UPDATE 1-Cyclone brews off Australian oil, mining region

* Low pressure system may intensify into cyclone by Sunday

* Oil and gas, mining operators say operating as usual (Adds oil and gas operations, comments from Woodside, Apache)

SYDNEY Jan 15 (Reuters) - Australia's giant Port Hedland iron ore terminal is monitoring a low pressure system threatening to intensify into a cyclone by Sunday but has no immediate plans to activate emergency procedures, a port spokeswoman said on Friday.

BHP Billiton Ltd/Plc (BHP.AX)BHP.L, the port's biggest user, also said it was keeping any eye on the system and was ready to take precautionary steps, if needed.

Cyclones frequently flood roads and railways, disrupting mining and haulage lines.

The possible cyclone could also threaten some of Australia's largest oil and gas projects, among them the onshore North West Shelf liquefied natural gas (LNG) processing plant and several offshore oil production sites that produce a total of about 113,000 barrels of oil per day, accounting for around three-quarter of the country's total production.

Woodside Petroleum Ltd (WPL.AX), operator of the North West Shelf LNG processing plant, and U.S. Apache Corp (APA.N) both said they were monitoring the situation but continued to operate as normal.

The Bureau of Meteorology has warned the system had a more than 50 percent chance of strengthening over the weekend as it made its way north, northwest of the coastal community of Exmouth, near Port Hedland in far west Australia.

Port Hedland handled 14.87 million tonnes of iron ore exports last month, most mined by BHP Billiton, Fortescue Metals Group, FGM.AX and Atlas Mining (AGO.AX)

Port Hedland typically shuts down and orders berthed ships to safe harbours if a cyclone in the region is deemed likely. Most storms pass within a few days.

The cyclone would be the second major storm of the November-to-April season to form in Australia's "cyclone alley" after Cyclone Laurence shut mines and ports in December.

There are normally about five cyclones each season.