Starting in 2014/15, Chevron will begin injecting 120 million tonnes of pressurised supercritical carbon dioxide 2.5 kilometres underground as part of its giant Gorgon LNG project.

Raw gas from the Gorgon field contains about 14 percent carbon dioxide (CO2), which must be separated out and safely disposed of before the purified methane can be liquefied and sold.

Under an ambitious programme agreed with the state and federal governments back in 2009, Chevron will inject the CO2 into a saline aquifer beneath Barrow Island off the coast of Western Australia.

Chevron is spending $2 billion on the world's largest CO2-injection facility, which will store over 3 million tonnes per year, making it by far the world's largest CO2 storage project, and creating a unique opportunity to study how injected CO2 behaves underground in saline aquifers.

LONG-TERM INDEMNITY

Barrow Island is a Class A nature reserve and carbon dioxide is fatal to humans in concentrations as low as 7-15 percent. So Chevron has conducted extensive seismic surveys and drilling to estimate the aquifer's storage capacity and ensure it will not leak.

The company has also promised to monitor the underground movement of the CO2 plume as it spreads away from the initial injection wells using 4-dimensional seismic surveys.

Together with its joint venture partners, Chevron will be responsible for any costs associated with leaks and other damage duration the lifetime of the project and for 15 years after CO2 injection ceases.

But the Commonwealth of Australia and the State of Western Australia have agreed to accept responsibility for any long-term liabilities. Commonwealth and state indemnities will protect the joint venture partners from any common law liability arising from third party claims for loss or damage, suffered after the site closes.

The indemnity will only occur after continuous monitoring and modelling of the stored carbon dioxide for at least 15 years after injection ceases, and when both state and commonwealth governments are satisfied the CO2 has been stored safely. It is not expected to become effective for at least 75 years, according to an analysis prepared by law firm Baker & McKenzie.

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Source: by John Kemp, Reuters, 10 September 2013