Shares in Woodside Petroleum slumped six per cent to a seven-week low after the oil and gas producer’s 2012 production target fell short of expectations.

Woodside announced in an investor update that it was targeting a 27 per cent rise in production in calendar 2012 when the first stage of its Pluto liquefied natural gas (LNG) project begins operations.

The company affirmed previous advice that first cargoes from Pluto would occur in March.

However, the forecast did not meet analyst expectations, CMC Markets chief market strategist Michael McCarthy said.

Woodside provided full year production guidance of 73 to 81 million barrels of oil equivalent (MMboe), well below analyst estimates of 85 to 90 MMboe.

Of that, 17 to 21 Mmboe would come from Pluto.

Analysts had been tipping 26 to 30 Mmboe from Pluto.

Mr McCarthy said the style of Woodside’s new chief executive Peter Coleman appeared to be under-promising and over-delivering, so he suspected the company would perform better than forecast.

“I’d suggest he’s just being conservative,” Mr McCarthy told AAP.

The shares closed down $2.06, or 5.8 per cent, at $33.36, the lowest since October 5. More than 11 million shares in the Perth-based company changed hands, the most in two weeks.

Reflecting on the relative cheapness of Woodside stocks, which were more than $66 each in mid-2008, Mr McCarthy said it was interesting to note the company had not been targeted for a takeover as widely expected.

Speculation that BHP Billiton, which has a substantial petroleum division, was poised to make a bid for Woodside reached fever pitch in April.

Even Western Australia’s premier Colin Barnett weighed in to the talk at the time, saying “hands off Woodside” at an oil and gas conference in Perth.

Woodside’s biggest shareholder and joint venture partner, Royal Dutch Shell, offloaded part of its interest last year.

Mr Coleman last month said Shell was in no hurry to sell its remaining stake.