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Subsea PipelinesAnchor Damage Assessment and Repair

A O i f M th d d Li it tiAn Overview of Methods and Limitations With A Case Study From the BP CATS

Pipeline

Roland Palmer-Jones

Penspen Ltd 2010

r.palmer-jones@penspen.comPenspen Integrity, UK

SUBSEA EUROPE 2010 Paris

Outline

Challenges Safety pressure reductions Assessment Stages Typical Damage Inspection Options/Limitations Assessment Methods/Limitations Repair Options

Penspen Ltd 2010

Case Study

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Pipeline Damage - Challenges

Ensure Safety M i t i O ti Maintain Operation

Prevent Failure Shutdown only if required

Select the Right Repair Contain pressure Support structure

Repair Quickly

Defect Identification, Measurement and Assessment

Emergency Repair System

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Repair Permanentlyg y p y

Safety!

Industry Practice - Reduce Pressure Prevent Rupture 1.2

h

Prevent time dependent failure

Will Pipe Collapse? Bending Ovalisation Denting External pressure

Can Pressure be Reduced?

0.2

0.4

0.6

0.8

1

Failu

re S

tres

s/Yi

eld

Stre

ngth

leak

rupture

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Can Pressure be Reduced? Hydrostatic head Phase change

Even Basic Pressure Reduction Decision Requires Defect + Risk Assessment

00 1 2 3 4 5 6 7 8

Normalised Defect Length

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Outline

Challenges Safety pressure reductions

A t StAssessment Stages Typical Damage Inspection Options/Limitations Assessment Methods/Limitations Repair Options

Penspen Ltd 2010

Case Study

Defect Assessment - Stages

Incident Reported Preliminary assessment

ROV + Sonar Survey Secondary assessment

Detailed Diver/ROV Survey Main assessment

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Preliminary Assessment - Questions

Incident ReportedShi i Ship reports snagging

ILI report indicates dent and gouge

Sonar/ROV survey indicates damage

Preliminary Assessment Questions Should the pipeline be shutdown?

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Is a pressure reduction required? Is it safe for a vessel to approach? Will a repair be needed? What type of repair is likely?

Preliminary Assessment - Data Incident details

Location, Ship speed,Ship speed, Was anchor abandoned on Pipeline? Did anchor chain break? Leak?

Ship details Tonnage, Anchor size/weight, Anchor chain weight/breaking strain.

Pipeline details

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Pipeline details Diameter, Wall thickness, Material, Coatings, Depth of burial, Operating pressure.

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Preliminary Assessment - Approach

Calculate Damage Resistance Dent Depth vs Impact Energy

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2 De-burial vs Ship kinetic energy Bending vs Ship kinetic energy

Calculate Available Energy for Damage Anchor + chain weight and velocity

Concrete crushing Local denting

Ed 2 100 m p

OD

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Local denting Ship mass and velocity

Pipeline de-burial Global deformation/bending

Preliminary Assessment - Potential Conclusions

Significant damage not credible (Small ship + Large pipeline)pipeline) No immediate pressure reduction Proceed with ROV survey Review repair readiness

Significant damage possible (Large ship + Large pipeline) Reduce pressure Mobilise emergency repair system (grouted sleeve)

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Mobilise emergency repair system (grouted sleeve) Proceed with ROV

Significant damage likely (Large ship + Small pipeline) Shutdown or significantly reduce pressure Mobilise emergency repair (mechanical connectors) Proceed with ROV

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ROV + Sonar Survey

Initial survey to: Confirm location Provide general visual information

ROV Video survey

De-burial Displacement Coating state Evidence of denting Evidence of gouging

Currents

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Cu e ts Sediment/silt Basic measurements CP stab identify bare metal

Sonar Displacement Seabed scars

Secondary Assessment- Questions

Should the pipeline be shutdown?shutdown?

Is a pressure reduction required? Is it safe for divers? Can the anchor be safely

removed? Can excavation / exposure be

carried out?

Penspen Ltd 2010

carried out? Can the coating be removed? Will a repair be needed? What type of repair is likely?

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Secondary Assessment

Global Stress analysis of snagging/displacement to

l t t diti

Tension

B di Bending

As-laid Pipeline

Displaced Pipeline

evaluate stress condition Span assessment Stability Identify likely local damage

type: Plain dent Dent on weld

CompressionBending Bending

Direction of Anchor Impact & Drag

Axial defect (fixed width, 20mm), axial compression, internal pressure (55 bar) DNV

-270 1.0mm Defect Depth2.0mm3.0mm

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Dent on weld Dent plus gouge Gouge only

Calculate critical damage sizes Identifies measurements

required

-260

-250

-240

-230

-220

-2100 100 200 300 400 500 600 700 800 900 1000

Axial Defect Length 2c (mm)

'saf

e' a

llow

able

tota

l axi

al c

ompr

essi

on (M

Pa)

4.0mm5.0mm6.0mm7.0mm8.0mm

Diver Survey

Excavate Remove coating D t il d i l i ti Detailed visual inspection Geometric inspection Magnetic Particle

Inspection Ultrasonic inspection

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Ultrasonic inspection

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Final Assessment- Questions

Should the pipeline be shutdown? Is a pressure reduction required? Will a repair be needed? What type of repair?

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Final Assessment

Assess local damage Burst pressure

Oil Pipeline Pressure history

800

1000

1200

1400

ure

(psi

)

Burst pressure Fatigue life Operational restrictions

Basis of assessment Industry guidance/experience FEA

0

200

400

600

22-Mar 23-Mar 24-Mar 25-Mar 26-Mar 27-Mar 28-Mar 29-Mar 30-Mar 31-Mar 01-Apr 02-Apr

Time

Pres

su

Penspen Ltd 2010

Include effects of displacement

Damage behaviour and failure mechanism Repair performance requirements

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Outline

Challenges Safety pressure reductions Assessment Stages Assessment Stages

Typical Damage Inspection Options/LimitationsAssessment Methods/Limitations

R i O ti

Penspen Ltd 2010

Repair Options Case Study

Typical (Possible) Damage

Rupture Gouge Displacement Plain Dent Dent Plus Displacement

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Dent on Weld Dent and Gouge Kinked Dent

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Inspection Options and Limitations

Sonar Survey ROV

Vi l Visual Position CP

Diver Visual Calliper

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Straight edge MPI UT Laser scanning

Assessment Options and Limitations

Gouge NG18 Displacement FEA or Beam

Theory (strain limits) ddt

dd

c

c

f

11

1

Theory (strain limits) Plain Dent Empirical limits, strain

assessment, EPRG fatigue model Dent Plus Displacement No

proven methods Dent on Weld EPRG fatigue

model

Mt1

2

501000

101

292.4

sA

U

KN

Penspen Ltd 2010

Dent and Gouge EPRG model Kinked Dent No Proven method

2

12

02

012

1 )ln(exp2

2.1028.115.1expcos2

KKC

RD

tRY

RDY

AdE vf

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Offshore Pipeline Repair Options

Grinding Clamps / Sleeves Section

Replacement Connectors Hyperbaric welding Recovery to

Penspen Ltd 2010

Recovery to surface

Outline

Challenges Safety pressure reductions Assessment Stages Assessment Stages Typical Damage Inspection Options/Limitations Assessment Methods/Limitations

Repair Options

Penspen Ltd 2010

Case Study

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Grind repair

Area to be removed

Pipe

Cracking

Hardened layer

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Clamps / Sleeves

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Section Replacement

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Outline

Challenges Safety pressure reductions Assessment Stages Assessment Stages Typical Damage Inspection Options/Limitations Assessment Methods/Limitations Repair Options

Penspen Ltd 2010

Case Study

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Central Area Transmission System (CATS)

Penspen Ltd 2010

Details of the Incident

Late evening on 25th June 2007 a large crude tanker which had been anchored to the north of the CATS Pipeline for a period of time awaiting entry to Teessport Harbour, began to drag its anchor in deteriorating weather

At approx. 2330 the vessel reported that it had snagged its anchor on a pipeline to the south east of its original position

After around 10 minutes the vessel was able to free itself from the pipeline and move off to the south

Harbour Authority reported incident to CATS Terminal staff BP Emergency Response Plans instigated & investigation

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commenced Incident has been fully investigated by Marine Accident

Investigation Branch & the report has recently been published (Report No. 3/2008 at www.maib.gov.uk)

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Anchor Damage Case Study

25th June 2007 - A ship was in difficulty in bad weather.

O f it h hit th 36Anchor Weight circa

14t

One of its anchors hit the 36 pipeline and lifted it from under the seabed

Harbour Authority reported

Penspen Ltd 2010

Harbour Authority reported incident to CATS Terminal staff

BP Emergency Response Plans instigated & investigation commenced

Initial Assessment

No evidence of rupture No evidence of leak Potentially severe damage Small pressure reduction imposed Pressure controlled

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Anchor weight and velocity approx. 15 mm dent (1,7%)

Gouging? Displacement? Bending?

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ROV Survey

Initial reports showed concrete damage, bending,damage, bending, gouging, and denting

Penspen Ltd 2010

Secondary Assessment

Apparently severe damage Dent gouge calculations indicate

failure pressure below design for credible combinations.

P d ti i d

Penspen Ltd 2010

Pressure reduction requiredReview repair options

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Investigation of Repair options

BP Project Team established & dedicated to the repair.

Do nothing or dress defect, assess and leave

following repair options reviewed in parallel with inspection activities

Penspen Ltd 2010

Wet weld, metal build up Deploy existing BP clamp / identify alternatives across the globe Replace section with subsea connectors Replace section with hyperbaric welds Lift pipe and re-lay section with lay barge and tie-in Re-lay new section with lay barge and tie-in

Detailed Inspection / Work Program

1. Pipeline depressurisation (in controlled stages from 113 barg to 54 barg) to enable safe diver access

2. Diverless excavation of pipeline and further ROV inspection2. Diverless excavation of pipeline and further ROV inspection 3. Final excavation of pipe spool (approx. 20m)4. Concrete & Coal Tar Coating removal (approx. 14m)5. Detailed Diver Inspection

- Close visual inspection- Out of Straightness survey- Ovality Survey- Taut Wire

Penspen Ltd 2010

- Magnetic Particle Inspection (welds & defect areas)- Ultrasonic Inspection (welds & defect areas) automated and manual

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Inspection Results

1.5m vertical displacement

4.5m horizontal displacement

Damage over a 4m length in middle Damage over a 4m length in middle of spool

2 Dents within a larger deformed area

Penspen Ltd 2010

2 Dents within a larger deformed area

31mm and 25mm max. depth (3.4%D)

2 Protrusions of max. 15mm

Weld deformed

No weld defects / cracking

No gouging

Final Defect Assessment Defects were assessed using

the Pipeline Defect Assessment Manual (PDAM)

Limitations: No method for combined No method for combined

dent and external load. Limited test data for large

diameter offshore pipelines. FEA of displacement. FEA of dented area EPRG dent fatigue Terminal Inlet Pressure (Previous 12 Months)

123

125

Penspen Ltd 2010

105

107

109

111

113

115

117

119

121

Time

Pres

sure

(bar

)

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Results of Defect Assessment

Analysis Findings: No reduction in static strength of pipeline Fatigue life of pipeline reduced by dents on weld

Repair Decision: Existing sleeve would not fit (too short and pipe bent) Structural, cement grouted sleeve repair selected to

provide reinforcement of dented area

Penspen Ltd 2010

How long did it take?

Incident occurred - 25 June Initial survey complete 30 June Pipeline shutdown 1 July Pipeline shutdown 1 July Pipe depressurised and safe to dive 18 July Detailed inspection complete 28 July Go ahead for sleeve fabrication 29 July Sleeve Fabrication / Fit-Up Trials complete - 17 August Diving Support Vessel on location - 18 August Pipeline recommissioning commenced - 24 August

Penspen Ltd 2010

p g g Delivery of on-spec gas - 1 Sept Rock dump complete 2 Oct

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Cross-industry support to release vessels during peak summerperiod both from operators and contractors

Fantastic support & dedication from key contractors with whomBP already had long term relationships Technip Acergy RBG

Critical Success Factors

BP already had long term relationships Technip, Acergy, RBG,JP Kenny, Penspen/APA, Jee, Foundocean, Subsea 7 andothers

Rapid mobilization of dedicated project team from BP &contractors

Existing relations with BP global experts simplified assuranceprocesses

Clear accountabilities within Project Team Pipeline Integrity,Subsea Activities Terminal Ops Sleeve Fabrication JV and

Penspen Ltd 2010

Subsea Activities, Terminal Ops, Sleeve Fabrication, JV andReputation Management

Strong engagement with regulators from Day 1

HIGH QUALITY, PERMANENT PIPELINE REPAIR SAFELY IMPLEMENTED IN LESS THAN 3

MONTHS

Summary There are stages to damage assessment Uncertainties at each stage Data changes Need to use all available data Specialist skills/experience needed Contingency plans/repairs may not be appropriate Proven methods for assessment may not be available Caution is needed

Penspen Ltd 2010

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Repair Management

Pipeline operator Vessel operator Diving contractor ROV operator ROV operator NDT contractor Defect specialists Welding Re-commissioning Subsea designer Verification agency/consultant Equipment suppliers

Pipe handling

Penspen Ltd 2010

Pipe handling Concrete removal Pipe cutting Clamp or connectors Welding habitat Isolation tools De-watering pigs

Regulator

REPAIR: Caution.

Some wise words on repair*: Do no harm!

A bad repair can makeA bad repair can make matters worse.

Repairs need careful engineering, at least as much as a new construction.

Do not act in haste. A repair is often not a good time to try

something new.

Penspen Ltd 2010

g There is less experience with a new procedure,

compared to tried and tested designs. Surprises may occur with uncertainty and incompletely planned engineering

*A C Palmer, R King, Subsea Pipeline Engineering, Penwell. 2004.