An oil spill from a leaking PTT Exploration & Production Pcl field that’s threatening marine life off Australia’s far north-west coast is “appalling,” Prime Minister Kevin Rudd said.  “It’s appalling that this has occurred, but we are working to deal with the situation as it unfolds,” Rudd told a radio station in Perth today, according to an e-mailed transcript. The slick is about 148 kilometers (92 miles) off the coast, he said.

Oil, gas and condensate started seeping into the Timor Sea Aug. 21 from 3,500 meters (11,500 feet) below the ocean floor at the Montara project. PTTEP, Thailand’s only publicly traded oil exploration company, said Aug. 23 it may take 50 days to plug the leak from the well, about 250 kilometers off the coast of the Kimberley wilderness region.

Oil covers about 25 percent of the spill’s range, which is now 70 nautical miles by 25 nautical miles, Rudd said today. PTTEP must be transparent with regulators, including the National Offshore Petroleum Safety Authority, to meet Australian legal and regulatory requirements, he said.

The Kimberley coast is described by Tourism Australia as “one of the world’s last true wilderness areas.” Western Australia accounted for two-thirds of Australia’s oil production last year and 71 percent of the nation’s gas output. Much of that comes from the state’s northwest coast.

The West Triton rig, which will drill a relief well intended to plug the leak, is on schedule to reach the Montara field on Sept. 8, PTTEP said today in a statement. The rig left Indonesia’s Batam Island, near Singapore, on Aug. 28.  PTTEP said yesterday it continues to work with the Australian Maritime Safety Authority, which is managing the response to the spill.