The Montara oil spill was an oil and gas leak and subsequent slick that took place in the Montara oil field in the Timor Sea, off the northern coast of Western Australia. It is considered one of Australia's worst oil disasters. The slick was released following a blowout from the Montara wellhead platform on 21 August 2009, and continued leaking until 3 November 2009 (in total 74 days), when the leak was stopped by pumping mud into the well and the wellbore cemented thus "capping" the blowout. The West Atlas rig is owned by the Norwegian-Bermudan Seadrill, and operated by PTTEP Australasia (PTTEPAA), a subsidiary of PTT Exploration and Production (PTTEP) which is in turn a subsidiary of PTT, the Thai state-owned oil and gas company was operating over on adjacent well on the Montara platform. Houston-based Halliburton was involved in cementing the well. The Montara field is located off the Kimberley coast, 250 km (160 mi) north of Truscott airbase, and 690 km (430 mi) west of Darwin. Sixty-nine workers were safely evacuated from the West Atlas jackup drilling rig when the blowout occurred.
The Australian Department of Resources, Energy and Tourism estimated that the Montara oil leak could be as high as 2,000 barrels (320 m3)/day, five times the 400 barrels (64 m3)/day estimated by PTTEP Australasia. A spokesman for Resources Minister, Martin Ferguson, said the of 2,000 barrels (320 m3) referred to the amount of oil that the well could produce when bought into peak production. After flying over the spill site, Australian Greens Senator Rachel Siewert claimed the spill was far greater than had originally been reported. WWF-Australia also claimed that the spill was worse than originally expected.
Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years. Fossil fuels contain high percentages of carbon and include coal, petroleum, and natural gas. They range from volatile materials with low carbon:hydrogen ratios like methane, to liquid petroleum to nonvolatile materials composed of almost pure carbon, like anthracite coal. Methane can be found in hydrocarbon fields, alone, associated with oil, or in the form of methane clathrates. The theory that fossil fuels formed from the fossilized remains of dead plants by exposure to heat and pressure in the Earth's crust over millions of years (see biogenic theory) was first introduced by Georg Agricola in 1556 and later by Mikhail Lomonosov in the 18th century.
The Energy Information Administration estimates that in 2007 the primary sources of energy consisted of petroleum 36.0%, coal 27.4%, natural gas 23.0%, amounting to an 86.4% share for fossil fuels in primary energy consumption in the world. Non-fossil sources in 2006 included hydroelectric 6.3%, nuclear 8.5%, and others (geothermal, solar, tidal, wind, wood, waste) amounting to 0.9%. World energy consumption was growing about 2.3% per year.