* Cyclone risk off W. Australia revised to low
* Apache shuts two oifields as precaution
* Eastern grain areas to have heavier rain next week (Releads, adds more details on Apache operations, background)
By Jim Regan and Rebekah Kebede
PERTH/SYDNEY, Dec 16 Apache Corp has suspended oil production and evacuated workers from its offshore Legendre and Stag oil fields off the coast of west Australia due to a tropical depression in the Indian Ocean, the company said on Thursday.
Woodside Petroleum , which also operates offshore rigs in the vicinity and Rio Tinto , which uses coastal ports to export millions of tonnes of iron ore, said they were monitoring the low's progress as it heads slowly toward land.
Packing gale force winds, the depression could cause severe flooding south of Australia's Pilbara iron ore district. The storms was unlikely to intensify to cyclone strength, the Bureau of Meteorology said.
The Legendre field, which produces about 2,500 barrels per day (bpd) of oil, was shut on Wednesday night, while the Stag oil field, which produces 4,500 bpd, was shut this morning, company spokesman David Parker said. [ID:nL3E6NG088]
The shutdowns are standard operating procedure and the company is closely monitoring the weather, Parker said.
Two oil rigs contracted by the company, the Ensco 109 and the Stena Clyde, are still operating.
The Legendre field is located about 150 km north of the coastal town of Karratha. Stag is located about 60 km (37 miles) northwest of Dampier, one of two ports used by Rio Tinto to ship iron ore.
Officials at the Dampier Port Authority were not immediately available.
The Legendre facilities include the Ocean Legend, a mobile offshore production unit, and a floating storage vessel.
Stag employs conventional platform connected to another floating storage vessel.
Operations at Port Hedland, located roughly 250 km (150 miles) north of Dampier and used by BHP Billiton and Fortescue Metals Group to ship iron ore from the Pilbara, was so far unaffected by the low system, a port spokeswoman said.
The Pilbara coast experiences more cyclones than any other part of Australia. Since 1910 there have been 48 cyclones that have caused damaging wind gusts in excess of 90 kilometers an hour in or near Dampier, according to the Bureau of Meteorology.
At 0400 GMT, the tropical low was located 480 km (300 miles) west northwest of Exmouth and had a low chance of developing into a tropical cyclone through Saturday, but was more likely to remain a large monsoon low with gale force winds, according to the Bureau of Meteorology.
A low possibility means a 5-20 percent chance exists of the low becoming a cyclone. An earlier forecast gave the low a moderate risk of developing into a cyclone.
Another weak tropical low may develop off the Kimberley coast on Thursday, but had a low likelihood of developing into a tropical cyclone through Saturday, the service said
Cyclones off Australia's northwest annually force offshore oil and gas platforms to shut down temporarily.
These operations include the A$20 billion ($16.93 billion) North West Shelf venture, which is operated by Woodside in partnership with BHP Billiton, Chevron , BP Plc , Royal Dutch Shell (RDSa.L)(RDSb.L) and Japan Australia LNG (MiMi)Pty Ltd.
The region's cyclone season typically runs from November to April, though no cyclones have been reported so far.
Cyclones turn into rain depressions as they move inland across the northwest coast, sometimes disrupting iron ore mining in the Pilbara.
Rio Tinto and BHP Billiton are the two largest miners in the region, followed by Fortescue Metals and a handful of other miners.
Rio Tinto said in an email to Reuters that it was monitoring the weather situation at this stage, as is standard practice.
"But no disruption is expected at this stage," the statement said. BHP Billiton declined to comment.
The Bureau of Meteorology based its cyclone threat on computer modelling of the Madden Julian Oscillation index, which measures the tropical atmosphere over the Indian Ocean.
Australia faces almost double the number of destructive tropical cyclones, possibly as many as 22, across oil and gas, iron ore and sugar production regions during the 2010/11 cyclone season, the weather bureau said in October.
The largest increase in cyclones is expected off the northwest, with 11-12 cyclones predicted, compared with an average of seven.
The above-average number of cyclones expected off Australia's northeast and northwest coasts are a result of a strong La Nina weather system, which brings higher rainfall and more storms over the western Pacific.
La Nina has also caused unseasonably wet weather in eastern parts of the country, with floods hitting sugar production and also damaging the quality of what is on track to be a record wheat crop. [ID:nL3E6ND1UG][ID:nL3E6N80CU]
In sugar-growing districts of Queensland, possible showers are expected over the next few days with a minor risk of floods for the Fitzroy basin, the bureau of meteorology said.
Wheat districts in New South Wales are also expected to see showers up until Saturday, but from Sunday to Monday more substantial rains are forecast over the north east of the state, averaging arounds 40-50 millimetres over the two days.
Minor to moderate flood warnings remain in place across parts of Central West Slopes and Plains, central tablelands, South West Slopes, Southern Tablelands and Riverina. (For a graphic on Australia's wheat growing regions: link.reuters.com/qev98q and more detailed weather forecasts: www.weatherzone.com.au/) (Additional reporting by Amy Pyett in Sydney; Editing by Ed Davies, Himani Sarkar)