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, north of Truscott airbase, and west of Darwin. Sixty-nine workers were safely evacuated from the West Atlas jackup drilling rig when the blowout occurred.(21 August 2009). . PTTEP Australasia. Retrieved 18 March 2012.
The Australian Department of Resources, Energy and Tourism estimated that the Montara oil leak could be as high as /day, five times the /day estimated by PTTEP Australasia. A spokesman for Resources Minister, Martin Ferguson, said the 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 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.Peter Ker (29 September 2010). Plan to tow oil rig to Singapore. The Age. Fairfax Media. Retrieved 18 March 2012.
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 and depth of hole was approximately 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 long and wide. On 29 August, the slick was estimated at at a minimum, measured east to west.
By 3 September 2009, the Australian Maritime Safety Authority (AMSA) reported that the slick was from the coast of Western Australia, and moving closer to the shore. The slick was also reported to have spread over of ocean with evidence that the oil was killing marine life. Reports that the slick had spread to within 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.Michael Bennett (10 August 2010). Montara oil spill 'did not reach Kimberley. The West Australian. Retrieved 18 March 2012. 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.K.W. McAlpine, C.B. Sim, R.J. Masini and T. Daly. Baseline petroleum hydrocarbon content of marine water, shoreline sediment and intertidal biota at selected sites in the Kimberley bioregion, Western Australia . Office of the Environmental Protection Authority. July 2010. Retrieved 18 March 2012.
Clean-up and response The Australian Marine Oil Spill Centre began mobilising aircraft and equipment on 21 August 2009. On 23 August 2009, a Hercules aircraft sprayed 10,000 liters of chemical dispersant onto parts of the slick, with ongoing aerial spraying with dispersants being the primary early response to the spill. Spraying from vessels commenced on 30 August and continued until 1 November utilising 118,000 liters of dispersant. Six different chemical dispersants were used: Slickgone NS, Slickgone LTSW, Ardrox 6120, Tergo R40, Corexit 9500 and Corexit 9527. In total, 184,135 liters of chemical dispersants were sprayed from aircraft or vessels between 23 August and 1 November.
The West Triton jackup drilling rig arrived at the Montara Field in an attempt to plug the oil leak on 11 September 2009."Finally, help arrives at stricken West Atlas oil rig", The Sunday Times. Oil and gas producer, Woodside Petroleum Ltd offered to assist PTTEPAA in cleaning up the oil spill with the use of a rig closer to the spill site. However, PTTEPAA rejected the Woodside offer on the basis of "safety reasons". The Woodside rig was a semisubmersible drilling rig and, as it floats on the sea surface, was not deemed as a suitable platform for the relief well. A jackup rig was required because it could be secured to the sea floor giving better stability and had the capacity to pump large volumes of heavy mud needed to stop the leak. On 6 September, the plugging of the oil leak was delayed further by a broken towline to the mobile oil rig being towed in from Indonesia by PTTEPAA. On 7 September, the Australian Federal Government announced that it was suspending the normal approval process to fast track stopping the leak at the West Atlas oil rig. PTTEP Australasia initially said it could be just days before the leak was brought under control, but then said that the oil leak would continue for eight weeks until they could bring in another mobile offshore rig, West Triton, to drill a hole into the leaking oil well, and pump mud in to alleviate pressure to stop the oil flow.
On 1 November 2009, the West Triton rig successfully drilled the relief well to intercept the leaking well. During operations to kill the leak by pumping heavy mud down the relief well, a fire broke out from the H1 well on the well head platform. This was expected to delay further work on resolving the spill. All eight non-essential personnel were taken off the West Triton rig.
On 1 November 2009, the fifth attempt to intercept the well succeeded. Approximately of heavy mud were subsequently pumped down the relief well on 3 November 2009 thereby stopping the leak and extinguishing the fire. PTTEPAA continued to pump a mixture of heavy mud and brine into the relief to maintain a stable condition before it was eventually cemented. Once the leak was killed, the main fire on the Montara Wellhead platform was extinguished. Some material on the topside of the West Atlas rig remained on fire but had extinguished by 3 November 2009 as the fuel source burnt out.
In July 2010, a PTTEPAA team rebounded the well head platform to pressure test all the wells. Following a three-week operation, the company confirmed all wells were secure.
PTTEPAA estimates that it has spent $170 million on the gas and oil leak up to 3 November 2009. The environmental clean-up cost $5.3 million. Since the spill originated directly from an oil well, it is difficult to determine its total size with any precision. Estimates range from to more than , or about 4,000 tonnes to 30,000 tonnes.
Environmental effects The Australian Government in November 2010 released the first results of an independent scientific studies conducted under the long-term environmental monitoring program being funded by PTTEPAA under an agreement with the Australian Government announced in October 2009. The scientific studies issued by the Australian Department of Sustainability, Environment, Water, Population and Communities (DSEWPaC) on 19 November 2010 found that no oil reached the Australian mainland or Indonesian coast and the maximum surface area of the ocean that had hydrocarbons on it on any one given day during the spill was 11,183 square kilometres. The Australian Government sought independent expert advice on the detail of the environmental monitoring program from organizations such as the Australian Institute of Marine Science, the Commonwealth Scientific and Industrial Research Organization (CSIRO) and State and Territory agencies. Each scientific study conducted under the program is subject to a detailed review by a DSEWPaC technical advisory board. PTTEPAA will fund the comprehensive monitoring program for at least two years, with some studies expected to continue up to five years or longer if required to provide data to measure and address any longer-term impacts should they occur. A PTTEPAA spokesperson said "the commitment to run some of the studies beyond two years does not necessarily indicate long-term impacts but supports the recommendations of independent experts to ensure the best science is in place to monitor the marine environment".