Case Study - 3 Sci

3 Sci Accelerated Corrosion for Decommissioning

The accelerated corrosion technology will allow subsea installed steel structures and pipelines to be dissolved in-situ as a means of permanent decommissioning of uncoated steel jackets or manifolds submerged in seawater.

Other subsea steel structures, including pipelines, can also be considered as candidate ‘targets’ for this new technology.

The analyses to date suggest significant cost savings could be possible in decommissioning, as compared say, to the use of conventional heavy lift methods. The accelerated corrosion technique also looks likely to provide environmental benefits through significant reductions in greenhouse gas emissions.

Scaling of the results indicates that a 10,000t large steel Jacket could be dissolved in 3 years using a 5 MW offshore wind turbine as its power source. Monitoring systems on board the tending barge would record the dissolution process to ensure maintaining the desired settings of the electrical power supply and record the rate of metal loss caused by the accelerate corrosion devices.

 

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Figures: Left: Dissolution of a steel tubular by accelerated corrosion during workshop trials. Right: example of a potential subsea layout of devices for application to steel jackets.


Phase 2 of the testing to date has conducted larger scale tank trials.

Initial data have provided very promising results on mild steel, using approximately 1 KW-hr per kilogram of steel dissolved (In seawater). The technique has also been proven in workshop trials on other metals.

The next testing phase, ‘Phase 3’, will be an open water sea trial on appropriate structures to help prove some of the underwater devices and underwater techniques that shall be employed. The Phase 3 open sea trials will also quantify more precisely, the various environmental impacts of the approach.

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