Design for decommissioning

The final page will be completed soon with the addition of guidance on design for decommissioning of topsides, jackets and FPSOs

Statement of objectives

The D4D Database provides feedback from late life and abandonment operations.  It provides practical guidance to engineers when designing new facilities or modifying existing facilities

The challenges and issues encountered at the end of a facility's life may not be foreseen or correctly considered during the design phase. This lack of attention can make the eventual decommissioning work more technically challenging and costly.  The purpose of the database is to identify decommissioning issues based on real industry lessons learnt and translate these into potential solutions which could be implemented in future designs

History of JIP

Work group: formed in Aug 2016 with thirteen organisations.  By Febuary 2018 another  fourteen organisations had joined.  Work group has twenty seven active participants providing lessons learnt and mitigation solutions 

Initial project scope: boundaries identified – i.e. subsea only

Demonstrated economic value: examined the influence of decommissioning costs in the whole asset lifecycle

Structure for database: defined for use by Lead Design Engineers

Database populated: input from decommissioning community as follows

• One on one interviews lasting about one hour with all members of the JIP gaining their experience in the UKCS, Africa, Norwegian and Australian waters. • Attendance at the decommissioning conferences o Decom North Sea, o Oil and Gas UK, o Norwegian Petroleum Forum, o SE Asia Kuala Lumpur, o SPE workshop Kuala Lumpur o Decom World Houston o Decom World Aberdeen • Review of the Lessons learnt of BP when doing decommissioning projects in the North Sea over the last five years • Reading the technical press (Offshore Engineer and SPE journal during the last two years)

Industry guidelines: started preparation to integrate findings and recommendations into the conceptual and FEED phases of the lifecycle

Decommissioning cost matrix

The guidance note maps the decommissioning requirements back to the infrastructure components in a series of design considerations.

It will provide a framework to incorporate decommissioning requirements into the design process and include a set of templates and checklists

The relative cost of decommissioning each component of a subsea development has been assessed and is listed on the table.

A series of activitiies are needed to decommission and remove each component.  These activities have been listed in the table.  The activities are taken from the list of decommissioning activities published in the Oil and Gas UK guidelines.   The cost of an activity to decommission a component of the subsea development has been assessed as being

• High (coloured red),
• Medium (coloured yellow)
• Low (coloured blue)

Decommissioning activites that are not applicable to a component have been left blank

When to incorporate decommissioning in design

Decommissioning shuold be incorporated in the design during the Define or FEED stage of the project.  This is the stage of a project where the major design criteria are written in to the Basis of design and design specifications.  After this stage the project  team has moved to the Execute stage  and Change control is rigoursly enforced.  Modifications to the design to assist or ease decommissioning will not meet the criteria for the change control committee. 

Before the Define or FEED stage the project team will be studying several options to select the best solution to develop the field.  There is not enough definition of the options to consider design for the final decommissioning.  The decommissioning specialist should provide an estimated cost of decommissioning and remvoing each option for the project cost estimates and list the removal options and any issues for the regulators and other stakeholders.

Database of lessons learnt and design guidance

Rigid export pipelines

Flexible risers

Pipeline bundles

Manifold and riser bases

Wellheads

Umbilicals

Flexible pipelines

Economic Benefits

The cost of decommissioning can affect the project economics.  Project economics use the Net Present Value calculation.  This calculation needs the Capex, Opex, Decommissioning Cost or Abex, tax rebate and income from sales of oil and gas.  Economic analysis has been completed for the Clyde project reported  in the Offshore Europe conference in Aberdeen in 2017 (Design for Decommissioning) 

Noteworthy Papers in OnePetro

Stokes, A. W. 2014. Decommissioning Costs Can Be Reduced. Offshore Technology Conference. https://doi.org/10.4043/25247-MS

External Links

Decom North Sea L2P2 http://decomnorthsea.com/l2p2 

Contacts

Stuart Martin Stuart.Martin[AT]ardent.com

Caroline Laurenson Caroline.Laurenson[AT]xodus.com

Alan Stokes Alan.Stokes[AT]advisian.com

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