Environmentally Friendly Subsea Pipeline Decommissioning

Fielder, Daniel (Allspeeds) | McGarry, Rory (Allspeeds)

OnePetro 

Abstract Objectives/Scope

Subsea pipeline decommissioning for either abandonment or retrieval is hazardous for both divers and the marine environment. This presentation reports on the development of a Fast Intervention Tool (FIT) for pipeline decommissioning by Webtool with input from Chevron Energy Technology Company. The FIT reduces the risks to divers and enables a quicker operation while avoiding the need for a containment dome during pipeline cutting and retrieval.

Methods, Procedures, Process

Sophisticated measures are taken to reduce the hazards to divers and the impact on the marine environment during pipeline decommissioning. Yet, traditional cutting technologies can undermine these best intentions. Diamond wire or other types of saw are time consuming and prone to jamming as the pipe moves during the cut. The containment dome used to catch contaminants that leach out during cutting and retrieval cannot "follow" the pipe as it is retrieved via a crane, therefore additional measures are needed to plug or seal to the pipe end before retrieval. The Fast Intervention Tool presented here addresses these shortcomings.

Results, Observations, Conclusions

The FIT combines lifting, crimping, injection and cutting in a single deployment frame which also contains the hydraulic control system. Deployed using a barge crane, the FIT assembly is lowered over a pipeline on the seabed, with either a diver or ROV to position it. The FIT cycle time to lift, crimp, inject sealant and cut is under 1 hour (excluding vessel or set up time) after which the pipe can now be safely recovered topside without leakage. The spike injector and blades will perform a number of cycles, therefore running costs are low; the only major consumable cost is the sealant itself. Webtool has completed FIT conceptual design and in-house development and testing and is now preparing a working prototype for hyperbaric and sea trials.

Novel/Additive Information

Safer and more environmentally friendly method of pipeline decommissioning.