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 75 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 2,000 barrels (320 m3) referred to the amount of oil that the well could produce when brought 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. The first four attempts to plug the oil leak by PTTEPAA failed, but the fifth attempt succeeded on 3 November 2009, when PTTEPAA pumped approximately 3,400 barrels (540 m3) of mud into a relief well to stop the leak. On 1 November 2009, during an attempt to stop the leak, a fire broke out on the West Atlas drilling rig. On 2 November, PTTEPAA said that the fire appeared to be burning off the oil and thereby preventing further leakage into the sea. The fire was largely extinguished when the leak was stopped. Once safety criteria were met, a specialist team boarded the Montara wellhead platform and the West Atlas to assess the damages. The operation later in November 2009 to finally plug the well after the leak was stopped involved pumping a 1,400 metre cement plug from the West Triton rig down the relief well to the bottom of the 2.5 kilometre well. Once completed, the West Triton relief rig was demobilized and returned to Singapore. In December 2009, a team from PTTEPAA and Alert Well Control returned to the Montara field to complete the final stages of the operation, which involved inserting two mechanical barriers at depth above the cement plug into the well. Operations were completed in January 2010 when the reboarding team installed a capping assembly on the well. Work to safely remove the West Atlas drilling rig from the Montara well head platform (WHP) in the Timor Sea started in August 2010. The offshore construction vessel Jascon 25 equipped with an 800-tonne crane was mobilized for the salvage operations. This work was expected to take about three months and involve cleaning and removal of debris from the rig as well as the cantilever drill floor which was left extended over the WHP helideck after the fire in November 2009. After the debris removal work was completed, this was followed by the jacking down of the West Atlas rig to be towed to Singapore. PTTEPAA announced a major transformation of its Australian drilling operations on 24 November 2010 following the release of the Australian Government's Montara Commission of Inquiry report into causes of the incident. The company said it was implementing a nine-point Action Plan to embed the highest standards of oil field practice and safety in its operations. PTTEPAA said it regretted the Montara incident and acknowledged there were deficiencies identified in the company's operations in the Commission of Inquiry's report. The company said drilling supervisors and management associated with the incident have been removed from their positions with the company. According to a company spokesman, the Action Plan will "ensure the full accountability of key personnel to give greater oversight for reporting and checking of all critical offshore operations. This will strengthen the integrity and safety of drilling operations".
Initial leak and spread
The leak initially emanated from the Montara Wellhead platform on 21 August 2009. The depth of water was approximately 250 ft (76 m) and depth of hole was approximately 1.6 mi (3 km) below the seabed. Sixty-nine workers on the rig were safely evacuated with no injuries or fatalities. By 24 August, the oil slick resulting from the spill was estimated to be 14 km (9 mi) long and 30 m (100 ft) wide. On 29 August, the slick was estimated at 180 km (110 mi) at a minimum, measured east to west. By 3 September 2009, the Australian Maritime Safety Authority (AMSA) reported that the slick was 170 km (106 mi) from the coast of Western Australia, and moving closer to the shore. The slick was also reported to have spread over 6,000 km2 (2,300 sq mi) of ocean with evidence that the oil was killing marine life. Reports that the slick had spread to within 120 km (75 mi) of the Northern Territory coastline were dismissed as incorrect, with the AMSA stating that the discoloured water was likely to be a natural phenomenon, such as an algal bloom or coral spawn. Daily overflights by the Australian authorities in September and October 2009 identified isolated patches of weathered oil and sheen within Indonesian waters with small patches seen 94 kilometres south east of Roti Island. At the time the main spill was located about 248 kilometres from the Indonesian coastline. The West Australian newspaper online reported that no oil had reached the Kimberley coastline in northern Western Australia. The report was based on a West Australian Environmental Protection Authority study conducted in October 2009 during the spill. The study, released in July 2010 stated no traces of hydrocarbons were found in water or shoreline sediments in areas sampled between Camden Sound and the Stewart Islands.
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