How big is the Montara oil leak off the northern coast of Western Australia?

Tiny, says the company responsible, Thailand energy giant PTTEP. Large but heading away from the coast, says the Australian Maritime Safety Authority. Huge and dangerously close to the Kimberley coastline, say the Greens.

The leak might have dropped out of the media cycle but it continues to discharge oil into an area 25 nautical miles by 70 nautical miles about 180 kilometres off the Western Australian coast, according to Australian Maritime Safety Authority data.

There has been no advice from either PTTEP or AMSA about the rate of discharge. The Greens used similar wells in the region to estimate that 3000 barrels of oil a day were being released. In the seven weeks it is expected to take to bring a mobile offshore drilling rig to the site and drill a relief well to stop the leak, that means just over half-a-billion litres of oil will be discharged. According to PTTEP’s own data, the area features 12 endangered or vulnerable species under the Environmental Protection and Biodiversity Conservation Act, including the blue whale.

PTTEP last week said the resulting oil slick was eight nautical miles long and 30 metres wide (about 14 sq kilometres) “and showing no signs of expanding.” On Saturday, AMSA, which is in charge of cleaning up the leak, said its over-flights showed it was much larger: “the slick covers a rectangular area approximately 15 nautical miles to the north of the Montara Well head platform and 60 nautical miles to the east of the rig. Only 25% of this area is affected by the leak, consisting of streaks of oil and patches of sheen. The heavier concentrations of oil surround the rig out to a distance of 3 nautical miles.”

After flying over the spill on Friday, Greens Senator Rachel Siewert said the leak was 180 kilometres in length and had reached 20 kilometres from the coast. AMSA seemed at pains to contradict her indirectly in an update on Saturday, in which AMSA said the slick was “in excess of 80 nautical miles” from the coast:

AMSA conducts training courses in aerial observations for its own staff as well as other agencies that are involved in this type of work. It is notoriously difficult to distinguish between oil and a variety of other unrelated phenomena such as: cloud shadows, ripples on the sea surface, differences in the colour of two adjacent water masses, suspended sediment, floating or suspended organic matter, floating seaweed, algal/plankton blooms.

It seemed an unsubtle suggestion that Senator Siewert didn’t know what she was talking about. AMSA’s Mick Spinks denied that, however. “That wasn’t intended to counter any views anyone has put,” he told us this morning. He did point out, however, that AMSA used over-flights, data from buoys deployed in the slick to monitor wind and surface drift and satellite photos, such as this one taken yesterday, to track the slick.

The slick from space

“The slick has spread north-east from the well-head, with heavy clustering in that area around the rig. It’s 100 nautical miles from the coast.” It would take, Spinks said, an “act of God” for the wind and tidal patterns to change sufficiently for the slick to head toward the coast.

With the leak continuing for several weeks, AMSA has relied on oil dispersants delivered from aircraft to break up the slick. The actual dispersant being used has not been publicly revealed, although AMSA has an extensive FAQ on what they do and what problems they can cause, which are significantly greater in shallower waters, which is why the proximity to the coast is such an important issue. According to the Australian Institute of Marine Science, natural oil and gas seeps in the region are fairly common and there is evidence of naturally occurring oil-degrading microbes.

Meanwhile, more evidence is emerging of the background of PTTEP. Perth journalist Tony Serve uncovered close links between PTTEP and the junta in Burma, where PTTEP has four major oil and gas projects either at exploration stage or in production, some in co-operation with Chinese giant CNOOC. Access to, and exploitation of, Burma’s extensive oil and gas reserves is a critical part of Thailand’s energy strategy. PTTEP is also developing a major gas venture in Iran, which has been significantly slowed by Security Council sanctions against the Iranian regime.