Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity

Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity by Kaushik Mukherjee Principal Engineer – Civil & Structural, UTS, GTS PETRONAS Prefabrication & Modular Construction Shanghai, China 14th May, 2014 © 2013 PETROLIAM NASIONAL BERHAD (PETRONAS) All rights reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the permission of the copyright owner.

CONTENTS…… • Overall Structural Integrity Management of the Old Assets • Performance Based Design for New Construction • General Fabrication and Installation Flaws • Data Gathering and Assessment Process for Older Structures • Mitigation Plan, RBI and Maintenance

Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Contents; Kaushik Mukherjee;

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Overall Structural Integrity Management of the Old Assets

Malaysian Offshore Structures

Upstream Activities • Types of platform range: Drilling, wellhead, production, gas compression, living • >175 fixed offshore platforms in Malaysia • Operations focus on PMO, SKO and SBO regions quarter, vent and riser • Majority of these structures have exceeded Design lives Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Overall Structural Integrity Management of the Old Assets; Kaushik Mukherjee;

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Requirement For Requalification • Damage by major hurricanes elsewhere GOM (e.g. GOM, North Sea etc.) pointed out some of the offshore assets (offshore jackets) in these areas may not meet today requirements for safety and reliability. • Deterioration of structures assets and modification on functionality while in services and stringent standards based on new knowledge. • Regulatory to consider the need to assess the ability of existing assets to perform original function and accommodate new requirement while in service. sophisticated and rational • More requalification procedures to ensure the safety of these assets to continue in service. Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Overall Structural Integrity Management of the Old Assets; Kaushik Mukherjee;

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Asset Integrity Management (AIM) • Managing the Integrity of the existing assets is through Corporate AIM initiatives. Objective of AIM is to ensure the asset is able to perform its required function effectively and efficiently whilst protecting health, safety and environment (HSE), asset and business reputation through risk based management for the asset lifecycle. • AIMs covering all assets e.g. Mechanical, electrical, instrumentation, Structural, pipeline and etc. • Structural Integrity Management (SIM) processes and SIM System (SIMs) had been implemented for offshore jackets structures

Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Overall Structural Integrity Management of the Old Assets; Kaushik Mukherjee;

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Asset Integrity Management (AIM)

AIMS Life Cycle Model Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Overall Structural Integrity Management of the Old Assets; Kaushik Mukherjee;

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SIM Requalification Processes

• Data: Assemble data on the structure, its history and exposure level • Evaluation: Determine if any assessment initiators are triggered • Inspection Strategy: Identify Inspection requirement • Action Program: Apply Prevention and Mitigation Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Overall Structural Integrity Management of the Old Assets; Kaushik Mukherjee;

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Performance Based Design for New Construction

Performance-Based Design (PBD)

Ref.: Document Number WW ALL E 04 009, Rev. 0, 2011; Performance Based Design Guideline

 Integration of Operational & Maintenance Philosophy  Conglomeration of Lessons Learned & Best Practices for the Region

Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Performance Based Design for New Construction; Kaushik Mukherjee;

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Performance-Based Design (PBD)  Design of Structures that have got Predictable Performance in Compliance with Performance Goals

 The Selection of Performance Objectives or Target Reliability  Understanding of the Enabling Technology  The Process by which the Additional Project Risks Associated with the PBD Solutions can be Understood and Managed  Component Based Design vs System Based [Performance]

   

Importance of Initial Design to Reduce OPEX & Risk Through Life-Cycle Advantage of Load Redistribution, Robustness Impose Ductility Check to Ensure Absorption of Excessive Energy Selection of type of Foundation, No. of Legs, Grout, Framing, Slenderness, Joint Strength


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Performance-Based Design (PBD)  Modelling & Analysis Accuracy [Courtesy McDermott, Singapore]

Jacket Loadout

Jacket Launch

Jacket Floatover


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General Fabrication and Installation Flaws

Weld-on-Weld

Main Vertical Column supporting Main Deck Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity General Fabrication and Installation Flaws; Kaushik Mukherjee;

Page 14

Weld-on-Weld

Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity General Fabrication and Installation Flaws; Kaushik Mukherjee;

Page 15

Weld-on-Weld

Brace mark Long Seam


Page 16

Offshore Welding


Page 17

Offshore Welding


Page 18

Offshore Welding


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Data Gathering and Assessment Process for Older Structures

What triggers Re-assessment ? Based on Anomalies: Time Driven Anomalies

Event Driven Anomalies

Corrosion

Code & Regulations

Fatigue

Environmental Loading

Scour

Modifications/Additions

Subsidence

Boat Collision/Drop Object/Vibration

Marine Growth

Shallow Gas Exposure Earthquake Fire / Blast Exposure Level

Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Data Gathering and Assessment Process for Older Structures; Kaushik Mukherjee;

Page 21

What trigger Re-assessment ? o Modification/Alteration/ Addition

Boat Impact

Shallow Gas

Corrosion Fire/blast Earthquake Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Data Gathering and Assessment Process for Older Structures; Kaushik Mukherjee;

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Re-assessment Processes • When installation reaches an age where requalification is necessary there are no industry or government guidelines on when platform may require requalification.


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Risk Ranking Assessment  Establishment of LOF and COF risk matrix.  Establishment of LOF is Rule Based.  COF adopt semi-quantitative Rule for Life Safety, Economic & Environment LOF Procedure


Page 24

Risk Ranking Assessment COF Procedure


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Risk Ranking Assessment Quantitative

Design

P -RBI

RSR

PoF

3-4 Legs UnGrouted K-Braced Low Deck Pre-RP2A

> 640

RSR <= 1.0

1E-2 > PoF

4-6 Legs UnGrouted VD-Braced 2ft Air Gap Post-RP2A

480 < Score <= 640

1.4 > RSR <= 1.0

1E-2 > POF <= 1E- 3

6-8 Legs UnGrouted VD-Braced 5ft Air GAp Post-RP2A

320 < Score <= 480

1.8 > RSR <= 1.4

1E-3 > POF <= 1E- 4

4 Legs UnGrouted X-Braced 5ft Air Gap Post-RP2A

160 < Score <= 320

2.2 > RSR <= 1.8

1E-4 > POF <= 1E- 5

6 Legs X-Braced Grouted 5ft Air Gap Modern-RP2A

Score <= 160

RSR >= 2.2

POF < 1E-5

L ik e lih o o d o f F a ilu r e

Qualitative

5

M

H

H

VH

VH

4

L

M

H

H

VH

3

L

L

M

H

H

2

VL

L

L

M

H

1

VL

VL

L

L

M

A

B

C

D

E

Consequence of Failure

Slight Leak 1-50 boe

Minor Leak 50-500 boe

Localised Leak 50-500 boe

Major Leak > 50,000 boe

Catastrophic Leak > 50,000 boe

Environmental

Very Low < US$6MM

Low US$6MM- US$45MM

Medium US$45MM-US$75MM

High US$75MM- US$100mm

Very High > US$100MM

Business

Very Low < 10-5

Low <= 10-5 - < 10-4

Medium <= 10-4 - < 10-3

High <= 10-3 - < 10-2

Very High >= 10-2

Life Safety


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Risk Ranking Assessment [Example]


Page 27

Risk Ranking Assessment [Example]


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Design Level Assessment  In-place Elastic Analysis – Component Based Assessment  Extreme Condition only (100 years RP waves)  Acceptance Criteria – UDC and Foundation Safety Factor as per Code requirement (API WSD or LRFD)


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Ultimate Strength Assessment  System based Assessments - Push Over Analysis, Member Importance and Reliability Assessment  Acceptance Criteria – POF values: ISO Requirements – For existing Structures = in Malaysian waters – Manned Structures =10,000 years and un-manned = 1,000 years RP waves (translated to RSR = 1.5 for manned and 1.32 for unmanned structures [Hazard Curves]

2.0

4 3

1.8

2

Global Load Factor

1.6 1.4

1

1.2 1.0 0.8 0.6 0.4 0.2 0.0 0.0

3.0

6.0

9.0

12.0

15.0

Global Displacement (ft)


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Ultimate Strength Assessment End-on Direction 18000

Plastic hinges on all legs just below EL (-)120' and on all VD members on Face A & B between EL(-)284' and EL(-)120'

Plastic hinge on VD member on Face B from EL(-) 194' to EL (-)120' on Leg A3; 20,000-year return wave

16000

Platform collapse, 60,000-year return wave, base shear 14,519 kips, Hmax=82.7 ft Buckling of VD member on Face B from EL (-)194' to EL (-)120' on Leg A3; 12,000-year return wave

14000

First member failure, 20,000-year, base shear 13,196 kips, Hmax=77.6 ft

10,000-year return wave base shear 12,286 kips, Hmax=74.5 ft Approximate Elastic Limit 600-year return wave

10000

1,000-year return wave base shear 9,275 kips, Hmax=64.3 ft

8000

400-year return wave crest reaches cellar deck B.O.S. Base shear 8,090 kips, Hmax=60.0 ft

4000

B

N O

3

G

N

2

D IA

1

AL

100-year return wave base shear 6,775 kips, Hmax=53.8 ft

6000

BROADSIDE

Environmental Load (kips)

12000

END-ON

2000 A

KEY PLAN & PUSHOVER DIRECTIONS

0 0

1

2

3

4

5

6

7

8

Deck Deflection (ft)


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Ultimate Strength Assessment


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Ultimate Strength Assessment E (270°) 15.0 NE (315°)

SE (225°)

10.0 5.0

N (0°)

S (180°)

0.0

NW (45°)

SW (135°) W (90°)

RSR

Total Base Shear

Wave height

Global Load

Member Importance Analysis Criteria: 1. Fatigue members (as indicated in the Spectral Fatigue report) 2. Members prompted to boat impact 3. First yield members 4. Reported Anomalies, e.g., Cracks, FMD etc. 4 3 2 1 0

-1 0.0

0.5

1.0

1.5

Global Displacement


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Reliability Assessment Load Surfaces Hs 4.25 3.75 3.25 2.75 2.25 1.75 1.25 0.75 0.25

0.5

1.5

10 10

0 0

2.5

3.5

4.5

5.5

6.5

2 1 9 11 37 6 63 84 2 52 109 101 16 65 76 54 18 123 260 287

1 2 9 28 44 57 34 175

7.5

1 3 12 17 21 17 71

8.5

1 3 6 7 9 26

Tz 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5

1 2 3 5 11

1 2 3 6

1 2 3

1 2 3

1 1 2

1 1

1 1

0

0

0 0 1 5 23 92 223 357 296 0 997

0

Calculated Reliability Response surfaces

Loading

R

Derived reliability β Safe : G ≥ 0

Failure : G < 0 β G=0

S

R2+S2 = constant Hs 4.25 3.75 3.25 2.75 2.25 1.75 1.25 0.75 0.25

0.5

10 10

1.5

0 0

2.5

3.5

4.5

1 11 6 63 2 52 109 16 65 76 18 123 260

5.5

6.5

7.5

1 2 2 9 9 37 28 84 44 101 57 54 34 287 175

1 3 12 17 21 17 71

8.5

1 3 6 7 9 26

Tz 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5

1 2 3 5 11

1 2 3 6

1 2 3

1 2 3

1 1

1 1 2

1 1

0

0

0

0 0 1 5 23 92 223 357 296 0 997

Resistance Surfaces

Hazard Curve Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Data Gathering and Assessment Process for Older Structures; Kaushik Mukherjee;

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Case Study: Platform A with Major Anamolies Anomalies  3 nos. of visual cracks  3 joints with laminar tearing  9 flooded members


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Case Study: Anomalies

Visual crack at WN52 from 9o/c to 12o/c

Visual crack at WN52 from 12o/c to 3o/c


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Case Study: Risk Assessment

Risk Ranking = 5B (High Risk) Design Level Analysis – capture the linear elastic response of the structure under static loading conditions

Unity Check (Applied/Allowance < 1.0)


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Case Study: Ultimate Strength Assessment Modelling

A complete model consisting of the structure, environment, pile and soil Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Data Gathering and Assessment Process for Older Structures; Kaushik Mukherjee;

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Case Study: RSR & Failure Mechanism


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Case Study – Joints Results

Objective: Examine the capacity of the lamination joints prior to total collapse.


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Case Study: Conclusion 

The lowest RSR is 1.72 for West direction (60˚); The collapse mechanisms = buckling of leg followed by lateral soil failure. Under current anomalies, the structure still having adequate strength to fulfill global integrity requirement for service.



The existing cracks and laminated issue do not impact the overall structure strength even when most of the joints have failed before the collapse of the structure.



The structure has adequate redundancy to redistribute the load to other load path (adjacent member).



Strengthening of the joints is therefore not required, only require continuous monitoring of the cracks through inspection activities.


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Case Study 2: Platform B  Requalification of structures due to Shallow Gas effect.  Sensitivity Analysis of soil parameters (Soil Capacity)  Load Response Surfaces (Environmental Loading)  Ultimate Strength Assessment (RSR)

V

H

Environment Wave height, current and wind speed Load-effect Model uncertainty in the calculated environmental loadeffect Soil Conditions Intercept value of static, undrained, soil shear strength Cyclic loading factor Soil strain at 50% strength Excess pore pressure Capacity

Relative importance (%) 86

M

Crater

 First order reliability Methods (POF) Description

Exposed pile

Reduced skin friction

Symbol in Proban input Hrx, Ucurr, Vwnd

7

U_L

1 ∼0 ∼0 2 3

Su0 Ucy eps50 Xpp

Pressure confine zone Shallow gas seepage

Model uncertainty factor on the calculated capacity


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Case Study 2: RSR Assessment & Findings

Variable

Distribution type

Mean value

Standard deviation

Su Su Ucy ε50

Fixed Normal Normal Normal Normal

12.2+1.93z (kPa) 12.2+1.93z (kPa) 0.9 1.15% -33.2+2.22z (kPa)

N/A 6.0 kPa * 0.09 0.174% * 50.4 kPa

DU **


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USFOS Animation to Failure


44

USFOS Animation to Failure


45

Mitigation Plan, RBI and Maintenance

SIM Inspection and Mitigation • Requalification analysis – provide guidance on the inspection required • Considerable pressures to reduce inspection – constitute 40% of the cost • No industry standards for minimum inspection required • Inspection schemes – differs from operator to operator (API RP2A provide some guidance on level of inspections) • The level of inspection also depends on: the type of environment , manned or unmanned, Economic Consequences of loss and Regulatory/Company requirements • Mitigation option based on ALARP principles (if required after comprehensive requalification analysis)

Minimising Fabrication and Installation Flaws to Ensure Overall Structural Integrity Mitigation Plan, RBI and Maintenance; Kaushik Mukherjee;

Page 47

PETRONAS GHSE Risk Matrix


Page 48

Challenges and Constraints • Establishing the Present Platform condition (missing data: corrosion, marine growth, water level, damage, scour etc) • Continuous application of new technologies (e.g. aging effects, P-Y stiffness, capacity of grouted tubular joints) • Information for adopting Vendor Proprietary Technologies (e.g. Tarpoon structures guyed wires and etc.) • Development of Structural Integrity Management Systems for Data Management, Interpretation and Assessments, Inspection and Maintenance and Reporting Activities • Incorporation of Reliability requirements during FEED or detail design.


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Advancement in Requalification process • Economic capture of inspection information directly into database (Real Time) • More work warranted on the effects of fatigue in the actual collapse of structures for structures in Malaysian waters. • ROVs extend capabilities cleaning members and performing more NDT testing • Older structures have missing or questionable foundation data – there is a need for non-intrusive method for confirming soil and pile properties


Page 50

Advancement in Requalification process (cont..) • Current API recommended design practices for foundation design need to be refined based on actual load test of piles or some practical engineering methods • Requirement for platforms to be equipped for monitoring equipments (e.g. to record seismic motions, dynamic motions, gradual changes of platform subsidence or movements and etc.) • Compilation and dissemination of high quality near-miss and accident data (i.e. for evaluation of root cause and remediation) • Systematic evaluation technique for better control of human and organisational errors • Establishment of Malaysian standards for requalification process


Page 51

General Risk Mitigation Recommended Methodology 1. Identification of Prioritized Systems of Evaluation – business critical elements (BCEs) and safety critical elements (SCEs) 2. Walk-down Assessment – A qualitative assessment focused on the important systems. 3. Analytical Assessment – This includes calculations on as as-needed basis. 4. Mitigation – Risk mitigation can include structural modifications, maintenance, system modifications and changes to the operating procedures. [ALARP]


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Seismic Risk Mitigation Topsides DESIGN  Development Floor Spectra to Design Proper Tie-Down  Design to Remain Functional After the Event

INSPECTION  To Check the Tie-down of SCE and BCE  Plan and Inspect the Topside after Each Event to Check the Support Conditions and Mitigations as Required


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Seismic Risk Mitigation Recommended Good Practices • Identify platforms of particular importance that must continue to operate • Incorporate design considerations into Hazard and Operability studies (HAZOPs) using appropriate structural engineering personnel as necessary • Incorporate structural assessments into management of change procedures for the platform to ensure inadvertent changes do not increase vulnerability • Incorporate storm/earthquake response into emergency preparedness plans.


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Conclusion The application of this detailed assessment is to enable the requalification of ageing platforms that satisfies structural integrity compliance, and results in:  No costly strengthening  No costly underwater inspection  No de-rating of facility  No prevention of further/future upgrading  Extension of Platform life for continuous production/operation


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Thank You

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