Woodside Petroleum has reported a significant downgrade of proven total reserves at the Julimar-Brunello gas project off Western Australia.

Woodside said in its third quarter report that proven (1P) total reserves were down from 54.5 million barrels of oil equivalent to 11.5 million boe.

The project's proven plus probable (2P) total reserves are down to 26 million boe from 86 million boe.

The reserves have been updated after completion of reservoir studies based on 4D seismic, well performance and well drilling results, said Woodside.