Decommissioning of a North Sea Platform and Subsea Infrastructure

The Scope

Our client, a Southern North Sea operator, wished to flush and disconnect all flowlines and control umbilicals from each of the associated subsea wellheads and manifolds within a field.
The operation involved live well abandonment using a diving support vessel (DSV) to enable the well P&A activities and pipeline decommissioning/abandonment to progress separately.

The Solution

We were requested to provide specialist project engineering and project management by the operator for this scope of work, which included eleven wells, two manifolds, eight pipelines and nine umbilicals. Key activities were to:

• Manage mechanical intervention interface documentation.
• Liaise with OEM suppliers and vendors for offshore work.
• Review of contractor procedures for barrier testing of Xmas trees, manifolds and pipelines.
• Review of contractor procedures for wellhead and manifold intervention work.
• Provide offshore supervision and client technical representation for all diving operations including as-found surveys, barrier testing works, well intervention, implementation of MOCs, pipeline cutting and removal.
• Provide documentation to DECC related to the decommissioning.
  Provide bespoke solutions to problems with deteriorated Xmas tree hydraulic systems, umbilical flushing and barrier proving.

The Benefits

Our project engineering support and offshore technical representation gave our client assurance that the operation was continually supervised by a responsible and competent person and performed as per the agreed specifications.

Any issues arising offshore could be addressed immediately, ensuring efficiency and no chargeable vessel time was incurred. Our expertise made a significant contribution to a successful decommissioning project.