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:

Gyda Field jacket has been decommissioned by Pioneering Spirit:

Makes me feel old.
I was Towmaster for the towout of the Gyda jacket in 1989. Standing upright on the transport barge M-44 (LOA 600’ / 60000 DWT)
Seen here at loadout in Verdal, Norway:
Gyda 1 (3)
The jacket with slings and spreaders weight in at 8500 m.t. and stood 120 m. asl.

Under tow to the field;
Gyda 2 (4)
Yes there is a 600’ barge under the jacket.

Delivered under the cranes of the SSCV Micoperi 7000 (now Saipem 7000):
Gyda 3 (3) (390x492)

Lifted off the barge and set over a predrilled template on the seabed:
Gyda 4 (3)
This was the heaviest offshore lift ever performed at the time.

PS> Looks like the jacket has grown in weight since installation. (Maybe it’s inflation, or OE operate in Short Tons)

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There’s still money to be made in the shallow waters of GoM:

Even more money expected to be spent on decommissioning in the North Sea:

Decommissioning offshore oil & gas infrastructure is big business around the world:

PS> The first decommissioning jobs on the offshore wind industry has already been done, with more to follow as older/smaller turbines becomes obsolete.