Client: Confidential

Decommissioning Cost Estimate (DSA)

Location: United Kingdom

Value Added by Xodus

When approached by our client to support a revalidation of their field Decommissioning Security Agreement, Xodus curated an integrated team of wells, subsurface and surface experts to look at all aspects of the proposed decommissioning programme. Xodus’ solution lead approach resulted in a number of risks and opportunities being identified and ranked, which were then supported by high-level decommissioning methodologies and cost estimates helping our client to make better informed and accountable decisions.


Xodus were asked by their Client to provide services and project management to support a revalidation of their field Decommissioning Security Agreement (DSA). The primary objectives were to:

+ Complete high‐level revalidation of scope for decommissioning activities associated with the fields,
+ Complete high‐level revalidation of the decommissioning programme timelines and project plan,
+ Complete high‐level revalidation of costs identified for decommissioning of the fields,
+ Identify critical activities that would need to commence in the next 2 years, assuming a COP of 2026,
+ Identify any errors or omissions or additional relevant information apparent from review of the DSA Report or from the completion of the revalidation exercise.


The Client requested a validation study of the Decommissioning Schedule and Budget Report that was completed by the previous field operator to provide assurance that the report was fit for purpose. A further objective was to revalidate the costs and timelines detailed in the report to ensure that any decommissioning requirements could be incorporated into future plans and strategy development. The scope included:

+ 3 bridge-linked platforms

›  a production utilities and quarters platform with accommodation for up to 168 persons (9,400 tonne jacket with 18,300 tonnes cellar deck and topsides modules);
›  a drilling platform (8,000 tonne jacket with 7,300 tonnes topsides modules); and
›  a reception / compression platform with gas compressor facilities;

+ 2 subsea fields tied back to the main complex;
+ 26 platform wells and 18 subsea wells;
+ 5.8km, 32” gas export pipeline including pig trap and isolation valves;
+ 248km, 24” oil export pipeline including pig trap and isolation valves;
+ 5.7km, 44” pipeline bundle including towheads, pig traps and isolation valves.


+ A small team of specialists was able to look at all aspects of the proposed decommissioning programme and identify early preparation activities, alternatives to reactivation of the existing drilling facilities and priority decommissioning activities;
+ Industry knowledge of decommissioning project planning and execution supported a critical review of the proposed programme;
+ High level risks and opportunities were identified and ranked;
+ High level decommissioning methodologies and assumptions were prepared to support the time and cost estimates. These provided a valuable base-case on which to develop subsequent plans.

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