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Valhall Corrosion Events and ManagementLearning Pack

Eldar�Larsen,��Head�of�Operations,�BP�Norway.

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Valhall�Corrosion Events - Summary

Summary

• Hydrocarbon�leak�HIPO�on�6th�March�2009�caused�by�Microbial�Induced�Corrosion�(MIC)

− resulted�in�crude�and�gas�leak,�First�Aid�Incident,�emergency�plant�shutdown�&�muster.�

• Valhall�eventually�shutdown�for�10�weeks�for�corrosion�inspection�and�repairs.

− during�which�three�further�incidences�of�MIC�and�44�anomalies�identified.

Major Lessons

• Behaviours of MIC were misunderstood

− Areas�of�high�flow�rate�were�previously�thought�unlikely�to�experience�MIC,�this�assumption�failed�to�identify�internal�pipe�work�scaling�can�provide�environment�for�MIC�activity.

• Inadequate application of hazard Recognition, risk awareness and control of work.�

− The�initial�inspection�routine�was�inappropriate�and�directly�led�to�exposure�of�the�individual�and�the�resultant�FAI.�

• 15�specific�improvement�opportunities�identified�as�a�result�of�the�incident�and�plant�investigations�(7�organisational,�5�work�process�and�3�performance�management).

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Microbial Induced Corrosion

What�is�MIC?

• MIC�is�Microbial�Induced�Corrosion.

• MIC�of�carbon�steel�typically�manifests�itself�as�localised�corrosion�or�pitting�attack�following�the�development�of�a�surface�biofilm.

• The�anaerobic�environments�of�oil�and�water�transport�pipework�often�support�the�growth�of�biofilms,�which�almost�invariably�contain�sulphate-reducing�bacteria�(SRB),�a�major�cause�of�MIC.�

• SRB�containing�biofilms generate�H2S.

• H2S�results�in�formation�of�Iron�sulphide�within�the�biofilm.�

• Iron�sulphides�are�cathodic�to�bare�steel�and�can�have�the�effect�of�greatly�increasing�corrosion�at�anodic�sites.

Why�does�MIC�occur?

• MIC�can�occur�in�all�systems�that�contain�water�with�SRB’s.

• Prediction�of�corrosion�rates�attributed�to�MIC�is�unreliable�

− uncertainty�of�the�onset�of�localized�corrosion/pitting�,whether it�proceeds�at�a�constant�rate.

• Parameters�that�can�influence�MIC�include�pH,�temperature,�nutrition,�velocity�of�fluids,��presence�of�deposits.

• MIC�is�more�likely�to�occur�at�locations�with�low�fluid�velocity such�as�in�dead�legs,�under�deposits,�scale.

• All�metals�are�susceptible�to�MIC.�Carbon�steels�have�generally�been�found�to�be�most�susceptible.

• MIC�mitigation�relies�on�effective�biocide�dosing�regimes.

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Reference - Valhall Timeline

1982

Valhall�start�

production,

Incl.�Jet�

washing

separators�

using sea-

water.�By�

mid-’90’s�

using mainly

produced

water

1998

New�Metering�

Skid�installed.�

Small�bore�

pipe�work�not�

commissioned�

in�Workmate

1999RBI�Analysis�performed�–MIC�internal�corrosion�not�sufficiently�

identified�as�a�threat.

2000

Inspection�

scheme�

constructed�

which�

identified�

external�

inspection�of�

Liquids�

metering�

package�as�a�

whole

2004-2006

Chemical�

cleaning�of�

fast�loop�to�

aid�

calibration�

due�to�scale�

build�up

Ongoing

Biocide�

treatment�of�

Sulphate

Reducing�

Bacteria�

(SRB)�on�

Produced�

Water�(PW)�

system�

ongoing�and�

working

2007

SRB’s in�2nd�

stage�separator�

0-460/ml

Sept 2007

Cor.�Mngt.�Health�

Check:�Valhall�

Prod.�Water�

Sulfate�Reducing�

Bacteria�(SRB)�

contamination�as�

a�high�risk�and�

recommends�a�

microbial�audit�by�

microbial�

specialist

06.Mar.2009

Leak�in�1”

pipe�fast�

loop

HIPO

02.Apr.2009

Upstream�

skimmed�oil�

tank

17.Apr.2009

Leak�in�6”

prod.�water�

pipe

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Reference - Valhall Timeline

Events and response:

6th�March�2009�”Metering�fast�loop” (F&G�→ ESD).

• Limited�awareness�of�MIC,�deemed�low�probability.�Limited�spot�checking�by�X-ray�outside�the�

fast�loop.�No�SD�justified�by�residual�corrosion�risk.�No�additional�resources.

2nd�April�2009�“T-337�pressure�increase” (No�ESD).

• Start�up�after�a�compressor�incident�increased�flare�backpressure�which�burst�a�MIC�in�the�

produced�water�system.�

• 15�days�(6�+�9)�shutdown�looking�for�MIC�with�Eddy�current�and�X-ray�w.�crew�of�3.

17th�April�2009�“6” produced�water�pipe” (No�ESD).

• Restart�attempt�failed�when�a�MIC�burst�in�the�prod.�water�system.�Had�been�inspected�in�very�

close�vicinity.�Increasing�realization�of�the�criticality�of�adequate�inspection�rigour.

• 10�days�shutdown,�100%�inspection�of�prod.�water�system�by�Eddy current�and�X-ray,�extended�

risk�based�approach.�Increased�offshore�resources.

27th�April�2009�“Condensate�return�to�prod.�water�system”.�(F&G�→ ESD).

• Pipe�burst�during�start�up�attempt.�Contained�highly�volatile�condensate.�

• Realized�technology�gap.�Changed�to�SLOFEC�scanning�successfully.�

• 30+�team�offshore.�Task�force�onshore.�True�100%�inspection�beyond�produced�water.�RIB�

revision.

1st�June�2009�“Successful�restart”.

• 10�weeks�of�production�loss�and�serious�HSE�incidents.

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Valhall Corrosion Event (March 6th 2009)

Summary of first event.

• A�‘seep’ or�sweating�leak�observed�coming�from�an�insulated�1” carbon�steel�pipe�was�prepared�for�inspection�following�removal�of�the�insulation.

• The�pipe�was�on�the�crude�export�metering�skid�and�contained�a�mixture�of�crude�oil�and�gas�at�25�bar�pressure.

• On�removal�of�insulation,�the�leak�was�observed�not�to�originate�from�the�flange�as�originally�expected.

• An�inspector�examining�the�pipe�initially�used�a�blade�to�scrape�off�paint�at�the�leak�site.

• During�a�later�visit,�the�inspector�touched�the�leak�site�with�his�finger�and�was�sprayed�in�the�face�with�oil�under�pressure.�

• During�hydrocarbon�release,�the�hole�enlarged�to�10mm�diameter.

• Valhall�went�to�full�Emergency�Shutdown�and�muster.�

Hydrocarbon leak on metering skid – First Aid Incident – Emergency Plant Shutdown

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Inherent Design

Plant Layout

Control, Alarm &

Shutdown system

•Inspection (RBI) and Corrosion Management

practices failed to identify and mitigate the internal corrosion threat/risk that led to the failure•RBI assessment not updated to reflect changes to operating

and/or process conditions

Maintenance

& Inspection

Learning from

the Past

•Actions from 2007/2008 Health Checks to improve Biocide treatment

and to conduct Microbial survey not completed

•Force Inspection procedures inconsistent with requirements of HSE

Directive for visual inspection

Operations

Procedures

•Inspection Engineer

delegated inspection task to NDT Technician.

Effective

Supervision /

Leadership

Training &

Competency

�Failure to follow CoW

and RBI procedures

Work Control

•Inadequate Hazard Recognition and Risk Awareness – job treated as ‘routine’ and Level 2 work permit.

•CoW - Failure to isolate energy source prior to work•CoW - Failure to comply with requirements for ‘Visual Inspection’

Support to Next

of Kin & Injured

Relief and

Blowdown

system

Audit & Self

Regulation

•No apparent MoC for chemical treatment of Fast Loop line.•1” line not identified on risk-based inspection schedule

Management

of Change

Active & Passive

Fire Protection

Escape /

Access

Rescue &

Recovery

HAZARD

Hydrocarbon

Inventory at

25bar in Fast

Loop line

Investigation &

Lessons Learned

HAZARD

REALISATION

Loss of containment

First Aid injury & HiPo

Hazard Barrier Diagram

Heirarchy of control – Bias towards hardware/inherent safety & reducing the scope for human error – multi barrier defence

•Four Point Check

not used.

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Valhall Corrosion Event (April 2nd 2009)Summary of second event.

• A�leak�in�the�Produced�Water�System�followed�

a�gas�compression�upset.�Area�isolated�&�

upstream�vessel�drained.

• 25mm�hole�found�in�drain�line.

• Areas�of�low�flow�and�dead-legs�were�identified�

and�inspected.�6�further�MIC�incidents�

observed.�

• Investigation�initiated�to�ensure�appropriate�

analysis�and�response�prior�to�restart.

• Management�verification�of�process�mitigations�

and�corrosion�mapping�&�repair�effort.

Targeted inspected discovers further incidence of MIC

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Valhall MIC Response The third event: Defining the Scope of Work

• Produced�Water�identified�as�being�the�main�

host�of�Sulphate Reducing�Bacterias (SRB’s)

• Considered�potential�contamination�of�other�

systems�vs�HC�leak�risks.

• Scope�agreed�by�Ops,�Process�TA,�Corrosion�

Mgmt�TA,�Inspection�&�CM�Contractor.

• Produced�Water�System�was�100%�inspected.

• Risk�Based�”Hotspot” Execution�– Water�wetted�

surfaces�eg Low�spots,�Sumps,�Deadlegs etc.

− Waste�injection�on�drilling�platform�(DP).

− Well�systems,�confined�to�slurry�lines.

− Crude�Oil�processing�including�the�

metering�system.

− Closed�Drains�System.

Oil Return from PW Flash Drum to Oil Return tank

Orientation of defect; 9 o’clock position on vertical

pipe

Unpredicted nature and location of corrosion required a new approach to

immediate reaction inspection.

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• Leak�in�6”produced�water�high�flow�pipework

• A�8�mm�hole�was�discovered�during�preparation�for�plant�restart�following�inspection�program�triggered�two�gas�detectors�&�ESD.

• Critical Factor�1�

− Microbial�induced�Corrosion�(MiC)�mechanism�in�the�produced�water�system

• Critical�Factor�2

− Inspection�(RBI)�and�Corrosion�Management�practices�failed�to�identify�the�corrosion�risk�in�high�level,�high�flow�pipework

Targeted inspected discovers further incidence of MIC – in high flow pipework

Valhall�Corrosion�Event.Summary�of�forth�event.

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Valhall MIC project – Inspection

• Extensive�inspection�effort�required�to�execute�

identified�scope�– 30+strong�team.

• SLOFEC�technology�used�

• Priority�1�scope�Identified�44�anomalies

− 23�MIC�Related

− 21�Non-MIC-related

• 19�spools�replaced,�5�temporarily�repaired�&�20�

scheduled�for�ongoing�inspection�following�start-up

• Assurance�processes�followed�by�No�go/Go�

verification�reviews

• Priority�2�inspection�scope�identified�for�post�start�up�

inspection.

No.�10�– T-337�Flange�corrosion

Following fresh focussed risk assessment an intense and prioritised

inspection programme was initiated.

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Lessons Learnt

Direct cause

• Cross�contamination�of�oil�production�system�with�SRB�via�the�produced�water�

system.

• Inadequate�awareness,�inspection�and�mitigation�as�analysis�did�not�identify�oil�

system�as�at�risk�from�SRB�corrosion.

• Insufficient�chemical�injection�(such�as�biocide�and�corrosion�inhibitor)�and�

sampling�and�analysis�to�control�microbial�activity.

• As�a�result�MIC�occurred�within�oil�systems.

Underlying causes

• Improvement�opportunities�identified�within:

− Organization (7�subcategories�with�recommendations)

− Work Processes (5�subcategories�with�recommendations)

− Performance Management (3�subcategories�with�recommendations)