After 20 to 30 years of extraction, rigs usually stop functioning as technical failures or high costs make their operation unsustainable. Transitioning away from fossil fuels is expected to accelerate this process.

But what happens when they're decommissioned?

Closing the well and removing all infrastructure in a way that limits hazardous leaks and environmental damage can cost operating companies up to €500 million per rig and requires massive logistical operations.

International conventions such as OSPAR, which applies to the North-East Atlantic, require those platforms to be removed completely to allow safe navigation and safeguard the marine ecosystem. Authorised exceptions are increasingly difficult to obtain.

This April, the North Sea Transition Authority fined UK operator EnQuest £16.5 million (around €19 million) for repeated delays in closing its disused wells. In 2025, the Authority warned that 500 wells missed their decommissioning deadline, and that “operators are running out of time to get to grips with the backlog”.

Rigs-to-Reef

There's a growing argument against removing rigs at all: when concrete infrastructure remains in deep waters for decades, it becomes part of the natural habitat. The Rigs-to-Reef option consists of letting rigs be part of the ecosystem.

Research suggests rigs attract fish, invertebrates, and algae, becoming havens for marine biodiversity. This was noticed, for example, right off the Dutch coast: the Halfweg platform was scheduled for full removal, but after a vessel damaged it in 2017, part of the structure was left on the seabed.

A 2020 study found that the structures became home to 65 species, some of which were unique to the platform and absent from the surrounding seabed.

Italy is trying it out: its latest law on sea resources, published this May, orders decommissioning projects to first assess the marine ecosystems formed on the platform while it was operating.

Since Rigs-to-Reef costs half the price of full platform removal, Italy's new regulation was criticised as “a gift to oil companies”.

Umberto Mazzantini, member of the environmental organisation Legambiente, told us that companies should be held accountable for past pollution before claiming environmental benefits.

No one-size-fits-all

The problem with both approaches is that we don't know much about rigs' ecological effects. Globally, only 42 peer-reviewed articles document the environmental impact of decommissioning, with no common standard to compare different options.

Dr Anaëlle Lemasson, Research Fellow at the University of Plymouth's School of Biological and Marine Sciences, explained that we need a lot more research. “But this must not justify lack of decisions. We need to have a look at what we already know and try to figure out what the best possible outcome is,” she told us.

Rigs-to-reef solutions risk leaking contaminants as they corrode, altering the natural ecosystem structure, and attracting invasive species. But Lemasson said full platform removal also has its downsides, such as disturbing sediment, massive transport emissions, loss of endangered species, and disruption of the newly formed habitat.

Turning installations into artificial reefs doesn't always work. Ecosystem growth varies hugely between structures, Lemasson noted, even within the North Sea. Some attract dense, diverse colonies, others almost nothing.

The researchers we spoke to agree that decisions need to be made case-by-case. Dr David Peterson, from the University of St Andrews' School of Biology, suggests criteria: “Where is it? How valuable is it in terms of the species it harbours? What are the risks of removal versus leaving it in place?”