Montara oil spill

Montara oil spill
Satellite image of the oil slick in the Timor Sea, September 2009.
Location	Timor Sea, off the northern coast of Western Australia
Date	21 August 2009 to 3 November 2009 (75 days)
Cause
Cause	Leak from the Montara wellhead platform
Operator	PTT Public Company Limited
Spill characteristics
Volume	1.2 to 9 million US gallons (4,500 to 34,100 m3) total
Area	6,000 km2 (2,300 sq mi)

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.^[1] 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.^[2][3] 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.^[4] 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.^[5][6][7] Sixty-nine workers were safely evacuated from the West Atlas jackup drilling rig when the blowout occurred.^[6][8]

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.^[9] 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.^[10] After flying over the spill site, Australian Greens Senator Rachel Siewert claimed the spill was far greater than had originally been reported.^[11] WWF-Australia also claimed that the spill was worse than originally expected.^[12][13]

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.^[2][3][14]

On 1 November 2009, during an attempt to stop the leak, a fire broke out on the West Atlas drilling rig.^[15] On 2 November, PTTEPAA said that the fire appeared to be burning off the oil and thereby preventing further leakage into the sea.^[16] The fire was largely extinguished when the leak was stopped.^[2][17] 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.^[18]

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.^[19]

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.^[20] After the debris removal work was completed, this was followed by the jacking down of the West Atlas rig to be towed to Singapore.^[21]

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".^[22]