SUBSEA PIPELINES AND RISERS

YONG BAI

and

QIANG BAI

2005

ELSEVIER

Amsterdam - Boston - Heidelberg - London - New York - OxfordParis - San Diego - San Francisco - Singapore - Sydney - Tokyo

TABLE OF CONTENTS

Foreword vForeword to "Pipelines and Risers" Book viiPreface ix

PART I: Mechanical Design

Chapter 1 Introduction 31.1 Introduction 31.2 Design Stages and Process 3

1.2.1 Design Stages 31.2.2 Design Process 6

1.3 Design Through Analysis (DTA) 91.4 Pipeline Design Analysis 11

1.4.1 General 111.4.2 Pipeline Stress Checks 111.4.3 Span Analysis 131.4.4 On-bottom Stability Analysis 141.4.5 Expansion Analysis 171.4.6 Buckling Analysis 171.4.7 Pipeline Installation 19

1.5 Pipeline Simulator 211.6 References 24

Chapter 2 Wall-thickness and Material Grade Selection 252.1 Introduction 25

2.1.1 General 252.1.2 Pipeline Design Codes 25

2.2 Material Grade Selection 262.2.1 General Principle 262.2.2 Fabrication, Installation and Operating Cost Considerations 272.2.3 Material Grade Optimization 28

2.3 Pressure Containment (hoop stress) Design 282.3.1 General 282.3.2 Hoop Stress Criterion of DNV (2000) 292.3.3 Hoop Stress Criterion of ABS (2000) 302.3.4 API RP1111 (1998) 31

2.4 Equivalent Stress Criterion 332.5 Hydrostatic Collapse 342.6 Wall Thickness and Length Design for Buckle Arresters 362.7 Buckle Arrester Spacing Design 372.8 References 39

Chapter 3 Buckling/Collapse of Deepwater Metallic Pipes 413.1 Introduction 413.2 Pipe Capacity under Single Load 42

3.2.1 General 423.2.2 External Pressure 433.2.3 Bending Moment Capacity 463.2.4 Pure Bending 483.2.5 Pure Internal Pressure 483.2.6 Pure Tension 483.2.7 Pure Compression 48

3.3 Pipe Capacity under Couple Load 493.3.1 Combined Pressure and Axial Force 493.3.2 Combined External Pressure and Bending 50

Contents

\xial Force and Bending 51:d Area in Compression 52the Fully Plastic Neutral Axis 53ment 54

5858

on versus Finite Element Results 59> Subjected to Single Loads 59i Subjected to Combined Loads 61

65d Strength Design 67

67/iceability Limit 68

: 69Equivalent Stress Criteria 69Criteria for Pipeline 69

ise 7074

ent 74Assessment 75

7777

nt Based on S-N Curves 77nt Based on Ae-N Curves 78

78eria 79train 79; Field Joints Due to Coatings 80

80

Design

eraction 8383

I 83Method 83

8485

Breakout Forces 86m 86

8788

iround Pipes 8989

• 8 9ions Used in the Wave Simulators 89

89:rested Waves 90crested Waves 91

9595

ig and Inertia Forces 95t Forces 99

100lalysis of In-situ Behavior 101

101: Element Model 102blems 102

Contents xiii

7.2.2 Dynamic Analysis Problems 1047.3 Steps in an Analysis and Choice of Analysis Procedure 105

7.3.1 The Static Analysis Procedure 1057.3.2 The Dynamic Analysis Procedure 106

7.4 Element Types Used in the Model 1067.5 Non-linearity and Seabed Model 108

7.5.1 Material Model 1087.5.2 Geometrical Non-linearity 1097.5.3 Boundary Conditions 1097.5.4 Seabed Model 109

7.6 Validation of the Finite Element Model 1097.7 Dynamic Buckling Analysis 1117.8 Cyclic In-place Behaviour during Shutdown Operations 1137.9 References 114

Chapter 8 Expansion, Axial Creeping, Upheaval/Lateral Buckling 1158.1 Introduction 1158.2 Expansion 115

8.2.1 General Principle 1158.2.2 Single Flowlines 116

8.3 Axial Creeping of Flowlines Caused by Soil Ratcheting 1178.3.1 General 1178.3.2 Cyclic Soil/Pipe Interaction Model 1178.3.3 Expansion of a "Long" Flowline with Free ends 1188.3.4 In-situ Expansion Behavior of the Creeping Flowlines 119

8.4 Upheaval Buckling 1208.4.1 General 1208.4.2 Analysis of Up-lifts 1208.4.3 Upheaval Movements 124

8.5 Lateral Buckling 1258.5.1 General 1258.5.2 Lateral Buckling of Straight Line on Flat Seabed 125

8.6 Interaction between Lateral and Upheaval Buckling 1268.7 References 128

Chapter 9 On-bottom Stability 1299.1 Introduction 1299.2 Force Balance: the Simplified Method 1299.3 Acceptance Criteria 130

9.3.1 Allowable Lateral Displacement 1309.3.2 Limit-state Strength Criteria 130

9.4 Special Purpose Program for Stability Analysis 1309.4.1 General 1309.4.2 PONDUS 1319.4.3 PIPE 133

9.5 Use of FE Analysis for Intervention Design 1339.5.1 Design Procedure 1339.5.2 Seabed Intervention 1339.5.3 Effect of Seabed Intervention 135

9.6 References 136Chapter 10 Vortex-induced Vibrations (VIV) and Fatigue 137

10.1 Introduction 13710.2 Free-span VIV Analysis Procedure 139

10.2.1 Structural Analysis 13910.2.2 Hydrodynamic Description , 13910.2.3 Soil Stiffness Analysis 14110.2.4 Vibration Amplitude and Stress Range Analysis 14310.2.5 Fatigue Model 143

10.3 Fatigue Design Criteria 14410.3.1 Accumulated Fatigue Damage 14410.3.2 S-N Curves 144

xiv Contents

10.4 Response Amplitude 14410.4.1 In-line VIV in Current Dominated Conditions 14410.4.2 Cross-flow VIV in Combined Wave and Current 147

10.5 Modal Analysis 14810.5.1 General 14810.5.2 Single Span Modal Analysis 14910.5.3 Multiple Span Modal Analysis 149

10.6 Example Cases 15010.6.1 General 15010.6.2 Fatigue Assessment 152

10.7 References 154Chapter 11 Force Model and Wave Fatigue 155

11.1 Introduction 15511.2 Fatigue Analysis 155

11.2.1 Fatigue of Free-spanning Pipelines 15511.2.2 Fatigue Damage Assessment Procedure 15811.2.3 Fatigue Damage Acceptance Criteria 15911.2.4 Fatigue Damage Calculated Using Time Domain Solution 15911.2.5 Fatigue Damage Calculated Using Frequency Domain Solution 160

11.3 Force Model 16111.3.2 Modal Analysis 16311.3.3 Time Domain Solution 16411.3.4 Frequency Domain Solution 168

11.4 Comparisons of Frequency Domain and Time Domain Approaches 17011.5 Conclusions and Recommendations 17111.6 References 172

Chapter 12 Trawl Impact, Pullover and Hooking Loads 17312.1 Introduction 17312.2 Trawl Gears 173

12.2.1 Basic Types of Trawl Gear 17312.2.2 Largest Trawl Gear in Present Use 174

12.3 Acceptance Criteria 17412.3.1 Acceptance Criteria for Impact Response Analyses 17412.3.2 Acceptance Criteria for Pullover Response Analyses 175

12.4 Impact Response Analysis 17512.4.1 General 17512.4.2 Methodology for Impact Response Analysis 17512.4.3 Steel Pipe and Coating Stiffness 17812.4.4 Trawl Board Stiffness, Mass and Hydrodynamic Added Mass 18112.4.5 Impact Response 183

12.5 Pullover Loads 18412.6 Finite Element Model for Pullover Response Analyses 186

12.6.1 General 18612.6.2 Finite Element Models 18612.6.3 Analysis Methodology 187

12.7 Case Study 18812.7.1 General 18812.7.2 Trawl Pull-over for Pipelines on an Uneven Seabed 188

12.8 References 194Chapter 13 Pipe-in-pipe and Bundle Systems 195

13.1 Introduction 19513.2 Pipe-in-pipe System 195

13.2.1 General 19513.2.2 Why Pipe-in-pipe Systems 19613.2.3 Configuration 19713.2.4 Structural Design and Analysis 19813.2.5 Wall-thickness Design and Material Selection 20013.2.6 Failure Modes 20113.2.7 Design Criteria 201

Contents xv

13.2.8 Insulation Considerations 20313.2.9 Fabrication and Field Joints 20313.2.10 Installation 204

13.3 Bundle System 20513.3.1 General 20513.3.2 Bundle Configurations 20613.3.3 Design Requirements for Bundle System 20613.3.4 Bundle Safety Class Definition 20713.3.5 Functional Requirement 20713.3.6 Insulation and Heat-up System 20813.3.7 Umbilicals in Bundle 20913.3.8 Design Loads 20913.3.9 Installation by CDTM 216

13.4 References 218Chapter 14 Seismic Design 219

14.1 Introduction 21914.2 Pipeline Seismic Design Guidelines 220

14.2.1 Seismic Design Methodology 22014.2.2 Seismic Level of Design 22314.2.3 Analysis Examples 223

14.3 Conclusions 22814.4 References 228

Chapter 15 Corrosion Prevention 22915.1 Introduction 22915.2 Fundamentals of Cathodic Protection 22915.3 Pipeline Coatings 231

15.3.1 Internal Coatings 23115.3.2 External Coatings 231

15.4 CP Design Parameters 23215.4.1 Design Life 23215.4.2 Current Density 23215.4.3 Coating Breakdown Factor 23415.4.4 Anode Material Performance 23515.4.5 Resistivity 23515.4.6 Anode Utilization Factor 235

15.5 Galvanic Anodes System Design 23615.5.1 Selection of Anodes Type 23615.5.2 CP Design Practice 23715.5.3 Anode Spacing Determination 23815.5.4 Commonly Used Galvanic Anodes 23815.5.5 Pipeline CP System Retrofit 23915.5.6 Internal Corrosion Inhibitors : 239

15.6 References 240Chapter 16 Asgard Flowlines Design Examples 241

16.1 Introduction 24116.2 Wall-thickness and Linepipe Material Selection 242

16.2.1 General 24216.2.2 Linepipe Material Selection 24216.2.3 Wall-thickness Design 242

16.3 Limit State Strength Criteria 24316.3.1 General 24316.3.2 Bursting Under Combined Loading 24316.3.3 Local Buckling/Collapse 24316.3.4 Fracture 24416.3.5 Low-cycle Fatigue 24416.3.6 Ratcheting 245

16.4 Installation and On-bottom Stability 24716.4.1 Installation Design 24716.4.2 On-bottom Stability 248

xvi Contents

16.5 Design for Global Buckling, Fishing Gear Loads and VIV 24916.5.1 General 24916.5.2 Global Buckling 25016.5.3 Trawlboard 25216.5.4 Vortex Induced Vibrations (VIV) 255

16.6 Asgard Transport Project 25816.7 References 258

PART III: Flow Assurance

Chapter 17 Subsea System Engineering 26317.1 Introduction 263

17.1.1 Flow Assurance Challenges 26317.1.2 Flow Assurance Concerns 264

17.2 Typical Flow Assurance Process 26517.2.1 General 26517.2.2 Fluid Characterization and Property Assessments 26517.2.3 Steady State Hydraulic and Thermal Performance Analyses 26817.2.4 Transient Hydraulic and Thermal Performances Analyses 268

17.3 System Design and Operability 27217.3.1 Well Start-up & Shut-in 27317.3.2 Flowline Blowdown 275

17.4 References 276Chapter 18 Hydraulics 277

18.1 Introduction 27718.2 Composition and Properties of Hydrocarbons 277

18.2.1 Hydrocarbons Composition 27718.2.2 Equation of State 27918.2.3 Hydrocarbons Properties 280

18.3 Emulsion 28218.3.1 General , 28218.3.2 Effect of Emulsion on Viscosity 28318.3.3 Prevention of Emulsion 285

18.4 Phase Behavior 28518.4.1 Black Oils 28618.4.2 Volatile Oils 28618.4.3 Condensate 28618.4.4 Wet Gases 28718.4.5 Dry Gases 28718.4.6 Computer Models ; 288

18.5 Hydrocarbon Flow 28918.5.1 General 28918.5.2 Single-phase Flow 29018.5.3 Multi-phase Flow 29518.5.4 Comparison of Two-phase Flow Correlations 298

18.6 Slugging and Liquid Handling 30218.6.1 General 30218.6.2 Hydrodynamic Slugging 30418.6.3 Terrain Slugging 30518.6.4 Start-up Slugging 30618.6.5 Pigging 30618.6.6 Slugging Prediction 30718.6.7 Slug Detection and Control Systems 30818.6.8 Slug Catcher Sizing 308

18.7 Pressure Surge 30818.7.1 Fundamentals of Pressure Surge 30818.7.2 When Is Pressure Surge Analysis Required? 309

18.8 Line Sizing 310

Contents xvii

18.8.1 Hydraulic Calculation 31018.8.2 Criteria 31118.8.3 Maximum Operating Velocities 31218.8.4 Minimum Operation Velocities 31318.8.5 Wells 31318.8.6 Gas Lift 314

18.9 References 315Chapter 19 Heat Transfer and Thermal Insulation 317

19.1 Introduction 31719.2 Heat Transfer Fundamentals 318

19.2.1 Heat Conduction 31819.2.2 Convection 32019.2.3 Buried Pipeline Heat Transfer 32319.2.4 Soil Thermal Conductivity 325

19.3 U-value 32619.3.1 Overall Heat Transfer Coefficient 32619.3.2 Achievable U-values 32919.3.3 U-value for Buried Pipe 330

19.4 Steady State Heat Transfer 33119.4.1 Temperature Prediction along Pipeline 33119.4.2 Steady State Insulation Performance 332

19.5 Transient Heat Transfer 33319.5.1 Cool Down 33419.5.2 Transient Insulation Performance 337

19.6 Thermal Management Strategy and Insulation 33819.6.1 External Insulation Coating System 34019.6.2 Pipe-in-pipe System 34419.6.3 Bundling 34619.6.4 Burial 34619.6.5 Direct Heating 34719.6.6 Hot Fluid Heating (Indirect Heating) 349

19.7 References 34919.8 Appendix: U-value and Cooldown Time Calculation Sheet 351

Chapter 20 Hydrates 35720.1 Introduction 35720.2 Physics and Phase Behavior 359

20.2.1 General 35920.2.2 Hydrate Formation and Dissociation 36020.2.3 Effects of Salt, MeOH, Gas Composition 36320.2.4 Mechanism of Hydrate Inhibition 365

20.3 Hydrate Prevention 36720.3.1 Thermodynamic Inhibitors 36820.3.2 Low-dosage Hydrate Inhibitors 36920.3.3 Low Pressure 36920.3.4 Water Removal 37020.3.5 Thermal Insulation 37020.3.6 Active Heating 370

20.4 Hydrate Remediation 37120.4.1 Depressurization 37220.4.2 Thermodynamic Inhibitors 37320.4.3 Active Heating 37320.4.4 Mechanical Methods 37420.4.5 Safety Considerations 374

20.5 Hydrate Control Design Philosophies 37420.5.1 Selection of Hydrate Control 37420.5.2 Cold Flow Technology 37820.5.3 Hydrates Control Design Process 37920.5.4 Hydrates Control Design and Operation Guideline 379

20.6 Recover of Thermodynamic Hydrate Inhibitors 380

xviii Contents

20.7 References 382Chapter 21 Wax and Asphaltenes 383

21.1 Introduction 38321.2 Wax 383

21.2.1 General 38321.2.2 Wax Formation 38421.2.3 Viscosity of Waxy Oil 38721.2.4 Gel Strength 38721.2.5 Wax Deposition 38721.2.6 Wax Deposition Prediction 388

21.3 Wax Management 38921.3.1 General 38921.3.2 Thermal Insulation 38921.3.3 Pigging 39021.3.4 Inhibitor Injection 390

21.4 Wax Remediation 39021.4.1 Wax Remediation Methods 39121.4.2 Assessment of Wax problem 39221.4.3 Wax Control Design Philosophies 392

21.5 Asphaltenes 39221.5.1 General 39221.5.2 Assessment of Asphaltene Problem 39321.5.3 Asphaltene Formation 39521.5.4 Asphaltene Deposition 396

21.6 Asphaltenes Control Design Philosophies 39621.7 References 398

PART IV: Riser EngineeringChapter 22 Design of Deepwater Risers 401

22.1 Description of a Riser System 40122.1.1 General 40122.1.2 System Descriptions 40122.1.3 Flexible Riser Global Configuration 40222.1.4 Component Descriptions 40422.1.5 Catenary and Top Tensioned Risers 406

22.2 Riser Analysis Tools 40722.3 Steel Catenary Riser for Deepwater Environments 408

22.3.1 Design Codes 40822.3.2 Analysis Parameters 40922.3.3 Soil-Riser Interaction 40922.3.4 Pipe Buckling Collapse under Extreme Conditions 41022.3.5 Vortex Induced Vibration Analysis 410

22.4 Stresses and Service Life of Flexible Pipes 41022.5 Drilling and Workover Risers 41122.6 References 411

Chapter 23 Design Codes for Risers and Subsea Systems 41323.1 Introduction 41323.2 Design Criteria for Deepwater Metallic Risers 414

23.2.1 Design Philosophy and Considerations 41423.2.2 Currently Used Design Criteria 41523.2.3 Ultimate Limit State Design Checks 415

23.3 Limit State Design Criteria 41523.3.1 Failure Modes and Limit States 41523.3.2 Acceptance Criteria 416

23.4 Loads, Load Effects and Load Cases 41623.4.1 Loads and Load Effects 41623.4.2 Definition of Load Cases 417

Contents xix

23.4.3 Load Factors 41723.5 Improving Design Codes and Guidelines 418

23.5.1 General 41823.5.2 Flexible Pipes 41823.5.3 Metallic Risers 421

23.6 Regulations and Standards for Subsea Production Systems 42123.7 References 422

Chapter 24 VIV and Wave Fatigue of Risers 42324.1 Introduction 42324.2 Fatigue Causes 423

24.2.1 Wave Fatigue 42324.2.2 VIV Induced Fatigue 425

24.3 Riser VIV Analysis and Suppression 42624.3.1 VIV Predictions 42624.3.2 Theoretical Background 42724.3.3 Riser VIV Analysis Software 42824.3.4 Vortex-induced Vibration Suppression Devices 42924.3.5 VIV Analysis Example 430

24.4 Riser Fatigue due to Vortex-induced Hull Motions (VIM) 43124.4.1 General 43124.4.2 VIM Amplitudes 43224.4.3 Riser Fatigue due to VIM 43324.4.4 VIM Stress Histograms 43424.4.5 Sensitivity Analysis 435

24.5 Challenges and Solutions for Fatigue Analysis 43524.6 Conclusions 43524.7 References 436

Chapter 25 Steel Catenary Risers 43725.1 Introduction 43725.2 SCR Technology Development History 43825.3 Material Selection, Wall-thickness Sizing, Source Services and Clap Pipe 439

25.3.1 Wall Thickness Sizing 43925.3.2 Sour Services and Clad Pipe 440

25.4 SCR Design Analysis 44025.4.1 Initial Design 44025.4.2 Strength and Fatigue Analysis 441

25.5 Welding Technology, S-N Curves and SCF for Welded Connections 44125.5.1 Welding Technology 44125.5.2 S-N Curves and SCF for Welded Connections 442

25.6 UT Inspections and ECA Criteria 44225.7 Flexjoints, Stressjoints and Pulltubes 444

25.7.1 Flexjoints 44425.7.2 Stressjoints 44525.7.3 Pulltubes 445

25.8 Strength Design Challenges and Solutions 44525.8.1 Strength Design Issues 44525.8.2 SCR Hang-off Tensions 44525.8.3 SCR Touchdown Zone Effective Compression 44625.8.4 SCR Touchdown Zone Stress 44625.8.5 Strength Design Solutions 446

25.9 Fatigue Design Challenges and Solutions 44625.9.1 Fatigue Issues 44625.9.2 VIV Design Challenges 44625.9.3 Fatigue Due to Hull Heave Motions and VIM 44725.9.4 Effect of Wall-thickness Tolerance on Submerged Weight and Fatigue 44725.9.5 Effect of Vessel Selection, Hang-off Angle, Riser Orientation 44725.9.6 Combined Frequency and Time Domain Analysis 44825.9.7 Touchdown Soil Effect 44825.9.8 Fatigue Design Solutions 448

xx Contents

25.10 Installation and Sensitivity Considerations 44925.10.1 Installation Considerations 44925.10.2 Sensitivity Analysis Considerations 449

25.11 Integrity Monitoring and Management Systems 45025.11.1 Monitoring Systems 45025.11.2 Integrity Management Using Monitored Data 450

25.12 References 450Chapter 26 Top Tensioned Risers 453

26.1 Introduction 45326.2 Top Tension Risers Systems 454

26.2.1 Configuration 45426.2.2 General Design Considerations 45726.2.3 Drilling Risers 458

26.3 TTR Riser Components 45826.3.1 General 45826.3.2 Dry Tree Riser Tensioner System 45826.3.3 Tie-back Connector 45926.3.4 Keel Joint 45926.3.5 Tapered Stress Joint 46126.3.6 Riser Joint Connectors 46126.3.7 Tension Joint & Ring 46326.3.8 Riser Joint in Splash Zone 46426.3.9 Flexible Jumper between Surface Tree and Deck-based Manifold 46426.3.10 Tubing/Casing Hanger 46426.3.11 Air Cans 46526.3.12 Distributed Buoyancy Foam 466

26.4 Modelling and Analysis of Top Tensioned Risers 46726.4.1 General ; 46726.4.2 Stack-up Model and Tension Requirement 46826.4.3 Composite Riser Section 46926.4.4 Vessel Boundary Conditions 47026.4.5 Soil Conditions 47026.4.6 Modelling of Riser Components 47126.4.7 Installation Analysis 474

26.5 Integrated Marine Monitoring System 47526.5.1 General 47526.5.2 IMMS System 47526.5.3 Use of the Monitored Data 476

26.6 References 476Chapter 27 Steel Tube Umbilical & Control Systems 477

27.1 Introduction 47727.1.1 General 47727.1.2 Feasibility Study 47827.1.3 Detailed Design and Installation 47927.1.4 Qualification Tests : 480

27.2 Control Systems 48027.2.1 General 48027.2.2 Control Systems 48027.2.3 Elements of Control System 48127.2.4 Umbilical Technological Challenges and Solutions 482

27.3 Cross-sectional Design of the Umbilical 48527.4 Steel Tube Design Capacity Verification 486

27.4.1 Pressure Containment 48627.4.2 Allowable Bending Radius 486

27.5 Extreme Wave Analysis 48727.6 Manufacturing Fatigue Analysis 488

27.6.1 Accumulated Plastic Strain 48827.6.2 Low Cycle Fatigue 489

27.7 ln-place Fatigue Analysis 489

Contents xxi

27.7.1 Selection of Seastate Data from Wave Scatter Diagram 49027.7.2 Analysis of Finite Element Static Model 49027.7.3 Umbilical Fatigue Analysis Calculations 49027.7.4 Simplified or Enhanced Approach 49127.7.5 Generation of Combined Stress History 49227.7.6 Rainflow Cycle Counting Procedure or Spectral Fatigue Analysis 49327.7.7 Incorporation of Mean Stress Effects in Histogram 493

27.8 Installation Analysis 49427.9 Required On-seabed Length for Stability 49527.10 References .- 495

Chapter 28 Flexible Risers and Flowlines 49728.1 Introduction 49728.2 Flexible Pipe Cross Section 497

28.2.1 Carcass 49928.2.2 Internal Polymer Sheath 50028.2.3 Pressure Armor 50028.2.4 Tensile Armor 50028.2.5 External Polymer Sheath 50128.2.6 Other Layers and Configurations 501

28.3 End Fitting and Annulus Venting Design 50128.3.1 End Fitting Design and Top Stiffener (or Bellmouth) 50128.3.2 Annulus Venting System 502

28.4 Flexible Riser Design : 50328.4.1 Design Analysis 50328.4.2 Riser System Interface Design 50428.4.3 Current Design Limitations 506

28.5 References 507Chapter 29 Hybrid Risers 509

29.1 Introduction 50929.2 General Description of Hybrid Risers 511

29.2.1 Riser Foundation 51129.2.2 Riser Base Spools 51229.2.3 Top and Bottom Transition Forging 51329.2.4 Riser Cross-section 51329.2.5 Buoyancy Tank 51329.2.6 Flexible Jumpers 514

29.3 Sizing of Hybrid Risers , 51429.3.1 Riser Cross-section 51429.3.2 Buoyancy Tanks 51529.3.3 Riser Foundation 51629.3.4 Flexible Jumpers 517

29.4 Preliminary Analysis 51829.5 Strength Analysis 51929.6 Fatigue Analysis 52029.7 Structural and Environmental Monitoring System 520

29.7.1 Riser Fatigue Monitoring Approach 52129.7.2 Structural Monitoring System 52129.7.3 Environmental Monitoring System 52229.7.4 Vessel Mooring and Position 523

29.8 References 523Chapter 30 Drilling Risers 525

30.1 introduction 52530.2 Floating Drilling Equipments 526

30.2.1 Completion and Workover (C/WO) Risers 52630.2.2 Diverter and Motion Compensating Equipment 53030.2.3 Choke and Kill Lines and Drill String 531

30.3 Key Components of Subsea Production Systems 53230.3.1 Subsea Wellhead Systems 53230.3.2 BOP 532

xxii Contents

30.3.3 Tree and Tubing Hanger System 53330.4 Riser Design Criteria 533

30.4.1 Operability Limits 53330.4.2 Component Capacities 534

30.5 Drilling Riser Analysis Model 53430.5.1 Drilling Riser Stack-up Model 53430.5.2 Vessel Motion Data 53530.5.3 Environmental Conditions 53530.5.4 Cyclic P-y Curves for Soil 536

30.6 Drilling Riser Analysis Methodology 53630.6.1 Running and Retrieve Analysis 53630.6.2 Operability Analysis 53930.6.3 Weak Point Analysis 54030.6.4 Drift-off Analysis 54130.6.5 VIV Analysis 54230.6.6 Wave Fatigue Analysis 54330.6.7 Hang-off Analysis 54330.6.8 Dual Operation Interference Analysis 54430.6.9 Contact Wear Analysis 54530.6.10 Recoil Analysis 546

30.7 References 547Chapter 31 Integrity Management of Flexibles and Umbilicals 549

31.1 Introduction 54931.2 Failure Statistics 55031.3 Risk Management Methodology 55231.4 Failure Drivers 552

31.4.1 Temperature 55231.4.2 Pressure 55331.4.3 Product Fluid Composition 55431.4.4 Service Loads 55431.4.5 Ancillary Components 555

31.5 Failure Modes 55531.5.1 Fatigue 55531.5.2 Corrosion 55531.5.3 Erosion 55631.5.4 Pipe Blockage or Flow Restriction 55631.5.5 Accidental Damage 556

31.6 Integrity Management Strategy 55631.6.1 Flexible Pipe Integrity Management System 55631.6.2 Installation Procedures 55831.6.3 Gas Diffusion Calculations 55831.6.4 Dropped Object Reporting/Deck Lifting & Handling Procedures 55831.6.5 Vessel Exclusion Zone 55831.6.6 Fatigue Life Re-analysis of Pipes 55831.6.7 High Integrity Pressure Protection System (HIPPS) 558

31.7 Inspection Measures 55831.7.1 General Visual Inspection (GVI) / Close Visual Inspection (CVI) 55831.7.2 Cathodic Protection Survey 559

31.8 Monitoring 55931.8.1 Inspection and Monitoring Systems 55931.8.2 Bore Fluid Parameter Monitoring 559

31.9 Testing and Analysis Measures 56031.9.1 Coupon Sampling and Analysis 56031.9.2 Vacuum Testing of Riser Annulus 56031.9.3 Radiography 560

31.10 Steel Tube Umbilical Risk Analysis and Integrity Management 56131.10.1 Risk Assessment 56131.10.2 Integrity Management Strategy 561

31.11 References 562

Contents xxiii

PART V: Welding and Installation

Chapter 32 Use of High Strength Steel 56532.1 Introduction 56532.2 Review of Usage of High Strength Steel Linepipes 565

32.2.1 Usage of X70 Linepipe 56532.2.2 Usage of X80 Linepipe Onshore 56832.2.3 Grades Above X80 572

32.3 Potential Benefits and Disadvantages of High Strength Steel 57232.3.1 Potential Benefits of High Strength Steels 57232.3.2 Potential Disadvantages of High Strength Steels 575

32.4 Welding of High Strength Linepipe 57632.4.1 Applicability of Standard Welding Techniques 57632.4.2 Field Welding Project Experience 578

32.5 Cathodic Protection 57932.6 Fatigue and Fracture of High Strength Steel 58032.7 Material Property Requirements 581

32.7.1 Material Property Requirement in Circumferential Direction 58132.7.2 Material Property Requirement in Longitudinal Direction 58132.7.3 Comparisons of Material Property Requirements 582

32.8 References 583Chapter 33 Welding and Defect Acceptance 585

33.1 Introduction 58533.2 Weld Repair Analysis 585

33.2.1 Allowable Excavation Lengths for Plastic Collapse 58633.2.2 Allowable Excavation Lengths Using Different Assessments 587

33.3 Allowable Excavation Length Assessment 58933.3.1 Description of Pipeline Being Installed 58933.3.2 Analysis Method 58933.3.3 Analysis Results 591

33.4 Conclusions 59333.5 References 595

Chapter 34 Installation Design 59734.1 Introduction 59734.2 Pipeline Installation Vessels 597

34.2.1 Pipelay Semi-submersibles 59834.2.2 Pipelay Ships and Barges 60234.2.3 Pipelay Reel Ships 60334.2.4 Tow or Pull Vessels 604

34.3 Software OFFPIPE and Code Requirements 60534.3.1 OFFPIPE 60534.3.2 Code Requirements 606

34.4 Physical Background for Installation 60634.4.1 S-lay Method 60634.4.2 Static Configuration 60834.4.3 Curvature in Sagbend 60834.4.4 Hydrostatic Pressure 61034.4.5 Curvature in Overbend 61234.4.6 Strain Concentration and Residual Strain 61234.4.7 Rigid Section in the Pipeline 61334.4.8 Dry Weight/Submerged Weight 61434.4.9 Theoretical Aspects of Pipe Rotation 61634.4.10 Installation Behaviour of Pipe with Residual Curvature 621

34.5 Finite Element Analysis Procedure for Installation of In-line Valves 62434.5.1 Finding Static Configuration 62434.5.2 Pipeline Sliding on Stinger 62634.5.3 Installation of In-line Valve 628

34.6 Two Medium Pipeline Design Concept 628

xxiv Contents

34.6.1 Introduction 62834.6.2 Wall-thickness Design for Three Medium and Two Medium Pipelines 62934.6.3 Implication to Installation, Testing and Operation 63034.6.4 Installing Free Flooding Pipelines 63134.6.5 S-lay vs. J-lay 63234.6.6 Economic Implication 634

34.7 References 636Chapter 35 Route Optimization, Tie-in and Protection 637

35.1 Introduction 63735.2 Pipeline Routing 637

35.2.1 General Principle 63735.2.2 Fabrication, Installation and Operational Cost Considerations 63835.2.3 Route Optimization 638

35.3 Pipeline Tie-ins 63935.3.1 Spoolpieces 63935.3.2 Lateral Pull 63935.3.3 J-tube Pull-in 64135.3.4 Connect and Lay Away 64235.3.5 Stalk-on 642

35.4 Flowline Trenching/Burying 64735.4.1 Jet Sled 64735.4.2 Ploughing 64935.4.3 Mechanical Cutters 649

35.5 Flowline Rockdumping 65335.5.1 Side Dumping 65335.5.2 Fall Pipe 65335.5.3 Bottom Dropping 653

35.6 Equipment Dayrates 65435.7 References 654

Chapter 36 Pipeline Inspection, Maintenance and Repair 65536.1 Operations 655

36.1.1 Operating Philosophy 65536.1.2 Pipeline Security 65536.1.3 Operational Pigging 65736.1.4 Pipeline Shutdown 66036.1.5 Pipeline Depressurization 660

36.2 Inspection by Intelligent Pigging 66136.2.1 General 66136.2.2 Metal Loss Inspection Techniques 66136.2.3 Intelligent Pigs for Purposes other than Metal Loss Detection 668

36.3 Maintenance 67036.3.1 General 67036.3.2 Pipeline Valves 67136.3.3 Pig Traps 67136.3.4 Pipeline Location Markers 671

36.4 Pipeline Repair Methods 67236.4.1 Conventional Repair Methods 67236.4.2 General Maintenance Repair 673

36.5 Deepwater Pipeline Repair 68036.5.1 General 68036.5.2 Diverless Repair Research and Development 68036.5.3 Deepwater Pipeline Repair Philosophy 681

36.6 References 682

PART VI: Integrity ManagementChapter 37 Reliability-based Strength Design of Pipelines 685

37.1 Introduction 685

Contents xxv

37.1.1 General 68537.1.2 Calculation of Failure Probability 685

37.2 Uncertainty Measures 68537.2.1 Selection of Distribution Functions 68637.2.2 Determination of Statistical Values 686

37.3 Calibration of Safety Factors 68637.3.1 General 68637.3.2 Target Reliability Levels 686

37.4 Reliability-based Determination of Corrosion Allowance 68737.4.1 General 68737.4.2 Reliability Model 68837.4.3 Design Examples 68937.4.4 Discussions 69437.4.5 Recommendations 695

37.5 References 695Chapter 38 Corroded Pipelines 697

38.1 Introduction 69738.2 Corrosion Defect Predictions 697

38.2.1 Corrosion Defect Inspection 69738.2.2 Corrosion Defect Growth 69838.2.3 CO2 Corrosion Defects 698

38.3 Remaining Strength of Corroded Pipe 70638.3.1 NG-18 Criterion 70738.3.2 B31G Criterion 70738.3.3 Evaluation of Existing Criteria 70938.3.4 Corrosion Mechanism 70938.3.5 Material Parameters 71238.3.6 Problems Excluded in the B31G Criteria 713

38.4 New Remaining Strength Criteria for Corroded Pipe 71438.4.1 Development of New Criteria 71438.4.2 Evaluation of New Criteria 717

38.5 Reliability-based Design 71738.5.1 Target Failure Probability 71738.5.2 Design Equation and Limit State Function 71838.5.3 Uncertainty 72038.5.4 Safety Level in the B31G Criteria 72138.5.5 Reliability-based Calibration 722

38.6 Re-qualification Example Applications 72338.6.1 Design Basis 72338.6.2 Condition Assessment 72638.6.3 Rehabilitation 731

38.7 References 731Chapter 39 Residual Strength of Dented Pipes with Cracks 733

39.1 Introduction 73339.2 Limit-state based Criteria for Dented Pipe 733

39.2.1 General 73339.2.2 Serviceability Limit-state (Out of Roundness) 73439.2.3 Bursting Criterion for Dented Pipes 73439.2.4 Fracture Criterion for Dented Pipes with Cracks 73539.2.5 Fatigue Criterion for Dented Pipes 73539.2.6 Moment Criterion for Buckling and Collapse of Dented Pipes 736

39.3 Fracture of Pipes with Longitudinal Cracks 73739.3.1 Failure Pressure of Pipes with Longitudinal Cracks 73739.3.2 Burst Pressure of Pipes Containing Combined Dent and Longitudinal Notch 73839.3.3 Burst Strength Criteria 742

39.4 Fracture of Pipes with Circumferential Cracks 74239.4.1 Fracture Condition and Critical Stress 74239.4.2 Material Toughness, Kmat 74339.4.3 Net Section Stress, an 743

xxvi Contents

39.4.4 Maximum Allowable Axial Stress 74339.5 Reliability-based Assessment 743

39.5.1 Design Formats vs. LSF 74339.5.2 Uncertainty Measure 744

39.6 Design Examples 74539.6.1 Case Description 74539.6.2 Parameter Measurements 74539.6.3 Reliability Assessments 74539.6.4 Sensitivity Study 748

39.7 References 749Chapter 40 Integrity Management of Subsea Systems 751

40.1 Introduction 75140.1.1 General 75140.1.2 Risk Analysis Objectives 75140.1.3 Risk Analysis Concepts 75140.1.4 Risk Based Inspection and Integrity Management (RBIM) 752

40.2 Acceptance Criteria 75340.2.1 General 75340.2.2 Risk of Individuals 75340.2.3 Societal Risk 75440.2.4 Environmental Risk 75440.2.5 Financial Risks 755

40.3 Identification of Initiating Events 75640.4 Cause Analysis 756

40.4.1 General 75640.4.2 Fault Tree Analysis 75640.4.3 Event Tree Analysis 757

40.5 Probability of Initiating Events 75740.5.1 General 75740.5.2 HOE Frequency 757

40.6 Causes of Risks 75940.6.1 General 75940.6.2 Is1 Party Individual Risk 76040.6.3 Societal, Environmental and Material Loss Risk 760

40.7 Failure Probability Estimation Based on Qualitative Review and Databases 76140.8 Failure Probability Estimation Based on Structural Reliability Methods 764

40.8.1 General 76440.8.2 Simplified Calculations of Reliability Index and Failure Probability 76440.8.3 Strength/Resistance Models 76540.8.4 Evaluation of Strength Uncertainties 765

40.9 Consequence Analysis 76640.9.1 Consequence Modeling 76640.9.2 Estimation of Failure Consequence 769

40.10 Example 1: Risk Analysis for a Subsea Gas Pipeline 77140.10.1 General 77140.10.2 Gas Releases 77140.10.3 Individual Risk 77340.10.4 Societal Risk 77440.10.5 Environmental Risk 77540.10.6 Risk of Material Loss 77540.10.7 Risk Estimation 776

40.11 Example 2: Dropped Object Risk Analysis 77740.11.1 General 77740.11.2 Acceptable Risk Levels 77740.11.3 Quantitative Cause Analysis 77740.11.4 Results 77940.11.5 Consequence Analysis 781

40.12 Example 3: Example Use of RBIM to Reduce Operation Costs 78140.12.1 General 781

Contents xxvii

40.12.2 Inspection Frequency for Corroded Pipelines 78140.12.3 Examples of Prioritising Tasks 784

40.13 References 785Chapter 41 LCC Modeling as a Decision Making Tool in Pipeline Design 787

41.1 Introduction 78741.1.1 General 78741.1.2 Probabilistic vs. Deterministic LCC Models 78741.1.3 Economic Value Analysis 788

41.2 Initial Cost 78941.2.1 General 78941.2.2 Management 79041.2.3 Design/Engineering Services 79141.2.4 Materials and Fabrication 79241.2.5 Marine Operations 79241.2.6 Operation 792

41.3 Financial Risk 79241.3.1 General 79241.3.2 Probability of Failure 79241.3.3 Consequence 793

41.4 Time Value of Money 79541.5 Fabrication Tolerance Example Using the Life-cycle Cost Model 795

41.5.1 General 79541.5.2 Background 79641.5.3 Step 1-Definition of Structure 79641.5.4 Step 2-Quality Aspect Considered 79641.5.5 Step 3-Failure Modes Considered 79641.5.6 Step 4-Limit State Equations 79641.5.7 Step 5- Definition of Parameters and Variables 79941.5.8 Step 6-Reliability Analysis 80241.5.9 Step 7-Cost of Consequence 80341.5.10 Step 8- Calculation of Expected Costs 80341.5.11 Step 9- Initial Cost 80441.5.12 Step 10-Comparison of Life-cycle Costs 804

41.6 On-Bottom Stability Example 80541.6.1 Introduction 80541.6.2 Step 1-Definition of System 80541.6.3 Step 2- Quality Aspects Considered 80541.6.4 Step 3- Failure Modes 80541.6.5 Step 4- Limit State Equations 80641.6.6 Step 5-Definition of Variables and Parameters 80641.6.7 Step 6- Reliability Analysis 80641.6.8 Step 7- Cost of Consequence 80641.6.9 Step 8- Expected Cost 80641.6.10 Step 9- Initial Cost 80741.6.11 Step 10- Comparison of Life-cycle Cost 807

41.7 References 807

SUBJECT INDEX 809