Closure decisions are often won or lost at the interfaces

1. Describe the end state in observable terms

“Decommissioned” is too broad to serve as a completion criterion. Describe what has been removed, what remains, the condition of anything retained and the evidence required to demonstrate that condition. Keep physical completion, completion of a contract and a regulatory decision as separate milestones.

For Commonwealth offshore petroleum, NOPSEMA describes full property removal as the base case. Alternative approaches need the relevant demonstration and applicable requirements addressed. An option study should therefore state its permissioning assumptions explicitly, rather than treat a potentially lower-cost end state as available by default. NOPSEMA decommissioning overview ↗ (opens in a new tab).

2. Follow each item across the boundary

Trace a representative item from its present location to its final destination. That journey can cross operating systems, isolation boundaries, temporary works, lifting and transport arrangements, port access and a receiving facility. At each handover, identify the incoming condition, outgoing condition and evidence passed with the item.

A removal package may assume that equipment is clean enough for transport while a waste package assumes that decontamination will happen offshore. Both packages can look complete when read separately. A boundary review exposes the missing task. The same reasoning applies to survey coverage, pipeline ends, subsea debris and the records that demonstrate well work has been completed.

3. Align contract completion with evidence completion

Create an interface register before procurement. For each boundary, record the supplying party, receiving party, acceptance criteria, dependency, decision owner and required record. Include the assumption that would force the handover to be redesigned. Where an outcome depends on a third-party facility, establish what information that facility needs to decide whether it can receive the material.

The engineering task is to make these conditions explicit. The applicable transport, waste, environmental, safety and offshore requirements depend on the actual route and jurisdiction. A single offshore permissioning document should not be assumed to settle all onshore obligations. The government's Roadmap discusses decommissioning as a value chain that includes materials management and onshore capability. Australia's Offshore Resources Decommissioning Roadmap ↗ (opens in a new tab).

4. Plan the closure evidence before execution

Decide in advance which observations, inspections, surveys and records will demonstrate the required end state. Otherwise, the project may discover that an area is inaccessible or a component has been disposed of before necessary evidence was captured. A well-defined evidence requirement also gives contractors a more useful completion test than a general promise to provide a final report.

NOPSEMA's Section 270 policy addresses property, wells, natural resources and seabed or subsoil condition in its advice on title surrender. It notes that compliance with accepted permissioning documents is a primary means of demonstrating the relevant matters, but is not an assurance of NOPSEMA's satisfaction at surrender. Section 270 policy ↓ (opens in a new tab).

A practical close-out review reconciles the asset inventory, work completed, approved variations, remaining obligations and evidence still outstanding. Every residual item should have an owner and a defined next decision. That creates a usable account of progress without compressing several different kinds of completion into one green status.