UMBILICALS AND RISERS 623

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UMBILICALS AND RISERS 623 7 Steel Catenary Risers


Unit Presenter Mr Kevin Mullen

Mr Mullen has 38 years engineering experience, with 24 years in the offshore oil and gas industry, specialising in subsea systems, with expertise in subsea control systems and umbilicals.

He gained experience of offshore oil and gas in the North Sea and Atlantic margin, and came to Australia to work on big gas 16 years ago.

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DISCLAIMER This presentation has been prepared by a representative of WorleyParsons.

The presentation contains the professional and personal opinions of the presenter, which are given in good faith. As such, opinions presented herein may not always necessarily reflect the position of WorleyParsons as a whole, its officers or executive.

Any forward-looking statements included in this presentation will involve subjective judgment and analysis and are subject to uncertainties, risks and contingencies—many of which are outside the control of, and may be unknown to, WorleyParsons.

WorleyParsons and all associated entities and representatives make no representation or warranty as to the accuracy, reliability or completeness of information in this document and do not take responsibility for updating any information or correcting any error or omission that may become apparent after this document has been issued.

To the extent permitted by law, WorleyParsons and its officers, employees, related bodies and agents disclaim all liability—direct, indirect or consequential (and whether or not arising out of the negligence, default or lack of care of WorleyParsons and/or any of its agents)—for any loss or damage suffered by a recipient or other persons arising out of, or in connection with, any use or reliance on this presentation or information.

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1. Introduction

2. History

3. Materials

4. Wall Thickness Sizing

5. SCR Design Analysis

6. Welding Technology

7. Hang-offs

8. Strength Design Challenges and Solutions

9. Fatigue Design Challenges and Solutions

10. Integrity Monitoring and Management Systems

11. Determining Factors in Configuration Design

Lecture Outline

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1. Introduction

The simple catenary Can pipe really bend like this?

5 Courtesy en.wikipedia.org- lymcanada.org- www.gateinc.com-


1.

How do we build a structure like this? Is it as simple as this?

6 Courtesy Subsea Pipelines and Risers by Yong Bai and Qiang Bai


1.

How do we build a structure like this? Is it as simple as this?

7 Courtesy OTC 20994


1. Introduction

The touchdown point Generally highly stressed



2. History

First SCRs in 1993 Shell's Auger TLP in the Gulf of Mexico

9 Courtesy OTC 7620


2. History

The first SCR to a semi-submersible in 1997 Marlim Field, offshore Brazil

10 Courtesy http://www.mcskenny.com/downloads/Petrobras%20PXVIII.pdf


2. History

First reeled SCRs installed on a TLP in 2003 8" and 10" Matterhorn export SCRs in the Gulf of Mexico



2. History

First pipe-in-pipe SCRs in 2003 Shell Na Kika in the Gulf of Mexico

12 Courtesy http://www.offshore-technology.com/projects/na_kika/na_kika5.html


2. History

First SCRs to be installed on an FPSO in 2004 Shell Bonga offshore West of Africa.



2. History

Steel Lazy Wave Risers (SLWR) first installed in 2009 Installed by Subsea7 for Shell in Brazil for BC-10 Project.



3. Materials

Riser pipe material grades API 5L X60, X65 and X-70

Corrosion coating materials FBE, 3LPE and 3LPP.

Anti-abrasion coatings HDPE and HDPP.

Thermal insulation coatings GSPU, multi-layer PP and PUF


7 layer insulation system


3. Materials

Sour Services and Clad Pipe Metallurgically Bonded Pipes: They are those in which there is a metallurgical bond between the structural outer pipe and the corrosion resistant inner pipe.

Mechanically Lined Pipes: The simplest and most economical method of producing clad pipe is to internally line carbon steel pipes.



4. Wall Thickness Sizing

Sized to pressure containment (hoop and burst strength) Requirement such as API RP 1111 and CFR

Reeling Diameter to thickness (D/t) ratio

On-bottom axial and lateral stability requirement Wall thickness may have to be increased

API 2RD combined (von Mises) stress check




Initial Design – define: Riser host layout (for interface with other disciplines) Riser hang-off system (flex joint, stress joint and pull-tube etc) Riser hang-off location, spacing and azimuth angle (hull layout, subsea layout, total risers and interference consideration)

Riser hang-off angle for each riser Riser location elevation at hull (hull type, installation and fatigue consideration)

Global static configuration




Strength and Fatigue Analysis – to confirm: Extreme response meet the stress criteria per API 2RD and extreme rotation for flexjoints

VIV fatigue life and the required length of strakes (or fairing) Wave fatigue life Interference between risers and with floater hull




High fatigue demands S-N Curves and SCF for Welded Connections




Engineering Critical Assessment (ECA) A tool that links flaw geometry with material properties and the stress ranges Flaw size calculated from the ECA analysis is used as acceptance criteria for UT inspections

21 Courtesy http://www.twi-global.com/technical-knowledge/faqs/structural-integrity-faqs/faq-engineering-critical-assessment-eca/



UT Inspections and ECA Criteria Ultrasonic (UT) is usually integrated into an Engineering Critical Assessment (ECA) approach.

22 Courtesy pipelineandgasjournal.com- and www.aitechnologies


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What is ECA and where it can be used?

Self Assessment Question


What is ECA and where it can be used?

Engineering Critical Assessment is a tool that links flaw geometry with material

properties and the stress ranges. Flaw size calculated from the ECA analysis is

used as acceptance criteria for UT inspections

ECA can be used: 1.During design, to assist in the choice of welding procedure and/or inspection techniques. 2.During fabrication, to assess the significance of: a) known defects which are unacceptable to a given fabrication code, or b) a failure to meet the toughness requirements of a fabrication code. 3.During operation, to assess flaws found in service and to make decisions as to whether they can safely remain, or whether down-rating/repair is necessary.

Self Assessment Answer

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7. Hang-offs

Flexjoints Flexjoint allows the riser system to rotate with minimum bending moment

25 Courtesy www.intechopen.com-


7. Hang-offs

Stressjoints Flexjoint allows the riser system to rotate with minimum bending moment

26 Courtesy SCR Hang-Off System Selection Considerations and Criteria , Yingying Wang, ISOPE 2011



Strength Design Issues High SCR hang-off tensions SCR touchdown zone effective compression SCR touchdown zone stress




Solutions to reduce bottom compression of an SCR Minimise the SCR hang-off motion. Increase the wall thickness in the touchdown region Weight Distributed SCR concept (Karunakaran, 2006) Lazy Wave SCR (2H Offshore)

31 Courtesy Design and Analysis of Steel Catenary Riser Systems for Deep Waters, Thomas Buberg



Solutions to reduce bottom compression of an SCR Buoyancy Supported SCR system (Milne, G. Subsea 7, 2012)

32 Courtesy Design and Analysis of Steel Catenary Riser Systems for Deep Waters, Thomas Buberg


What solutions can be used to reduce bottom compression of an SCR ?

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What solutions can be used to reduce bottom compression of an SCR ?

Minimise the SCR hang-off motion Increase the wall thickness in the touchdown region Weight Distributed SCR concept (Karunakaran, 2006) Lazy Wave SCR (2H Offshore)

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Fatigue Issues Waves and hull motions SCR vortex induced vibrations (VIV) Hull VIV induced motions (VIM) Hull heave motions Installation fatigue


Fatigue Sensitive Zones



Fatigue Issues VIV Design Challenges

36 Courtesy Deep Water Steel Catenary Systems Installation, Marin Abélanet, Subsea 7

VIV Strakes going through Stinger Rollers, mounted under J-Lay Tower



Fatigue Issues Fatigue Due to Hull Heave Motions and VIM

37 Courtesy Aker Kvaerner



Fatigue Issues Effect of Wall-thickness Tolerance on Submerged Weight and Fatigue




Fatigue Issues Touchdown Soil Effect

39 Courtesy Re-penetration Pipe/Soil Interaction Curves (Bridge et al., 2004)



Fatigue Design Solutions Optimization of the hull shape Move the vessel location a number of times Metocean prediction models Risk-related integrity management plan with VIV monitoring Use of a higher safety factor for VIV design




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What are the Fatigue Issues that can damage SCRs?



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What are the Fatigue Issues that can damage SCRs?

Fatigue Issues that can damage SCRs are Waves and hull motions SCR vortex induced vibrations (VIV) Hull VIV induced motions (VIM) Hull heave motions Installation fatigue


10. Integrity Monitoring and Management Systems

Monitoring Systems Flexjoint angle Riser top tension force and Riser stress levels

Integrity Management Using Monitored Data Monitored data may be used to manage structural integrity


Motion loggers installed on a riser help assess fatigue


11. Determining Factors in Configuration Design Factors to consider

Water depth Fatigue Field layout Welding Installation Method

44 Courtesy Design and Analysis of Steel Catenary Riser Systems for Deep Waters, Thomas Buberg Steel Catenary Riser Pull-in at Thunder Horse by Christian Schonfeld, HMC and George Zener, BP

UMBILICALS AND RISERS 623

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