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Abandonment

At the end of viable production from subsea wells, an abandonment program may be required to render the well safe, remove the subsea infrastructure and return the seabed to its original condition.

 
The following operations and selected tools are typical of those encountered by an ROV team during this abandonment phase.
 

Vessel Campaign Pre-Rig Arrival

If the subsea well/field is old, then it is likely that detailed drawings and models will not be available. A seabed as built survey can be conducted using high resolution cameras, laser scanning and 3D acoustic imaging.
 

1. Conduct Video As Built Survey of the Field Using the Following TMT Tooling Options

2. High Pressure Cleaning of Subsea Trees and Manifolds

 

Rig Campaign

 

1. As Found Survey

2. Tree Cap Running Tool Landout

3. Tree Cap Testing

4. Unlock Tree Cap & Recover Tree Cap Running Tool

5. Clean Gasket Profiles / Tree Connector / Acid Caps & Calcium Wash

6. Clean Guide Posts / Connect Guide Wires

7. Run BOP / Tree Running Tool

8. Valve Ops / Inflow Pressure Testing (ROV) Intervention Skid

9. Disconnect HFL / EFL / FLOT & SIT

10. Connect IWOCS, HFL & EFL

11. Suspend & Kill Well

12. Disconnected Flowhubs / TMT Jacks / Gauges

13. Unlock SST Connector / Subsea Jacks

14. Recover Subsea Tree

15. Clean High Pressure Wellhead & Low Pressure Housing

16. Install Gasket

17. Deploy & Land BOP

18. Hook Up BOP Tensioning System / SST & Intervention Skid

19. BSR Test / High Flow BOP Skid

20. Flush Flowlines 

 

Subsea flowlines may need to be flushed prior to cutting and removal in order to prevent environmental contamination. Prior disconnection of the surface FPSO vessel makes it impossible to operate subsea manifold valves to carry out flushing back to beach or tank and in this case the Hot Tap Tool can be deployed to penetrate flowlines on either side of the manifold, connect high flow jumpers and safely carry out flushing operations.
 

21. Cut or Disconnect Flowlines

22. Cut Flowline Samples / HD Stills and Plug

23. Recover Guide Base

24. Cut Casing and Recover LPWH / HPWH

25. As Left Survey & Seabed Clearance Survey