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The West Atlas Oil Spill
The massive fire that engulfed the West Atlas rig last week after workers tried to plug an oil leak. Photo: supplied
Reliance on a whiteboard and a lack of expert oversight contributed to the blowout of a well in the Timor Sea that caused Australia's worst offshore oil spill, an inquiry has heard.
An oil drilling expert told the Montara Commission of Inquiry in Canberra today that a key pressure containing cap was not installed before the blowout at PTTEP Australasia's Montara oilfield.
PTTEP's H1 well, off the north coast of WA, started leaking oil on August 21 last year before it was plugged on November 1 with heavy mud.
The West Atlas oil rig caught on fire and burned at temperatures of 350 degrees celsius for two days before the well was plugged.
David Gouldin, Asia-Pacific operations manager for Seadrill Limited - the drilling contractors on the West Atlas rig - helped prepare a report on the blowout and gave evidence to the inquiry, headed by former public servant David Borthwick.
Under questioning by counsel assisting the inquiry Tom Howe QC, Mr Gouldin agreed that at the time of the blowout, the H1 well did not have any properly tested mechanical barrier in place for six months leading up to the blowout.
He agreed that a pressure cap on the well had not been tested and a bigger pressure cap was not installed as it should have been under the drilling plan.
Mr Howe told the court that a whiteboard in the drilling supervisor's office had the installation of the larger cap as an "outstanding job" but the supervisor said he had no recollection of whether the job had been ticked off as completed.
Mr Gouldin agreed that a whiteboard was an inadequate system to ensure verification of jobs done.
Failure to install the bigger cap led to corrosion of casing threads down the well, which in turn led to the removal of the smaller cap, leaving the well vulnerable to blowout, the court heard.
Mr Gouldin agreed that a defective cemented casing "shoe" was the only mechanical preventer left in the well after the drilling deck moved across to work on another well.
He said the movement of the drilling installation meant the chance of rapid intervention was lost in event of a blowout.
"How does that situation, in your view, conform to good oilfield practice?" Mr Howe asked.
"It doesn't," Mr Gouldin replied.
He said if he had been there, he would not have taken the smaller pressure cap off the well.
"But that's not a company position, that's my personal position," he said.
If the smaller cap had been reinstalled, it was likely it would have prevented the blowout by containing pressure in the wellbore, he said.
Mr Gouldin also agreed that proper supervision of barrier installations should involve someone with sufficient expertise to recognise problems but that was not the case on the Atlas rig.
The inquiry will hear from Seadrill and PTTEP staff and Northern Territory Department of Resources officers during two weeks of hearings.
AAP
