DMFT2014, Zhuhai China

Transcription

1 OIL & GAS DMFT2014, Zhuhai China 深水管道管道设计设计及安装的风险和挑战 Risks and Challenges of Deepwater Pipeline Design and Installation Edwardus NG, BD Manager O&G Asia Pacific 19th October SAFER, SMARTER, GREENER

2 DNV GL -A new company with 150 years of experience DNV and GL Noble Denton joined forces in September We ve drawn upon our proud heritages to create: Greater and deeper technical expertise Extended global reach Four Business Areas ( Rev 3 Bn USD) 16,000 employees in 300 offices (China 1,200 employees) 5% of revenue committed to R&D annually (150 MSUD) 2

3 Deepwater Pipelines in unchartered territories Objectives of Presentation Present some key risks and challenges when designing and installing deepwater pipelines Recommend possible approach and solutions to overcome these risks and challenges (based on OS-F101) Year (DW) Global Offshore O&G Supply from deepwater % % 3

4 Some Deepwater Pipeline Projects (designed to DNVGL-OS-F101) RIL KG-D6 Bluestream Ormen Lange Water Size Length Project depth No. Completed (m) (in) (km) Blue Stream Ormen Lange KG-D South Stream ongoing South Stream 4

5 Risks and Challenges Deepwater pipelines Some key Risks and Challenges are: 1. Wall thickness design 2. Installation challenges 3. Flow Assurance - Prevention of Hydrates 4. System pressure test 5. Geohazards 6. Repair systems for ultra-deep waters 5

6 Deepwater challenge #1 Pipeline collapse Wall thickness design Risks and Challenges: High external pressure means pipeline collapse failure mode governs wall thickness design rather than pressure containment buckling vs yielding Manufacturing of thick wall pipes may limit project options and project feasibility. Can they be produced? Can the pipeline be laid? Project viability often depends on having an optimal wall thickness which provides adequate strength, can be manufactured and installed at an acceptable cost. Solutions: Use of limit state design approach to optimize wall thickness design e.g. OS-F101 standards Specify improved linepipe properties against collapse failure by improving compressive yield strength, balance between strength and toughness and improving linepipe roundness Justify use of less conservative safety factors through technology qualification 6

7 Limit State Design approach to optimise wall thickness DNVGL-OS-F101 Submarine Pipeline Standards: Sect 5 Design 7

8 Deepwater challenge #1 Pipeline collapse Wall thickness design Risks and Challenges: High external pressure means pipeline collapse failure mode governs wall thickness design rather than pressure containment Manufacturing of thick wall pipes may limit project options and project feasibility. Solutions: Use of limit state design approach to optimize wall thickness design e.g. OS-F101 standards Specify improved linepipe properties against collapse failure by improving compressive yield strength, balance between strength and toughness and improving linepipe roundness Justify use of less conservative safety factors through technology qualification 8

9 Enhancing Collapse Capacity of UOE Pipes Thick wall designs > 50mm is on the border of the capacity for linepipe manufacturing industry Pipe manufacturing process (UOE) reduces compressive yield strength by15% (Ref: DNVGL- OS-F101) U-ing and O-ing Stress Expansion Studies have shown that the strength can be restored by light heat treatment e.g. during application of external coating Strain DNVGL has been involved in a technology qualification project with the aim of utilising this in design Focus on ovality caused by manufacture process (pipe forming) Collapse Compressive yield strength reduction due to Bauschinger effect 9

10 Collapse capacity of pipelines design requirements DNVGL-OS-F101 Submarine Pipeline Standards: Sect 5 Design 10

11 Collapse buckling capacity (D/t) vs water depth Validity range: D/t = 15-45

12 Risk and Challenges Deepwater pipelines 1. Wall thickness design 2. Installation challenges 3. Flow Assurance - Prevention of Hydrates 4. System pressure test 5. Geohazards 6. Repair systems for ultra-deep waters 12

13 Deepwater challenge #2 Installation Installation Risks and Challenges: High strains coupled with high external water pressure with increased risks of local buckling and fracture High pipelay vessel tensioner capacity required. More stringent requirements to tensioner holding Seven Borealis courtesy of Subsea7 Ability to detect buckle and repair a wet buckle Solutions: Use of limit state design approach to check against local buckling, ovalisation and to optimize wall thickness/ pipe weight Specify supplementary linepipe material properties for high strains and additional testing Specify supplementary dimensional properties of the linepipes Use of Engineering Criticality Assessments for girth weld assessments Self propelled buckle detector crawlers with remote sensors (e.g. microwave buckle detector used on S7000) Courtesy: Saipem 13

14 Enhanced material and dimensional properties for fracture and buckling control DNVGL-OS-F101 Submarine Pipeline Standards (2013) : Sect 7 14

15 Risks and Challenges Deepwater pipelines 1. Wall thickness design 2. Installation challenges 3. Flow Assurance Prevention of Hydrates 4. System pressure test 5. Geo-hazards 6. Repair systems for ultra-deep waters 15

16 Deepwater Challenge #3 Hydrate plugs Formation of Hydrate plugs Risks and Challenges: In the event of a small leakage, seawater ingress into a deepwater gas pipeline (external pressure > internal pressure) can lead to formation of hydrates. Large Hydrate plugs may form How large? How to intervene? Solutions: Passive prevention systems Insulation (coating, PiP, bundle) Trenching Parallel trenched pipelines Active prevention systems Injection of methanol/glycol (MEG) Heating electrical, circulation of hot water Dehydration of pipeline Reactive - Hydrate remediation Depressurisation Injection of methanol/glycol (MEG) Heating Fluid Pressure (MPa) Source: Hydrate dissociation curves Increasing MEG injection 0 Temperature (C) Example of a Hydrate formation curve 16

17 Risks and Challenges Deepwater pipelines 1. Wall thickness design 2. Installation challenges 3. Flow-Assurance Prevention of Hydrate plugs 4. System pressure test 5. Geohazards 6. Repair systems for ultra-deep waters 17

18 Deepwater Challenge #4 Relevance of system pressure test System Pressure Testing Risks and Challenges: Most pipeline codes requires field pressure testing after installation to 1.1 to 1.25 times design pressure. Where the external pressure is much larger than the internal pressure, is this test relevant and practical? The system test pressure may cause lateral buckling of the pipeline. Require huge compressors to empty the pipeline. Solution: Adopt DNVGL-OS-F101 provisions for system pressure test waiver (Sec.5 B203) 18

19 Waiver for System Pressure Test (DNVGL-OS-F101) DNVGL-OS-F101 Submarine Pipeline Standards (2013) : Sect 5 19

20 Risks and Challenges Deepwater pipelines 1. Wall thickness design 2. Installation challenges 3. Flow-Assurance Prevention of Hydrate plugs 4. System pressure test 5. Geohazards 6. Repair systems for ultra-deep waters 20

21 Deepwater challenge #5 Geohazards Geohazards Risks and Challenges: Steep slopes Loose Sediments Slope instabilities and mudslides Turbidity flow Seismic activities Turbidity current Earthquake causing seabed faults Uneven seabed causing long freespans Lack of suitable methods for seabed intervention Solutions: Adequate characterization of seabed and geomorphology Optimise routing of pipeline considering potential hazards, safety, minimise pre and post lay intervention Apply advanced analyses and design where hazards cannot be avoided. 21

22 Some challenges of deepwater and complex seabed CONFIDENTIAL Confidential 22

23 Deepwater challenge Geohazards DNVGL-OS-F101 Submarine Pipeline Standards (2013) : Sect 3 Seismic hazard Soil & seabed characterisation Slope stability Pipeline integrity See also Sec. 3 C700 Seabed Properties Mass gravity flows 23

24 Freespan assessment based on DNVGL-RP-F105 Long freespan Multi-mode response Advanced assessment of long freespans with multi-mode response can result in substantial cost saving in seabed intervention. 24

25 Risks and Challenges Deepwater pipelines 1. Wall thickness design 2. Installation challenges 3. Flow-Assurance Prevention of Hydrate plugs 4. System pressure test 5. Geohazards 6. Damage and Repairs 25

26 Deepwater challenge #6 Repairs Damage and Repairs Risks and Challenges: Wet buckle during installation Damage during operation Ingress of seawater/ hydrate plugs Unsuitable soil/ environmental conditions Lack of diverless repair systems for ultra deepwater Solutions: Emergency response procedures must be established Develop and qualify repair methods suitable for specific pipeline system and environmental conditions 26

27 Deepwater challenge Repairs DNVGL-RP-F113: Ch. 1 27

28 Conclusion Presented some of the key risks and challenges of deepwater pipelines. 1. Wall thickness design 2. Installation challenges 3. Flow Assurance - Prevention of Hydrates 4. System pressure test 5. Geohazards 6. Repair systems for ultra-deep waters These can be mitigated by: Use of appropriate standards, specifications and recommended practices for deepwater applications Using Limit State design approach to optimise design Comprehensive geotechnical and environmental investigations to reduce uncertainties with Loads; Specify enhanced/ supplementary properties of linepipe Address installation, testing and operational challenges at the design stage to improve layability, reliability and to minimise subsea intervention; Close surveillance during manufacturing, installation and testing to ensure design conditions and assumptions are met. 28

29 谢谢 Edwardus Ng Business Development Manager, DNVGL Oil & Gas Asia Pacific SAFER, SMARTER, GREENER 29