A large part of the Norwegian gas and oil production facilities has reached their initial design life, but the respective fields are still producing substantial levels of hydrocarbons. In order to ensure technical and operational integrity of these ageing facilities the Norwegian oil industry Association (OLF) has initiated a project to establish the necessary standards and guidelines for assessing and ensuring safe life extensions. This paper presents this project and the headlines of these standards and guidelines.

1. SPE 2010-127134
Final
Life Extension of Aging Petroleum Production Facilities Offshore
Gerhard Ersdal, Ph.D. Per Otto Selnes, M.Sc.
Principal Engineer Manager Operations
Norwegian Petroleum Safety Authority Norwegian Oil Industry Association
Abstract
A large part of the Norwegian gas and oil production facilities has reached their initial design
life, but the respective fields are still producing substantial levels of hydrocarbons. In order to
ensure technical and operational integrity of these ageing facilities the Norwegian oil industry
Association (OLF) has initiated a project to establish the necessary standards and guidelines
for assessing and ensuring safe life extensions. This paper presents this project and the
headlines of these standards and guidelines.
Introduction
Technical and operational integrity of offshore facilities on the Norwegian Continental Shelf
(NCS) is very important for all stakeholders. It concerns the safety, health and welfare of
offshore employees and their families. The external environment shall not suffer, the owners
want no interruption of their revenues, nor do the government and the citizens of the country.
This last item has special interest to Norway as the recovery of the oil & gas resources
offshore Norway counts for about 25% of Norway’s GNP, 35% of the state income, 20% of
all investments and 50% of the export value. It is therefore a priority for oil and gas producers
offshore Norway, as well as for the Norwegian authorities to continue to use the existing
portfolio of facilities in a safe manner on order to maximise the oil and gas production and
recovery.
In Norway, the operators also need consent to operate. Such consents are given for a certain
period, often dictated by the predicted reservoir and production life. Accordingly, installations
and pipelines are often designed for the initial consent period and maintained with the same
time frame in mind. With application of new technology, the recovery factors have been
steadily increased over many years, e.g. from 20 to 50%. As a result of the extension of
reservoir lifetime, an increasing number of offshore oil & gas installations are planned to be
operated beyond their initially planned life, it being the design life or the time period
coinciding with the consent period granted by the authorities. Hence, the owners and
operators need to ensure themselves, as well as the authorities, that these facilities can be
operated for a substantially prolonged period.
The Norwegian Petroleum Authority (PSA), The Norwegian Oil Industry Association (OLF)
and the companies themselves have initiated a number of activities related to aging and
lifetime extension on the Norwegian shelf. This paper presents the activities carried out by
OLF on behalf of its member companies and in close contact with the PSA. Further
information about this work is also presented on OLF’s web-pages (www.olf.no).
Information can also be found on PSA’s web-pages (www.psa.no), on PSA’s activities in the
same area.
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2. Scope
The OLF work has been carried out in two parts, firstly to develop and issue recommended
guidelines, outlining a proposal for the preparation of the application of a new consent
required prior to use of a facility exceeding the consent period; then to develop tools
necessary to assess continued safe operation. The latter was split in the following areas: Risk
management, Working environment, Structural integrity, Technical safety systems, Drilling &
well systems, Top side process & utility systems, Transport systems (pipelines etc.); and Sub
sea systems.
The actual work in these groups has been performed by representatives from OLF member
companies, under a project management and funding form OLF. In most cases, parts of the
development have been undertaken by consulting companies, mainly Det norske Veritas.
Deliveries
The following documents have been delivered:
• A recommended guideline for assessment and documentation of service life extension
of facilities, including an outline of a proposal for the preparation of the application
for consent for a new period
• A document giving detailed comments and recommendations concerning the areas of
Risk management, Technical safety systems and Working environment.
• A new Norwegian NORSOK Standard, N-006, regarding the Assessment of structural
integrity for existing offshore load-bearing structures
• A list of issues that may be addressed in the area of Drilling & well systems
• A list of systems that should be addressed regarding Top side process and utility
systems
• A new Norwegian NORSOK standard for Transport systems (pipelines etc.)
• A new Norwegian NORSOK standard for Sub sea system
A flavour of the contents of each document is given below. The documents can be viewed at
www.olf.no, with their indexes given in the appendices.
OLF Recommended Guideline for the assessment and documentation of service life
extension of facilities (34 pages – full index in Appendix 1)
This recommended guideline outlines a proposal for the preparation of the application of
renewed consent required prior to use of a facility exceeding the current consent period,
which may coincide with the initial design life. The guideline identifies how the operators can
assess and document safe operation of facilities for an extended period, and they facilitate the
preparation the Application for Consent for Life Extension by proposing a consistent
framework and a level of detail for the information that is required for the application.
The guideline describes the analyses and evaluations that should be undertaken, how the
application process should be organised and how the application document should be
compiled. These guidelines must be used together with the applicable regulations and the
requirements stated therein. Another objective of the guidelines is to make the evaluation and
application process efficient, likewise the handling process carried out by the PSA.
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3. It is recommended to start the evaluation and application process at least two years prior to
the expiry of the current consent period, as it may take a year or more to complete the internal
company processes, and up to a year for PSA to handle the application.
A key chapter of the guideline is the one on “Analyses and evaluations”. The operators’
analyses and evaluations shall demonstrate an understanding of how time and aging processes
will affect HSE, technical integrity and resource exploitation and identify measures required
to mitigate the impact of time and aging processes. The Operator may already have analyses
and evaluations that are carried out on a regular basis or have been carried out for a specific
purpose. Such analyses and evaluations are part of the verification process that ensures
regulatory compliance. These can be included in the application if still relevant. It is
important to note that it is not always necessary to carry out new analyses and evaluations if
existing ones are still valid. A typical specific purpose is lifetime extension projects that are
started as a result of higher potential in the reservoir and a desire to improve the economics in
the mature phase in the field development.
Sub-chapters include recommendations in the following areas: Structural Integrity, Technical
Integrity and Conditions, Gap analysis against the Facilities Regulations, Changes to
Operational Conditions, Maintenance and Inspection, Barriers, Wells, Drilling systems,
Pipelines, Verification of ’as built’ documentation, Risk Assessment, Emergency
Preparedness and Response, Environment, Working Environment, Compliance with the
Regulations, Technology, Organisation, Management of Change, and Exemptions. All gaps
against current regulations shall be evaluated and the ALARP (as low as reasonably
practicable) principle applied in the evaluation. The gaps can be closed through technical,
organizational or administrative changes or a combination of these. The evaluation of the gap
may also indicate that it may not be worthwhile making any changes due to the risk and/or
cost of implementation.
Risk Management, Technical Safety Systems and Working Environment. Safety
Systems And Working Environment (7 pages)
This document gives detailed comments and recommendations for the assessment of facilities
concerning the areas outlined. On risk assessment it recommends Quantitative Risk Analysis
(QRA) and necessary sensitivity studies to be updated addressing the scenario and operating
conditions envisaged during the life extension period. The QRA will act as a decision support
for choice of operation modes, activity levels and for ranking and selection upon risk reducing
measures as identified in the range of studies performed, i.e. the Gap study.
This is a risk update of the installations operational phase vs. a design QRA, therefore, a lot of
installation specific input data is available. Hence, the validity and quality of the QRA
assumptions and input data should be carefully evaluated in light of information about
installation configurations, technical condition status and platform specific data.
Evaluations of factors that may be expected to change over time should be included in the
sensitivity evaluations. Examples of such factors that should be considered are, but not limited
to change in number of wells and/or well configuration (production, injection, gas lift...);
process/process data (from oil to gas, pressure/temperature change…); equipment density; the
likelihood of leaks/changed number of leakage points (typically a change in the number of
flanges); operations (drilling, number/type of well operations…), staffing and operating
hours; number of hours of hot work; helicopter shuttling activity; the number of boat calls; or
change in structural strength. Note: The term Total Risk Analysis (TRA) is also used in the
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4. industry. The terms QRA or TRA are not quoted in the HSE regulations. The regulations refer
to risk analysis. Risk acceptance criteria and any other risk parameters that are introduced /
applied in connection with the life extension evaluation should be presented in the document.
The criteria must be defined and agreed upon prior to the analyses, including the Gap
analysis, and the evaluations of possible risk reducing measures.
Structural Integrity for Existing Offshore Load-Bearing Structures (58 pages – full index
in Appendix 2)
NORSOK N-006 standard gives requirements for assessment of the structural integrity of
offshore structures in-service and for life extension, additional to NORSOK N-001, Integrity
of offshore structures, which is the principle standard for offshore structures, and which refers
to ISO 19900, Petroleum and natural gas industries - General requirements for offshore
structures.N-006 serves as an alternative to NORSOK N-001 for cases where structures are to
be operated beyond original design requirements and structural resistance is not easily
verified through ordinary design calculations, and where use of additional information gained
through the life of the structure can be used to demonstrate structural adequacy.
NORSOK N-006 is applicable to all types of offshore structures used in the petroleum
activities, including bottom founded structures as well as floating structures. As the majority
of ageing facilities are fixed structures of the jacket type, the detailed recommendations given
are most relevant for this type of structure. The standard is applicable to different types of
materials used including steel, concrete, aluminium, etc. For assessments of structures of
other materials than steel the detailed requirements that may be needed should be developed
on a case by case basis, and it is applicable to the assessment of complete structures including
substructures, topside structures, vessel hulls, foundations, marine systems, mooring systems,
sub sea facilities and mechanical outfitting that contributes to maintain the assumed load
conditions of the structure.
N-006 recommends that an existing structure shall be assessed to demonstrate its fitness-for-
purpose if one or more of the following conditions exist: changes from the original design or
previous assessment basis; damage or deterioration of a primary structural component or a
mechanical component which contributes to maintain the assumed load conditions of the
structure; or when exceeding the design service life. The general assessment process is shown
in Appendix 3.
Areas of particular attention are those structural details that are of critical for the total
integrity of the structure and cannot be inspected, e.g. the piles. For the fatigue assessment of
piles, a development in this project has led to new specific design fatigue factors for
calculation of fatigue damage from pile driving. These new design fatigue factors are intended
to be used in combination with actual pile driving records, and without such information the
regular design fatigue factors should be used. The new proposed design fatigue factors are
given in the standard.
For installation structures not meeting to day’s Accidental Limit State criteria for
environmental loads, recommendations have been made on how to determine forecasted sea
state required in order to decide de-manning before storms hit the installations.
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5. Drilling & Well Systems (One page)
For Drilling and well systems a checklist has been established, with elements that should be
considered during the assessments of continued safe drilling and well operations.
General considerations and requirements:
• Brief status on drilling facilities & wells, with description of current service life,
technical condition, main capabilities, and conformity to current regulations/
exemptions. relevant incidents and Well Integrity KPI records expected to be followed
up
• Main degradation mechanisms and corresponding control measures relating to “Safety
Critical Equipment”
• Well integrity situation and potential changes in the related risk-picture (locally and
towards other parts of the installation)
• Potential well stimulation, intervention & work over methods/ limits
• Future activity level and modification plans
• Future capabilities required to monitor, access, operate, maintain and abandon drilling-
and well facilities during the extended lifetime
• Condition of utility systems to support future D&W activities
• Future capabilities to serve for potential “tie-ins” and specific measures for enhanced
petroleum recovery in the area
Some other potential issues to be considered:
• Verification/analysis of load-bearing structures for such as derrick w/sub-structure,
handling arrangements and well head strength.
• Condition of support arrangements for well/ wellhead/ conductors, (impact by wear,
motion, subsidence)
• Plans for testing integrity of wells/ well barriers, for extended use
• Systematic checking for leakages and monitoring annulus pressures
• Impact/ degradation inside and outside of the well/ barrier envelopes (by H2S, CO2,
other chemical, erosion, corrosion, deformation, fatigue, wear,…)
• Well control facilities and well killing capabilities
• Technical premises for potentially converting wells (e.g.: from production to
injection,..), slot recovery demands and new wells/ well paths
• Potential impact on interfacing facilities/outfitting (e.g.: flow lines)
• Strategy relating to P&A
• Well integrity competence/ resources
Recommendations:
• Start developing the extension application early, and include Drilling & Well
personnel from day 1. Agree on the scope, and consult with PSA professionals if
uncertainties exist
• Emphasize proper verifications, realistic plans and committed execution
• Know how to adhere to Norsok D-010, and ensure Well Integrity assessments/ records
is up-to date.
• Ensure drilling and well systems are sufficiently managed/ evaluated in this context
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6. Top Side Process and Utility Systems
A list of systems that should be addressed during assessing life extension of top side’s process
and utility systems has been established. The scope of this part includes process systems from
wellhead wing valve to riser ESDV, Auxiliary and support systems and Process Control
System / Process Shutdown System.
A general checklist has been developed, containing “common factors” to be considered when
evaluating the integrity of process and utility systems. The checklist has been designed to
provide prompts/checklist items that are specific to aid in assessment of the individual
systems, focusing on ageing of the systems. This would specifically include;
• Have conditions changed from when the system was designed?
• Will future operations still be within the capabilities of the system?
• Could specific studies be required (list typical studies for individual systems)
As an example, relevant checklist “prompts” for the flare system could be (list not
exhaustive);
• Adequacy of relief capacity
• PSV sizing (over/under sized)
• Fatigue assessments
• Status of flare system model (are all relief sources modelled)
• Validity of original analysis compared with current knowledge / “modern” calculation
methods
Transport Systems (Pipelines Etc.) (41 pages – full index in Appendix 5)
The transport system in this context is facilitating transport through pipelines, risers and
loading hoses intra-field, inter-field and as trunk pipelines to shore and onshore. There is also
a wide range of materials that are used for pipe, with new materials being continuously
qualified. The main groups of pipes are identified as: metallic pipes, un-bonded flexible pipes,
and bonded flexible pipes. A transport system is exposed to external as well as internal
threats. The potential internal threats to a pipeline may be dependent of the transported
medium. Typical threats are corrosion, erosion, wear, chemical and physical ageing, creep,
overpressure, under-pressure and changes in flow characteristics. The potential external
threats to a pipeline will be the same independent of the transported medium. The various
threats will vary along the pipeline. Typical threats are external corrosion, free spans
(fatigue), free spans (trawl pullover and hooking), lateral buckling, upheaval buckling,
expansion, on-bottom stability, collapse, compression, design, fabrication and installation
“shortcomings”, installation damage (dents, abrasions, etc.), natural hazards, other third party
damages (sinking ships, dropped objects etc.), incorrect operation, deteriorating integrity of
supporting components/ structures (buoyancy elements, mid-water arch, pipe support etc.),
and deteriorating integrity of surrounding infrastructure (tunnels, bridges, etc).
Sub Sea Systems (120 pages – full index in Appendix 6)
Subsea systems are increasingly used on the Norwegian Continental Shelf and this standard is
prepared as to support the process of assuring technical integrity of the sub sea system and its
elements beyond the original approved service life. Further, operational integrity and
regularity will be covered where this is essential for the function e.g. for the control system.
Subsea systems consist of many and complex sub-systems and components. Each part has a
range of characteristic properties which need to be assessed when quantifying the expected
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7. lifetime. There are a large number of applied standards and codes in the industry that also
need to be considered. .
Battery limits for the Subsea system are general at contact point with the following systems:
Transportation systems – Pipelines
Topside systems - Hydraulic, power, DCS, chemical supply
Well – XT Connector, see also Appendix 6
A sub sea system is exposed to external as well as internal threats. The threats also have
different characteristics these include: Event based e.g. dropped objects, dragged/dropped
anchor, drill pipe etc. Condition based; e.g. change in operational parameters and Time
based; e.g. excavation/ scouring, ineffective corrosion protection or corrosion control.
The combined effect of threats shall also be considered. New threats based on new or
changed design premises including new regulations, shall be identified.
The document sets out a standardised assessment and qualification process and follows those
steps through for each of the dominant Subsea equipment types. Specific advice is given on
typical failure modes and recommendations are made on mitigations that can be taken to keep
risks to within acceptable limits.
CONCLUSION
The guidelines, standards and checklists developed through this project will provide valuable
assistance to offshore facility owners and authorities when assessing the condition of aging
facilities, and if they can be safely operated for a new consent period.
Acknowledgements
The authors want to thank all work group representatives from OLF member companies BP,
ConocoPhillips, E.ON Ruhrgas, ExxonMobil, Gassco, Hess, Shell, Statoil, Talisman; from the
unions IndustryEnergy, SAFE and Lederne; and the consulting firms David Llewelyn, Det
norske Veritas, Graeme Dick, Jan Krokeide, Ocean Design, Proactima and Pöyry for their
contributions on the development of the documents described in this paper.
Funding, management, working method and organisation
The OLF work was funded and managed by OLF, and has been carried out over a period of
3.5 years. The cost has been some NOK 6 millions in external contract cost, plus an estimate
expense of some 2 mill NOK for project management and the contribution by company and
external representatives in the various work groups. Work groups were formed for each area,
but work related to Risk management, Technical safety systems & Working environment was
supervised by the same work group. The groups were chaired by, and consisted of,
representatives from OLF oil & gas companies and for all but one, consultants were hired in
as work group assistants, taking notes and drafting work group recommendations. The work
group on Risk management, Technical safety systems & Working environment also included
union representatives. In addition a reference group consisting of high ranking company
representatives and authority and union representatives acted as sounding board for project
strategy and draft documents. The main task of the work groups was to determine the scope of
the work to be done. During that work, the PSA was consulted at least once by each work
group. Such consultation took place as a work meeting at the PSA office. When the scope had
been defined, an engineering and consulting company was hired in to develop a document
described in the scope. This has resulted in three new Norwegian NORSOK standards and one
checklist. In two cases a checklist was develop by the work group, one assisted by the
contracted consultant.
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8. Nomenclature
ALARP - as low as reasonably practicable
CO2 – Carbon dioxide
CT – Coiled tubing
DSC –Distributed control system
D&W – Drilling and well
ESDV- Emergency shut down valve
GNP – Gross national product
HIPPS – High integrity protection systems
H2S – Hydrogen sulfide
HSE - Health, safety and environment
KPI – Key performance indicator
NCS - Norwegian Continental Shelf
NPD - Norwegian petroleum Directorate
NOK – Norwegian kroner
NORSOK – Standards developed by the Norwegian petroleum industry
OLF - Norwegian Oil Industry Association
P&A – Plug and abandon
PLEM - Pipeline end module
P/L - Pipeline
PSA – The Norwegian Petroleum Safety Authority
PSV – Process safety valve
QRA - Quantitative risk analysis
TRA – Total risk analysis
W/L – Wire line
XT – Xmas tree
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9. APPENDICES
1. OLF Guideline 122: Recommended guidelines for the assessment and documentation
of service life extension of facilities
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10. 2. NORSOK Standard N-006: Assessment of structural integrity for existing offshore
load-bearing structures - Index
10

11. 3. Flow sheet of the assessment process
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12. 5. Transportation Systems - Index
Foreword.........................................................................Feil! Bokmerke er ikke definert.
Introduction....................................................................Feil! Bokmerke er ikke definert.
1 Scope...............................................................Feil! Bokmerke er ikke definert.
2 References......................................................Feil! Bokmerke er ikke definert.
3 Terms, Definitions, Abbreviations and Symbols ..... Feil! Bokmerke er ikke
definert.
3.1 Definitions ...................................................Feil! Bokmerke er ikke definert.
3.2 Abbreviations ..............................................Feil! Bokmerke er ikke definert.
4 Assessment Methodology ...........................Feil! Bokmerke er ikke definert.
4.1 Objective......................................................Feil! Bokmerke er ikke definert.
4.2 Integrity Management System ..................Feil! Bokmerke er ikke definert.
4.3 Life Extension Process..............................Feil! Bokmerke er ikke definert.
4.4 Degradation .................................................Feil! Bokmerke er ikke definert.
5 Life extension Premises...............................Feil! Bokmerke er ikke definert.
5.1 Objective......................................................Feil! Bokmerke er ikke definert.
5.2 Authority regulations .................................Feil! Bokmerke er ikke definert.
5.3 Design Standards........................................Feil! Bokmerke er ikke definert.
5.4 Design Premise ...........................................Feil! Bokmerke er ikke definert.
5.5 Threats to the transportation system ......Feil! Bokmerke er ikke definert.
5.6 System Overview ........................................Feil! Bokmerke er ikke definert.
6 Integrity Assessment ....................................Feil! Bokmerke er ikke definert.
6.1 Integrity Management System ..................Feil! Bokmerke er ikke definert.
6.2 Data Collection ...........................................Feil! Bokmerke er ikke definert.
6.3 Condition Assessment ...............................Feil! Bokmerke er ikke definert.
6.4 Remedial actions.........................................Feil! Bokmerke er ikke definert.
7 Reassessment.................................................Feil! Bokmerke er ikke definert.
7.1 Objective......................................................Feil! Bokmerke er ikke definert.
7.2 Process overview ........................................Feil! Bokmerke er ikke definert.
7.3 Acceptance level .........................................Feil! Bokmerke er ikke definert.
7.4 Design Based Reassessment .....................Feil! Bokmerke er ikke definert.
7.5 Condition Based Reassessment................Feil! Bokmerke er ikke definert.
8 Modifications.................................................Feil! Bokmerke er ikke definert.
8.1 Mitigation.....................................................Feil! Bokmerke er ikke definert.
8.2 Intervention.................................................Feil! Bokmerke er ikke definert.
8.3 Repair............................................................Feil! Bokmerke er ikke definert.
8.4 Replacement ................................................Feil! Bokmerke er ikke definert.
9 Document ......................................................Feil! Bokmerke er ikke definert.
10 Implement......................................................Feil! Bokmerke er ikke definert.
Annex A (Informative) Illustration of re-qualification schemes for life extension Feil!
Bokmerke er ikke definert.
Annex B (Informative) Work Process Paradigm Feil! Bokmerke er ikke definert.
Annex C (Informative) Condition Based Assessment Feil! Bokmerke er ikke definert.
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13. 6. Sub Sea Systems - Index
Foreword
Introduction
1 Scope
2 References
3 Terms, Definitions, Abbreviations and Symbols
3.1 Definitions
3.2 Abbreviations
4 Assessment Methodology
4.1 Objective
4.2 Integrity Management System
4.3 Life Extension Process
4.4 Degradation
5 Life extension Premises
5.1 Objective
5.2 Authority regulations
5.3 Design Standards
5.4 Design Premise
5.5 Threats to the subsea system
5.6 System Overview
6 Integrity Assessment
6.1 Integrity Management System
6.2 Data Collection
6.3 Condition Assessment
6.4 Remedial actions
7 Reassessment
7.1 Objective
7.2 Process overview
7.3 Acceptance level
7.4 Design Based Reassessment
7.5 Condition Based Reassessment
8 Modifications
8.1 Mitigation
8.2 Intervention
8.3 Repair
8.4 Replacement
9 Document
10 Implement
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14. Annex A Subsea System Specific Requirements for Life Extension
Annex B XT Specific Requirements for Life Extension
Annex C Manifold & Structures Sp Specific Requirements for Life Extension
Annex D Valve Specific Requirements for Life Extension
Annex E Manifold Piping & Interconnecting Piping Specific Requirements for Life Extension
Annex F Umbilicals Specific Requirements for Life Extension
Annex G Power & Control Specific Requirements for Life Extension
Annex H Tether & Buoancy Specific Requirements for Life Extension
Annex I (Informative) Illustration of re-qualification schemes for Life Extension
Annex J (Informative) Work Progress Paradigm
Annex K (Informative) Condition Based Assessment
7. Sub Sea Interfaces
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