Old Oil Rigs: Would It Be So Bad to Leave Them in the Sea?

It is a current dilemma if old sea oil rigs should be left in the sea or not, and the merits of leaving them are being discussed, including economic, environmental, and social benefits. 

Leaving Artificial Structures at Sea

The decommissioning of the offshore gas and oil infrastructure of the UK will cost 24 billion pounds in taxpayer money, as estimated by HMRC.

Is it worth removing and recycling human-made structures that have outlived their usefulness in the sea? It would save the public a lot of money. Three considerations are involved in the debate: if it would pass the test of sustainability in terms of society, the environment, and the economy.

To decommission an oil rig can be a tremendous effort. These offshore infrastructures have drilling and processing equipment on the surface and support structure from the seabed to the surface below it. 

The latter is usually a frame made of a steel jacket that is piled into the seabed. UK's most massive steel jacket belongs to the Magnus oil platform, weighing 30,000 tons, which is equal to the weight of 20,000 cars.

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Removing the Rig

Two stages are usually involved in the removal of rigs. The first stage consists in removing the surface equipment, which is cleaned and dismantled and lifter by crane barges. For the more massive topside structures, the operation uses double-hulled tankers.

After the top equipment is already removed, cutting of the jacket commences, and they are then also lifted to a barge, with both jacket and topsides brought onshore to be dismantled and recycled.

The rig's gas and oil wells have to be plugged as well, to avoid leaking the hydrocarbon reservoir's contents to the water and surroundings.

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Leaving Them Be

There is an increasing body of evidence that points to environmental benefits being reaped from just leaving these structures as they are.

The Gulf of Mexico US program known as Rigs to Reefs has already converted 532 gas and oil platforms and made them into artificial reefs. Many years being left in the sea causes epifaunal organisms to cover the structures. These include various bivalves and other animals, such as mussels, oysters, barnacles, sponges, corals, and tunicates.

They make the surface amenable for use by various marine life like worms, crabs, blennies, and sea urchins. They then become the base organisms that subsequently provide or become the food of larger fishes, until the structure finally turns into a real reef ecosystem.

The Scottish Wildlife Trust also agrees. Off Scotland's coast are structures that become the hard surfaces onto which hydroids, anemones, bryozoans, mussels, sponges, corals, and barnacles cling and colonize. They turn into shelter and breeding areas for fishes, attracting marine mammal predators.

Destruction by Decommissioning

To decommission the rigs, however, means destroying the thriving sea and ocean ecosystems that have been established in the area over the decades of the rigs' operations. 

There is also an increase in harmful air pollutants that include greenhouse gases, due to the enormous marine transport traffic necessary to remove the various sections of the rig.

There are also little economic and social benefits to rig decommissioning, creating few jobs in onshore recycling and dismantling operations. As an example, the removal of the Buchan floating facility only generated 35 new—and temporary—jobs. 

And in the end, decommissioning drains a lot of taxpayer money.

There is thus severe consideration, for the sake of economic, environmental, and social benefits, in abandoning old sea oil rigs as they are.

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