The company said, however, that the Gladstone project’s economics remained strong, even in low oil prices.

“The impairment of Origin’s upstream oil and gas assets reflects recent reserves revisions, as reported in Origin’s Annual Reserves Report, revised development plans and lower oil prices,” the company said.

“The impairment charge is in addition to the $53 million impairment charge of New Zealand onshore assets announced in the 2015 half year results.

“There is no impairment related to Australia Pacific LNG, the economics of Origin’s investment in Australia Pacific LNG remain robust.”

The biggest hit for Origin came in the Cooper Basin, where a revised operator development plan, reserves revisions and lower oil prices led to the company booking a post-tax impairment of $180 million.

The impact of reserves revisions and lower oil prices also led Origin to post-tax impairment of $122 million in the Bass Basin and $35 million in the Otway Basin.

Origin’s impairment analysis was based on Brent oil price estimates that were consistent with FY16 forward prices stepping up to $US80/barrel from the 2020 financial year.

APLNG, an incorporated joint venture with US major ConocoPhillips and Sinopec, is one of Australia’s largest CSG to LNG projects based on the country’s largest 2P CSG reserves base.