Decommissioning of disused oil & gas facilities are big business around the world as a lot of fields are becoming depleted and the authorities demand that all infrastructure, above and below surface, are removed and the seabed returned to it’s original condition.

Plugging and abandoning wells to ensure there will be no leaks in the future is important.
Doing so cheaply and efficiently has become challenge especially sub sea wells in deep waters. This usually requiring full size drilling rigs and can take weeks and months to complete.
Special riser less methods have been developed to allow smaller and cheaper vessels to perform this task:

Removing platform topsides and jackets has been done by cutting and lifting. This is costly, time consuming and represent a safety risk.
Allsea’s Pioneering Sprit can reduce both cost, time and safety risks by lifting and transporting heavy topsides and jackets in one piece:

Unfortunately the P.S. cannot be used in the GoM due to local restrictions on foreign vessels transporting recovered topsides or jackets to a US port for demolishing.
The alternative would be to do the demolishing in some other nearby country, or i

Decommissioning in the GoM:

Helix goes shallow water: