In the latest EnergyQuarterly report released by energy economics consultancy EnergyQuest, oil production was found to have plunged from 27.3 million barrels in the December 2010 quarter to 20.9MMbbl in the March quarter.

"Australian oil production is on a long-term downward trend due to natural decline in mature fields. However, there were also a number of one-offs in the latest quarter," EnergyQuest chief executive officer Dr Graeme Bethune said.

He noted that in the northwest the cyclone season was more intense than usual, while a number of fields were interrupted for maintenance and North West Shelf output was shut-in from early March for redevelopment.

The Woodside Petroleum-led North West Shelf Venture is currently awaiting the converted Okha floating, production, storage and offloading facility to replace the Cossack Pioneer FPSO as part of the $1.8 billion NWS oil redevelopment project.

The NWS is also currently carrying out the $5 billion North Rankin redevelopment project that is aimed at recovering the remaining low-pressure reserves at the North Rankin and Perseus gas fields.

This is expected to extend field life to about 2040.

Bethune said in the longer term the NWS redevelopment would extend the life of one of Australia's most important oil fields.

He added BHP Billiton and Apache went against the national trend due to the good performance of their Pyrenees oil field, which started production last year.

"There was good news too on the exploration front, with successful drilling by Woodside, with partner Mitsui, in the Laverda (also WA) oil field, which has lifted expected recoverable oil volumes to over 100 million barrels."

The report also found that while quarterly liquefied natural gas production was flat, the imminent start-up of Woodside's Pluto LNG project would see an increase in LNG production next year.