analysis ◽  
Fatigue Behavior ◽  
Density Variation ◽  
Steel Catenary Riser ◽  
Deep Waters ◽  
Internal Fluid ◽  
Steel Catenary Risers ◽  
Fatigue Life Analysis ◽  
Definition Of

With new discoveries in the Brazilian Pre-Salt area, the oil industry is facing huge challenges for exploration in ultra-deep waters. The riser system, to be used for the oil transportation from seabed to the production unit, is one of them. The definition of riser configurations for ultra-deep waters is a real challenge. Problems have being identified for flexible risers, hybrid risers and steel catenary risers (SCR) configurations to comply with rules requirements and criteria in water depths of 2000m. The objective of this work is to present a study on the fatigue behavior of a Steel Catenary Riser in 1800m of water depth. One of the main challenges for SCRs in ultra-deep waters is the fatigue, due to platform 1st order motions, at the touch down zone (TDZ). A case study is presented for a Steel Catenary Riser connected to a semi-submersible platform. The influence of some design and analysis parameters is studied in order to evaluate their impact on the SCR fatigue life. The main parameters to be evaluated in this work are: The mesh refinement, in the global analysis, at the Touch Down Zone; The internal fluid density variation along the riser, and; The 1st order platform motions applied to the top of riser; In addition to the results of this paper, some highlights are presented for SCR analysis in similar conditions.

A New Top Connection System for Steel Catenary Risers

2009 ◽  
Author(s):  
Claudio Marcio Silva Dantas ◽  
Jose´ Renato Mendes de Sousa ◽  
Fernando Jorge Mendes de Sousa ◽  
Marcos Queija de Siqueira ◽  
Isai´as Quaresma Masetti
Keyword(s):  
Fatigue Life ◽  
Line Segment ◽  
Mooring Line ◽  
Bending Moments ◽  
Connection System ◽  
Steel Catenary Risers ◽  
Flexible Jumper ◽  
Maximum Stresses ◽  
New System

PETROBRAS has been developing several studies in order to verify the structural feasibility of SCRs connected to production units such as FPSOs, semi-submersible and monocolumn platforms. Due to the great stresses developed at the top region as a consequence of the platforms rotation movements, robust stress joints or flex joints are always required to connect the SCRs to the platforms. However, those components may add high costs to any project, mainly where titanium is required. In attempt to avoid this fact, the objective of this work is to present a new top connection system called “Suspender”. This system is composed by the SCR, a mooring line segment, a flexible jumper and a “Y” shaped steel connector, and has the advantage of reducing the transmission of bending moments from the platform to the SCR. The performance of this alternative was compared to a more conventional one, composed by a SCR and a flex joint, and the obtained results indicate that this new system reduces the maximum stresses at the top region without changing the SCR behavior at the TDZ. It is also possible to extend the fatigue life by changing the SCR configuration.

Design Features of Risers for the Extendable Draft Platform (EDP)

2004 ◽  
Author(s):  
Lixin Xu ◽  
Qi Xu ◽  
Colin Hough ◽  
John Murray
Keyword(s):  
West Africa ◽  
Gulf Of Mexico ◽  
Environmental Conditions ◽  
Floating Platform ◽  
Design Features ◽  
Field Development ◽  
Wide Range ◽  
Steel Catenary Risers ◽  
Wave Induced

The Extendable Draft Platform (EDP) is a deep draft semisubmersible with an extendable heave suppression pontoon, designed as a drilling and production floating platform for deepwater field development. The EDP supports both top tensioned risers (TTRs) for dry-trees and steel catenary risers (SCRs) for export risers and subsea wells. The TTRs can be supported at their tops by tensioners mounted on the main deck, and the SCRs can be connected to the EDP either by porches external to hull or by pull-tubes internal to the hull columns. This paper discusses design features of the EDP risers, including TTR tensioning system and coupled effects on hull motion performances, riser keel guide design and wear allowances, and SCR hang-off options. Also investigated are the effects of the EDP’s low motions on the riser systems, for instance, the wave induced fatigue of SCRs is significantly improved for the EDP, in comparison with a conventional semisubmersible of similar payload. Furthermore, designs of the EDP as well as riser systems can be optimized for different prevailing environmental conditions, such as those of West Africa, Brazil, West of Shetland, and the Gulf of Mexico. The EDP provides an effective and reliable way to support dry-trees and SCRs for a wide range of deepwater applications.

Study on the Inwall Crack Extension and Fatigue Life Evaluation for Deep-Sea Steel Catenary Riser under Wave and Current Action

2012 ◽  
Vol 238 ◽  
pp. 358-361
Author(s):  
Bing Jun Si ◽  
Qiao Jin
Keyword(s):  
Fatigue Life ◽  
Deep Sea ◽  
Crack Extension ◽  
Element Model ◽  
Steel Catenary Riser ◽  
Linear Elastic ◽  
Steel Catenary Risers ◽  
Fatigue Life Evaluation ◽  
Elastic Fracture ◽  
Crack Growth Model

Aimed at deep-sea steel catenary risers(SCRs) transporting supercritical or dense CO2, this paper uses the macroscopic pipeline-transporting finite element model and the microscopic pipewall crack growth model to numerically simulate corrosive-inwall-defect-induced crack extension along radial direction for the deep-sea riser which is subjected to wave and current loads. Meanwhile, based on linear elastic fracture mechanics and fatigue crack extension theory, the effect of wave height on the fatigue life of the pipewall at touchdown zone is discussed. The above-mentioned study in this paper is expected to give a good reference to the similar study for oil&gas SCRs.

Alternative Method of Buoy Supporting Riser (BSR) Installation

2011 ◽  
Author(s):  
Ricardo Franciss ◽  
Enrique Casaprima Gonzales ◽  
Jose´ Carlos Lima de Almeida ◽  
Jairo Bastos de Arau´jo ◽  
Antonio Carlos Fernandes
Keyword(s):  
Fatigue Life ◽  
Field Test ◽  
Water Depth ◽  
Monitoring Systems ◽  
Deep Waters ◽  
Alternative Method ◽  
Sea Bottom ◽  
Campos Basin ◽  
Steel Catenary Risers ◽  
Flexible Risers

Due to the 2200m water depth and harsher environmental conditions, one option that Petrobras is considering for the production of the Pre-Salt fields is the use of a subsurface buoy known as a Buoy Supporting Riser (BSR). It is composed of a subsurface tethered buoy, flexible jumpers connecting the Floating Production Unit (FPU) to the BSR and Steel Catenary Risers (SCRs) connecting the BSR to the flowlines on the sea bottom. The main advantages of this system are that it decouples the FPU motions from the SCRs, reducing fatigue damage in the touch down zone. It may also be installed independently of the FPU, except for the flexible jumpers, which would reduce the risers load on the FPU. Petrobras has been studying this concept since 1997 and has established, as a final stage of the study, a field test with the actual installation of the BSR. This was performed through an alternative method using only Petrobras AHTS boats, in order to avoid critical and expensive resources such as lift barges. With the purpose of validating this new installation procedure, Petrobras performed the referred installation of a 27.2m × 27.2m square ring shaped buoy in Congro Field in the Campos Basin over a water depth of 500m. The buoy was positioned at 80m depth, where the incidence of loads caused by waves is negligible, thus increasing the fatigue life of risers. After the BSR installation, the riser pull-in procedure was also conduced. This paper describes why this technology is necessary for these fields and the model tests made to validate the installation procedures. It also discusses how Petrobras tested the pull-in operations for two flexible risers after the actual buoy was installed. Monitoring systems were designed to check all forces and displacements during the referred installation. These actions will consolidate the BSR technology for Petrobras leading to another riser system option for production in ultra deep waters.

SCR Application for Turret Moored FPSOs in West Africa

2008 ◽  
Author(s):  
Howard H. Wang ◽  
Wan C. Kan ◽  
Juan I. Orphee ◽  
Mark D. Crawford ◽  
Jim Sutherland ◽  
...  
Keyword(s):  
West Africa ◽  
Small Diameter ◽  
Development Program ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Diameter Pipe ◽  
Compressive Loads ◽  
High Fatigue ◽  
Steel Catenary Risers ◽  
Weld Fatigue

Turret moored Floating Production Storage and Offloading (FPSO) systems with flexible risers have been successfully used in many deepwater developments in West Africa. However, Steel Catenary Risers (SCR) have not been used on a turret moored FPSO because of concerns with the riser fatigue and compression loading due to the large FPSO motions at the turret location. ExxonMobil has initiated a development program to establish the feasibility of SCRs on turret moored FPSOs. The goal of this work effort is enable the use of SCRs on West African turret-moored FPSOs and thereby expand the riser concept options to bring potential economic advantage for future prospects. Additionally, the SCRs may be needed to comply with local content requirements. The development program consists of identifying the limitations of a conventional SCR design, establishing feasible SCR concepts that meet the strength and fatigue requirements, and pre-qualification of a high fatigue performance welding technology. The program focuses on alternate SCR concepts including SCRs with locally weighted and buoyant sections. This paper presents the SCR concepts and the associated analysis results which demonstrate the elimination of compressive loads in the touch down area and the achievement of adequate weld fatigue performance throughout the riser. This paper further presents the results of the inconel weld pre-qualification program including fatigue tests on large and small diameter pipe to demonstrate enhanced fatigue performance.

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