Pipeline Removal vs. Leave-in-Place

The Challenge

The default outcome for offshore pipelines is decommissioning in place — over 97% of decommissioned pipelines globally have been left on the seabed after cleaning. That is not because leaving them is always preferable, but because conventional removal is slow, vessel-intensive and expensive enough to lose almost every comparative assessment on cost.

If removal is to be a genuine option rather than a formality in the option table, the cost and the environmental footprint of removal both have to come down — and the method has to be qualified well enough that a regulator and an insurer will accept it.

Our Approach

Removal only becomes a real option when it stops losing the cost criterion by an order of magnitude.

VORYX team members provided engineering leadership for a patented subsea pipeline removal technology, developed from concept through to third-party qualification. The design target was explicit: reduce vessel time per kilometre, because vessel time is what makes conventional removal uncompetitive.

Engineering covered the recovery mechanics — pipeline structural behaviour during retrieval, tension and bending control, seabed interaction, and the handling of spans, crossings and buried sections that defeat simpler methods.

The comparative assessment case was built alongside the technology: removal against leave-in-place on safety, technical feasibility, environmental impact, societal impact and cost, with the technology's performance evidenced rather than claimed.

Standards Applied

• OSPAR Decision 98/3
• Petroleum Act 1998
• OEUK CA Guidelines
• DNV-ST-F101
• DNV-ST-N001

Operator and project names are anonymised for confidentiality and disclosed on request. Experience described is that of VORYX team members.