UPDATE 1-Woodside restarts Cossack-Pioneer oil field

(Adds details on BHP's and Santos' operations)

SYDNEY, Jan 4 (Reuters) - Woodside Petroleum Ltd (WPL.AX), Australia's second-largest oil and gas producer, said on Friday production at its Cossack-Pioneer oil field off Western Australia has restarted after a cyclone threat passed. The Cossack-Pioneer field, which has an approximate production rate of 73,000 barrels per day (bpd), was restarted overnight after a near one-week-long shut down, said Woodside's spokeswoman Laura Hammer.

Output at Woodside's 50,000 bpd Enfield oil field off Western Australia restarted on Dec. 31.

Santos Ltd (STO.AX), Australia's third-largest oil and gas producer, said output at its Mutineer-Exeter field resumed late Wednesday after ceasing operations on Dec. 29.

The field, which had a daily production of about 55,000 barrels, saw its output plunge to between 4,000-5,000 barrels after an electrical outage damaged its sub-sea pumps.

But BHP Billiton, Australia's largest oil and gas producer, said its 10,600 barrels per day (bpd) Griffin oil field was still shut in as rough seas were preventing the production vessel from sailing back to location and reconnecting to the field.

"We are still monitoring the weather and we're also outwatching the cyclone that may form in the northern coast," said BHP's spokeswoman Emma Meade.

A second cyclone is expected to form off Australia's northern coast over the weekend, the weather bureau said on its Web site. (Reporting by Fayen Wong)