Gorgon’s carbon capture shortfall

The self-described “world’s largest carbon capture and storage project” hasn’t captured enough carbon to meet its goals. The Gorgon LNG Project, a large-scale gas-mining project off the West Australian coast, has not been able to capture 80% of the carbon dioxide it has emitted over the past five years – a target on which its initial state government approval depended.

According to analysis by independent energy journalist Peter Milne, the plant (which is run by Chevron, with energy companies Shell and Exxon holding large shares) has only stored 30% of the CO₂ it produced over the five years between 18 July 2016 and 18 July 2021.

So what was supposed to happen, and what went wrong?

Methane gas reservoirs often contain carbon dioxide as well, meaning that mining of liquefied natural gas (LNG, or methane gas) emits carbon dioxide. This makes it an emissions-intensive venture before the methane itself is combusted for energy.

Carbon dioxide is separated from LNG during processing and purification. This CO₂ is usually vented into the atmosphere, but as part of the project’s environmental approval, granted in 2009, Chevron was required to build infrastructure that could remove and store all of the carbon dioxide in the gas-production process. 

Over a five-year rolling average, Chevron would also need to ensure that at least 80% of the carbon dioxide produced in the LNG purification was prevented from getting into the atmosphere. The simplest way for it to do this was to inject the CO₂ deep underground.

According to Professor Peter Cook, of the Peter Cook Centre for Carbon Capture and Storage Research at the University of Melbourne, this is a practice that has been used commercially for several decades, although not yet on the scale of Gorgon.

“You get your CO₂, you compress it to what’s called supercritical CO₂, which means it’s dense, it’s like a fluid,” explains Cook.

This dense fluid is then pumped into the earth, aiming for specific rock formations that can hold it. “At about 800 metres deep, the pressure is equivalent to supercritical pressure, so if you inject this liquid-like CO₂ in the subsurface, it remains in a liquid-like state,” Cook says.

In Gorgon’s case, the CO₂ was headed more than two kilometres beneath Barrow Island, about 1400 km north of Perth off the Pilbara coast.

“People say, ‘well, why doesn’t it escape anyway?’ And the answer is, it doesn’t,” says Cook.

“In some cases it will react with the rocks. More commonly, the rocks are fairly quartz-like or quartz-rich. They’re not very reactive, so it fills the pore space.”

Around 20–30% of the rock at this depth is actually space, which the liquid CO₂ can fill up.

“It is a complex process, so you have to get the technology right,” says Samantha Hepburn, a professor of mining, energy and environmental law at Deakin University.

“The issue with Gorgon, I think, is that they just haven’t got the technology right and they’ve been given a lot of dispensation.”

The Gorgon plant began exporting LNG in mid-2016, but its carbon removal and injection infrastructure ran into technical difficulties, and did not begin operations until 2019. When running at full capacity, the project aims to inject four million tonnes of carbon dioxide per year, although as yet it’s not clear if it’s been able to reach this capacity.

Chevron hasn’t disclosed precisely why the infrastructure took so long to get running. In a statement, Mark Hatfield, Chevron Australia’s managing director, said that, “Chevron is working with the WA regulator on making up the shortfall and will report publicly on that later in the year”.

Cook says that while Gorgon’s technology is proven – pointing out the small scale Australian project in the Otway Basin and the much larger Sleipner project in Norway as examples – local environment makes a big difference to the viability of carbon capture and storage.

“Industry have been using this technology for decades: taking fluids out of the ground, putting fluids in the ground, understanding the rocks, and so on,” he says. “Having said that, you’ll always get surprises drilling wells down to two kilometres. You’re dealing with a difficult environment.”

Hepburn says that although carbon capture and storage is a necessary part of the path to net zero emissions, Chevron’s shortfall raises questions for the future approval of similar gas projects.

“If Chevron can’t get it right, with Shell and Exxon, then who’s going to get it right?” she asks. “Is it possible to get it right? I’m sure that it is, but it does take time, and the question is, do we have that time?”

Cosmos contacted Chevron for comment and a spokesperson reiterated that the company would meet the carbon removal target, although the details are still being worked through with the Western Australia government.

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Read more:

• Can we bury the carbon dioxide problem?
• Converting CO2 into everyday materials
• How does carbon capture and storage work?