Fjerning av offshore-konstruksjoner - Hva kan vi lære (JIP)? Anette Pedersen, Ingar Scherf, Gudfinnur Sigurdsson

Fjerning av offshore-konstruksjoner - Hva kan vi lære (JIP)? Anette Pedersen, Ingar Scherf, Gudfinnur Sigurdsson

Background Several structures will be decommissioned in the coming years and other structures will extend their life beyond intended design life PSA activity 50: Når innretninger disponeres skal operatøren gjennomføre undersøkelser av konstruksjonenes tilstand. Resultatene skal brukes for vurdering av sikkerheten på liknende innretninger How to share and learn from experience of inspection of decommissioned jacket structures 2

Client benefits What is possible to learn and obtain?

Client benefits What is possible to learn and obtain? Relation between design premises and real conditions - Structural condition - Corrosion protection Increased knowledge related to offshore repair and reinforcement solutions Confirm condition of non-accessible areas (e.g. piles, bolts/fastners, clamps) Verify inspection findings from operation Sharing information via common database 4

Guideline for inspection of decommissioned offshore structures Purpose of guideline: - To establish a common approach for planning, execution and documentation Deliverables: - A technical report giving guidance for planning, execution and documentation - Describe how the data should be arranged in e.g. a database. 5

OLF project Development of Guideline - Organization Contract: OLF (Per Otto Selnes/Lars Petter Lundahl) The project is technically organised with a Technical Committee representing OLF: - Leader: Tor Inge Fossan (Statoil) - Participants: Atle Nøsen (BP) Michael Hall (ConocoPhillips) Alf Kristian Haugland (Gassco) Patrick Decoesemaeker (Total) - Observer: Gerhard Ersdal/Erik Hørnlund (Ptil) 6

OLF Project Tentative Schedule Activity no. Activity 1 Administration 2 Development of draft guideline Month from start project 1 2 3 4 5 6 7 8 9 3 Meetings and workshops 1) 2) 3) 4) 4 Finalizing guideline after external review 1) Kick-off meeting 2) 1 st Technical Meeting; DNV to present suggested framework of content of the guideline for discussion 3) 2 nd Technical Meeting; Discuss comments to draft guideline with the industry 4) 3 rd Technical Meeting: Presentation and discussion of final guideline 7

Draft Guideline Table of Content 1 General 1.1 Introduction 1.2 Scope 1.3 Objective and use 1.4 Structure of document 2 Terminology and definitions 3 Abbreviations 4 Areas to be inspected 4.1 Group A Structural Strength 4.2 Group B Corrosion 4.3 Group C - Inspection 4.4 Group D - Other 5 Information gathering 6 Selection of areas 6.1 Basis for selection 6.2 Workshop Selection of inspections 6.3 Documentation 7 Preparations and execution of inspections 7.1 Group A Structural Strength 7.2 Group B Corrosion 7.3 Group C - Inspection 7.4 Group D - Other 8 Post-processing of data 8.1 Group A Structural Strength 8.2 Group B Corrosion 8.3 Group C - Inspection 8.4 Group D - Other 9 Storage of data 9.1 Group A Structural Strength 9.2 Group B Corrosion 9.3 Group C - Inspection 9.4 Group D - Other 10 References 8

4 Areas to be inspected List all areas for inspection which is covered in guideline Each area for inspection has a dedicated designation/code which will follow this topic in each section of the guideline Group Area to inspect Designation A Structural strength Low fatigue lives A.1 Grout connection between leg and pile A.2 B Corrosion Evaluation of CP system B.1 Coating B.2 C Inspection Inspection findings C.1 Areas of challenging underwater inspection C.2 D Other Bolts D.1 Repair clamps D.2 9

Ranking of areas to be inspected Some inspections should be mandatory on all structures Cost/Benefit ratio Inspection ID Low Mandatory on all structures Medium If found relevant in workshop High Laboratory testing. If agreed in workshop 10

Draft Guideline - Illustration of Work Flow 4 Areas to be inspected 5 Information gathering A.1 A.2 B.1 C.1 C.2 D.1 6 Selection of areas A.1 A.2 B.1 C.1 C.2 D.1 7 Preparations and execution of inspections 7.1 Group A Structural Strength A.1 A.2 7.2 Group B Corrosion 7.3 Group C Inspection B.1 B.2 C.1 C.2 D.1 7.4 Group D Other D.2 9 Storage of results A.1 B.1 C.1 8 Post-processing of data A.1 B.1 C.1 11

6 Selection of Areas Cessation Project 1. Establish basis for selection of areas for inspection - Deliverance: Workshop package 2. Workshop to detail location and specify type of inspections 3. Include requirements to inspection in the decommissioning plan Shall bring in resources within structural strength, inspection and materials 12

6 Selection of Areas Example Check List ID code Description Purpose Comment Check list 13

OLF Project Development of Guideline SELECTION OF AREAS Cessation Project Bid and contract award for demolishing contractor INSPECTION Offshore removal Transport to yard Demolishing at yard STORAGE RESULTS 14

Overall project Phase 1, 2 and 3 50 Inspection of structures Guideline Collection of data Vision: Improve the basis for assessing the safety of similar structures Design Premise Inspection Findings Design analysis and comparison Phase 1 Phase 2 Phase 3 15

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