The Challenge
An operator made the decision to remove an FPSO in the North Sea and decommission the associated infrastructure. A scope of work within this decommissioning project was the cutting of the subsea riser.
The operator approached Aubin as they required a sealing compound to create an environmental barrier when cutting the associated risers prior to recovery at a later date.
The ultimate goal was to ensure the plug would create an excellent seal to ensure there was no bypass of hydrocarbons into the environment.
Prior to the offshore operation, onshore testing of the methodology and application was completed successfully.
What Happened?
The Aubin team proposed AXI-Lokk, a product from the Integrity range that provide a temporary or permanent barriers.
AXI-Lokk is a silicone elastomer that provides an inert plug once cured, preventing any potential seepage of hydrocarbon out of the riser once cut.
This product is supplied as a 2-part liquid mix, whereby the activator is added into a base. Mixing these two components initiates a cross-linking reaction eventually causing the product to solidify into an elastic plug.
During the period while the product remains liquid AXI-Lokk was pumped into the top of the riser. Being hydrophobic and lighter than seawater AXI-Lokk formed a distinct layer above the seawater in the riser. The product was left for around 12-24 hours to successfully cure and create a tight solid plug within the riser.
As mentioned, the curing time for this specific project was around 24 hours, however, this can be altered in the development stages to meet the specific project requirements.
The Result
AXI-Lokk CW was deployed successfully into the riser and cured exactly in line with design expectations confirming its suitability for this type of subsea application. The AXI-Lokk managed to fill every single groove creating a very reliable seal and ensuring no hydrocarbons were released.
The client was extremely happy with the end result, subsequently the operator managed to efficiently and safely cut the riser and it will be recovered from the seabed at a later date.
