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This document was prepared by the members of Oil & Gas UKs Decommissioning Efficient
Execution Workgroup. Particular recognition is given to the input of Ian Fozdar who led the activity.
Issue 1 - 2015 Edition
ISBN: 1 903 004 57 8
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Guidelines on Late-Life/DecommissioningInspection and Maintenance
Contents
Foreword
Paragraph Page
1.
Introduction 1
2.Offshore Decommissioning Workflow 2
2.1 Definitions of the Decommissioning Phases 2
3.Late-Life/Decommissioning Cost Reductions 5
4.
Inspection and Maintenance Assessment Process 8
4.1 Inspection and Maintenance Framework 8
5.Implementing the Framework 11
Appendix 1 13Abbreviations 13
Appendix 2 14
Worked Example Operations, Inspection & Maintenance Framework 14
Table
Table 1 Hazard and Safety Critical Elements Matrix 8
Table 2 Operations Inspection & Maintenance Framework 10
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Guidelines on Late-Life/DecommissioningInspection and Maintenance
1. Introduction
Maintenance during the late-life and decommissioning phases of infrastructure
is driven by very different objectives and constraints than during the steady-
state Operating phase.
Robust Health, Safety and Environment (HSE) management is now typically
in the context of reduced hydrocarbon inventories and pressures.
Production-critical maintenance typically becomes more reactive, and then
ceases.
Equipment and human-access related maintenance becomes solely driven
by the needs of decommissioning/dismantlement, which were virtually non-
issues during the Operating phase.
Inspection may be designed more to understand the condition of a platform,
so that decommissioning plans can be fitted to this, and less to confirm thatsome pre-determined performance standard is being met.
Overall Inspection/Maintenance man-hours and costs can be reduced, often
significantly, during decommissioning. The challenge is to avoid the threats to
safety and integrity throughout the project. The experience of Oil and Gas UK
members has produced two matrices to provide:
An enabler for managing the changing HSE hazards during late-
lif /d i i i
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Guidelines on Late-Life/DecommissioningInspection and Maintenance
2. Offshore Decommissioning Workflow
As the workflow moves through each Decommissioning Phase the inspection
Need to managefor productionphase & futuredecom phase
needs
Need to manageSafety CriticalElements &
current/futuredecom phase
needs
Need to manage reducing no. of Safety Critical Elements, and inspect/maintain
for current/future decom phase needs
End of production-related
insp./maintenance
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o Environmental Management System: All environmentally criticalelements defined the Environmental Management System for thelevel of suspension are to be inspected/maintained.
Warm Suspension, Live Wells (only applicable for structures with
wells)
o The platform/subsea structure has permanently ceased production.o Wells: All wells have not been permanently Plugged and
Abandoned.o Pipelines: Import & export pipelines have been decommissioned.o Secure from health, safety and environmental hazards to agreed
standards.o Topsides: Process pipework has been decommissioned from the
riser to the production tree of each well, and to any connectedplatforms.
All process equipment (compressors, pumps, control systems,etc) decommissioned ready for removal
Secure from health, safety and environmental hazards toagreed standards.
o Safety Management System: All Safety critical elements defined inthe Safety Management System for this level of suspension are tobe inspected/maintained.
o Environmental Management System: All environmentally criticalelements defined in the Environmental Management system for thislevel of suspension are to be inspected/maintained.
Warm S spension (Li e Process)
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Secure from health, safety and environmental hazards toagreed standards.
o Manning:
Manned: The platform is manned, with accommodation,personnel welfare systems and utilities inspected andmaintained to agreed standards.
Unmanned: The platform is normally unmanned, with requiredemergency refuge, personnel welfare systems and utilities
maintained to agreed standards.o Safety Management System: All Safety critical elements defined in
the Safety Management System for this level of suspension are tobe inspected/maintained.
o Environmental Management System: All environmentally criticalelements defined in the Environmental Management system for thislevel of suspension are to be inspected/maintained.
Partial Removal, manned or unmanned
o The platform/subsea structure has permanently ceased production.o Wells: All wells have been permanently Plugged & Abandoned and
conductors cut below seabed at agreed depth.o Pipelines: Import & export pipelines have been decommissioned.o Secure from health, safety and environmental hazards to agreed
standards.o Topsides: Process pipework has been decommissioned from the
riser to the production tree of each well, and to any connected
l tf
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Guidelines on Late-Life/DecommissioningInspection and Maintenance
3. Late-Life/Decommissioning Cost Reductions
The sources of cost reduction are typically driven through reductions in
inspection, maintenance and consumables needs. Some examples of direct
and indirect cost savings may include:
Experience from infrastructure in the other regions indicates that inspection &
maintenance during decommissioning can be safety and steadily downscaled
through effective management of activities.
Th h t Fi 1 b l ill t t t d f t i lth h t
Direct Savings Offshore manhours
Onshore manhoursSpare parts and Inventory
Indirect Savings Documentation reduced
Helicopter flights / Supply boats
Accommodation costs
Manager and Technical Authority time
Other Benefits HSE improvements as fewer man-hours offshoreFocussed maintenance leads to better reliability
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Decommissioning Phase: Potential high intensity activity:
Warm Suspension / Warm Stack Freeing of hydrocarbons and wellplugging & abandonment
Engineering and installation of lift points
Removal Removal, including use of barges andheavy lift vessels
Dismantle and Dispose Dismantling and disposal
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a) Large, Manned Installations
Limited scope for pre-cessation cost reductions due to high fixed OPEX & startof decommissioning
b) N ll U d I t ll ti (NUI
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4. Inspection and Maintenance Assessment Process
This section describes a process by which inspection and maintenance
requirements during the late-life and decommissioning phases can be
assessed.
4.1 Inspection and Maintenance Framework
A key difference between Decommissioning and Production Operations is thetype of hazards encountered. During production, the hazards remain constant
(such as loss of containment) whereas the hazards encountered duringdecommissioning change substantially from Cessation of Production (CoP) tocompletion of the decommissioning project, typically reducing as the
decommissioning phases are progressed.
Certain hazards will disappear as decommissioning progresses (e.g. with
removal of process hydrocarbons, there is no risk of Loss of Containment). It
may also be that the risk of Fire and Explosion is not present, depending onwhether factors such as presence of utility hydrocarbons such as diesel.
One of the keys to reducing inspection and maintenance is the efficientmanagement of changing safety requirements.
A useful tool to ensure that all hazards are recognised and properly managedis to build a Hazard and Safety Critical Elements Matrix.
T bl 1 b l t l H d d S f t C iti l El t M t i
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When all hazards associated with a given SCE have been eliminated, bydefinition that SCE becomes redundant, and inspection/maintenance for it may
be discontinued.
This justified reduction in inspection/maintenance can then be mapped on to a
Operations, Inspection & Maintenance Matrix, as illustrated in Table 2. Thisallows the changes in Inspection & Maintenance requirements to be mapped-out in advance.
The horizontal axis indicates the decommissioning phase that a platform is in,and the vertical axis the various equipment and systems for which maintenance
is being managed.
Based on the HSE logic illustrated in the Hazard & SCE Matrix shown before,
justified reductions in HSE-related inspection/maintenance can be agreed and
summarised in this table.
The format is generic, and the titles on the 2 axes (horizontal & vertical) can be
modified as required to fit internal workflows and maintenanceframework/definitions.
In some cases (life boats, walkway gratings etc.) no reduction in inspection &maintenance can be achieved regardless of whether a platform is operating or
in the decommissioning phase (e.g. a manned platform will have evacuationneeds even when hydrocarbons are removed). This unchangedinspection/maintenance regime is referenced by a green-coloured cell.
Wh ti l d ti i i ti & i t f ibl b
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10 October 2015
Operations & Maintenance framework Bases for Inspection & MaintenanceStrategy
Health (Present, Future)
Legend Safety (Present, Future)
Fully Maintained Environment (Present, Future)Partially Maintained Reliability (Present, Future)
No maintenance Production Phase Warm Suspension (Fully Live) Warm Suspension (LiveWells)
Warm Suspension (LiveProcess)
ColdSuspension
PartialRemoval
Performance Standards (Present,Future)
Pre-late life Late life Insp. &Maintenance
Final Clean &Disconnect
Plug &Abandon
Insp. &Maintenance
Plug &Abandon
Insp. &Maintenance
Final Clean &Disconnect
EQUIPMENT /ITEM
SCE COMMENTS
HSE
HSE
HSE
HSE
HSE
HSE
HSE
HSE
HSE
HSE
Production
Production
Production
Production
Production
Utilities
Utilities
Access
Access
Table 2 Operations, Inspection & Maintenance Framework
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5. Implementing the Framework
An example of how one Operator applied the Operations, Inspection &
Maintenance framework is as follows:
(a) Ensure Governance document exists that drives Business Plan process
to determine premised CoP dates (& uncertainty)
(b) Identify different phases & milestones of late-life & decommissioning
(c) Outline the requirements for the different phases of decommissioning
Modify existing maintenance philosophy & strategy documents
Main focus will be on safety critical maintenance
(d) Several years before CoP, carry-out review of planned & corrective
maintenance routines & budget drivers to identify maintenance work that
can be eliminated during the late-life & decom phases
Carry out risk-assessments / Management of Change (MoCs) as
appropriate.
Ensure discipline Technical Authorities (TAs) are involved
Regulatory & industry standards to be maintained where required.
incl. Safety Case & Verification and Examination Scheme (VES)
programme
( ) Adj t i t t t t fl t h ( SAP
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Appendix 2 presents a worked example of the Operations, Inspection &Maintenance Framework.
The example shows a limited number of line items for visibility, although inpractise there could be a much larger number of systems on platforms which
offer potential for changed inspection/maintenance.
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Appendix 1
Abbreviations
CoP Cessation of Production
ERRV Emergency Response and Recovery Vessel
HSE Health, Safety and Environment
ICP Independent Competent Person
IVB Independent Verification Body
MoC Management of Change
NavAids Navigational AidsNUI Normally Unmanned Installation
P&A Plugging and Abandonment
SCE Safety Critical Element
TA Technical Authority
UKCS United Kingdom Continental Shelf
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14 October 2015
Appendix 2
Worked Example Operations, Inspection & Maintenance FrameworkOperations & Maintenanceframework
Bases for Inspection & MaintenanceStrategy
Health (Present, Future)
Legend Safety (Present, Future)Fully Maintained Environment (Present, Future)
Partially Maintained Reliability (Present, Future)
No maintenance Production Phase Warm Suspension (Fully Live) Warm Suspension (LiveWells)
Warm Suspension (LiveProcess)
ColdSuspension
PartialRemoval
Performance Standards (Present,Future)
Pre-latelife
Late life Insp. &Maintenance
Final Clean &Disconnect
Plug &Abandon
Insp. &Maintenance
Plug &Abandon
Insp. &Maintenance
Final Clean &Disconnect
EQUIPMENT /ITEM
SCE COMMENTS
HSEAccumulators &Pulsation Dampers
Reactivemaintenance
HSE
Batteries &UninterruptiblePower Supplies(UPS)
For fire & gas systems &communications
HSE Navigation AidsUtilise rig
navigationalaids
Utilise AWVnavigational
aids
MarkerBuoys
Markerbuoys orRemovalvessel
NavAids
Until buoys are installed, or NUI is inCold Suspension
HSE Distribution Boards Safety Critical equipment only
HSE Earthing/Bonding
HSEDiesel System(Tanks andPipework)
HSE Engines: Diesel
HSEFire & GasInstrumentation
HSEAlternators andGenerators
HSE Lighting
HSEMotor ControlCentres (MCCs)
Safety Critical equipment only
HSE Electric Motors Safety Critical equipment onlySafety Critical equipment
only
HSESafe MarineSystem
HSE Small PowerCircuits
Safety Critical equipment only
HSEElectricalSwitchboard
Safety Critical equipment only
HSEPortable Electrical
Equipment
HSE Telecoms
HSE Temporary RefugeReduced
inspection/maintenancerequirement if de-pressurised