A sunken gas tower off the coast of Western Australia needs to be immediately removed by oil and gas company Woodside, according to environmental activist group Greenpeace.
Greenpeace CEO David Ritter said footage shot by the group showed the tower "decaying" and demonstrated the "sheer arrogance" of both Woodside and BHP, who owned the tower when it sunk.
"You have to suspect that when something the size of an apartment block has just been left on the ocean floor to corrode ... that it's just been forgotten and that the company is hoping that it's out of mind, out of sight," Mr Ritter said.
"This is part of a systemically important issue for the oceans and for the oil and gas industry. We're talking about a multi billion dollar decommissioning liability of the oil and gas industry that they're not properly facing up to."
The 93-metre-tall structure, called a riser turret mooring (RTM), sank back in 2013 when it was under the ownership of BHP Petroleum.
A riser turret mooring is a structure anchored to the ocean floor, and brings the subsea gas lines together to the surface. A ship with a specialised docking device is able to attach itself to the mooring where it can load hydrocarbons (such as oil and gas).
This particular RTM is sitting in what Mr Ritter describes as a "fantastic bit of ocean off Western Australia", about 94 kilometres from Exmouth in the Griffin field, at a depth of around 120 metres.
Gas production in the Griffin field stopped in 2009, and the wells were permanently plugged in 2017.
Six buoys were removed in 2018, but in 2021 offshore oil and gas regulator NOPSEMA directed BHP to completely decommission Griffin field or face fines.
BHP's oil and gas portfolio merged with Woodside soon after in mid 2022.
NOPSEMA has given Woodside until the end of 2024 to remove the sunken structure from the Griffin field, however Mr Ritter said Greenpeace was sceptical of Woodside's intention to clean it up.
"Woodside has a history of not doing what NOPSEMA asks in terms of cleaning up its mess," Mr Ritter said.
In 2021, NOPSEMA took compliance action against Woodside due to the company being "unable to comply with an originally approved plan to remove equipment for onshore disposal".
In that case it was the Nganhurra riser turret mooring in the nearby Enfield field, which has also shown signs of instability.
"Due to the equipment's poor condition and repair, this is no longer feasible without unacceptable risks to safety and the environment," NOPSEMA said in a statement at the time.
Woodside's revised plan for the Nganhurra RTM is to sink it to make an artificial reef, according to a NOPSEMA report from 2021.
Further compliance action possible
In response to questions from the ABC, a NOPSEMA spokesperson said potential contaminants in the sunken Griffin RTM include two compartments that contain high-density and low-density polyurethane foam, plus some plastics and an epoxy coating.
However, the spokesperson said the risk of contamination at this stage was low.
"The RTM structure remains largely intact on the seabed so presents a low risk of contaminating the environment in the short to medium term, as the foam is contained within the structure," the spokesperson said.
"Several risers, umbilicals and well-services lines also extend through the RTM structure. The risers, umbilicals and well-services lines have all been flushed free of [oil and gas] and are now filled with seawater."
NOPSEMA said it may take "further compliance and enforcement action" if Woodside failed to meet its removal requirements.
A spokesperson for Woodside said the company was confident the sunken RTM wouldn't negatively impact the marine environment.
"Woodside has performed visual inspections that have confirmed the integrity of the RTM and undertaken studies to analyse the contents of the structure. These studies demonstrate that the contents do not have any adverse impact to marine life."
"Woodside is currently finalising a competitive tender process for the removal scope of work, with planned removal of the Griffin RTM before the end of 2024 in line with regulatory time frames."
The spokesperson also said work has been done to the Nganhurra RTM to improve its buoyancy.
Greenpeace's David Ritter said any failure of Woodside to clean up their gas infrastructure would set a dangerous precedent.
"We're concerned about the the current infrastructure that's yet to be cleaned up, but also the infrastructure that will need to be cleaned up as the world inevitably turns away rapidly from oil and gas."
