Andrea Hayward WA Today 22 Oct 09;
The amount of oil leaking from a wellhead in the Timor Sea could be more than five times higher than its operators estimate, and is now the third-worst spill in Australian history, environmental groups say.
Oil has been leaking from the Montara wellhead, more than 200km north-west of West Australia’s Kimberley coastline, since August 21.
The Thailand-based company which operates the oilfield, PTTEP Australasia, put the initial rate of flow of oil at the site at 400 barrels a day and says the flow has diminished.
Based on the company’s estimates, the spill could have leaked up to 3.7 million litres of oil since it began.
But the Greens say the actual figure is between 10 and 20 million litres.
Greens Senator Rachel Siewert said officials from the federal resources, energy and tourism departments had revealed the discrepancy during questioning at a Senate estimates hearing on Wednesday.
PTTEP had failed to give the officials any basis for its calculations on the rate of the oil flow, Senator Siewert said.
Based on data from Geoscience Australia the flow could be about 2000 barrels a day, plus condensate, she said.
Based on PTTEP’s own documents and data from similar wellheads nearby, an independent analysis sourced by the Greens calculated the Montara wellhead could be leaking as much as 3000 barrels of oil a day.
"It is clear that we have no confidence in the estimates by the company and I must ask why the government chose to support the company’s estimates rather than the department’s estimates," Senator Siewert said.
"It is a clear that a thorough and comprehensive inquiry is needed into this spill," she said.
"If the oil had continued to leak at this rate over the two months since the accident on August 21, this would suggest that up to 20 million litres of oil could have leaked into the Timor Sea.
"However, given the drop-off in the observed rate of oil leakage in the first weeks of the spill reported by AMSA, we might expect that the total amount of oil spilled could be lower, perhaps around 10 million litres."
The West Triton drilling rig, which reached the site five weeks ago after being towed from Singapore, is being used in attempts to intercept the leaking well, 2.6km under the seabed, and pump in heavy mud to block the leak.
It has to intersect a 25cm-diameter casing, which is detected by sophisticated electro-magnetic ranging tools, before the plugging operation can proceed.
Three failed attempts have been made to plug the leaking well. Another attempt is expected on Friday.
Conservation groups have been critical of the response to the oil spill.
John Carey of Pew Environmental Group, an environmental advocacy organisation, said the spill was now Australia’s third worst oil spill, based on the Geoscience Australia data.
"The oil spill has fluctuated since it began but the revelations overnight indicate that the amount of oil polluting the sea off the Kimberley coast is likely to be almost three times more than what was previously thought," Mr Carey said.
"Halting this spill is the first priority, the second priority is to make sure that there are safeguards put in place to protect the marine environment from future spills and create large sanctuary areas as a safe haven for marine life."
AAP
