The Montara oil spill report

摘要

On 21 August 2009, a blowout occurred on the HI well of the Montara Wellhead Platform.1 On the same day, all 69 personnel of the platform were safely evacuated.2 The most likely cause of the blowout was the failure of the primary well control barrier (a cement shoe casing).3 Further, only one of two planned secondary well control barriers (pressure containing anti-corrosion caps) had been installed.4 Following the blowout, oil began to leak into the sea. The rate of discharge was initially estimated at 400 barrels a day, though it may have reached 1500 barrels.5 Estimates of the resulting surface sheen ranged from 6000-25,000 square kilometres.6 The discharge was finally stopped in November 2009, when the well's operator, PTTEP Australasia (Ashmore Cartier) Pty Ltd (PTTEPAA), successfully drilled a relief well (after several failed attempts).7 While impacts on islands in the area and the Western Australian coastline were "largely avoided", because of remoteness and a lack of evidence, the exact nature of the environmental impact will never be known.8