The savage slump in oil prices has exacted a heavy toll on Woodside Petroleum, with its full-year net profit tumbling 99 per cent to just $US26 million ($36.6 million).

It is a massive reversal of fortune from last year's $US2.4 billion result and the record $US3 billion profit reported just three years ago.

Revenues decreased by $US2.6 billion to $US4.5 billion, a result almost entirely driven by lower prices.

Woodside said realised prices for oil, condensate and LPG were driven down in line with the 46 per cent decline in the Brent crude benchmark price.

The North-West Shelf and new Pluto LNG fields had their realised price slashed by 40 per cent due to a collapse in Japanese gas pricing.

Gas and liquid volumes fell marginally by 0.5 MMboe (million barrels of oil equivalent) from last year's record production to 92.7 MMboe.

However, this only had a smaller $US120 million impact on the bottom line.

Woodside's chief executive Peter Coleman said the company is looking at all of its investment decisions, but it is too early to say how quickly oil and gas prices might recover.

"What's not clear to me today is are we in the middle of a fundamental structural change in the industry or is this just a short term disruption, where we'll go back to long term trends in a relatively short period of time," he said.

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Woodside also announced that impairment charges - asset value write-downs - increased by $US649 million, largely as a result of forward price assumption which was wound back by 20 per cent from 2014 assumptions.

Overall impairments were booked in at $1.1 billion, with the charge against the 65 per cent complete Wheatstone project rising to $US865 million.

Woodside was forced to cut its full year dividend by 57 per cent to $US1.09 ($1.53) which was ahead of many analysts' expectations.

The company's shares were smashed on the ASX, falling 6.4 per cent to $27.66 by 1:20pm (AEDT) in a generally rising market, and easily exceeding the declines for rival oil and gas producers.