Possible Bilge Dumping, Offshore Brazil

We’ve been looking at satellite imagery of offshore Brazil regularly since Chevron’s November 2011 blowout and spill in the Campos Basin.  Yesterday Teri noticed what appears to be a 40-mile-long, thin slick about 50 miles offshore in the southern part of the Campos oil field, playing hide-and-seek between the clouds and cloud shadows, on a MODIS/Terra satellite image: 

Given the location, one might suspect this is a leak from one of the many oil platforms or FPSOs in this area, shown as purple dots in the image above.  Petrobras platform Namorado-2 is located close to the north end of this slick. But we think, given it’s length and consistent width, this is more likely a bilge-dumping slick or leak from a passing vessel than a leak from a platform.

Is bilge dumping legal in Brazilian waters?  And who is the culprit? There is plenty of coastal shipping activity in this area, including cargo ships that we’ve caught dumping bilge elsewhere. There is also a lot of tanker traffic here, hauling oil from the FPSOs offshore to storage facilities and refineries onshore, occasionally causing spills here in Brazilian waters.  

If we had to place a bet, we would guess this is bilge dumping from a shuttle tanker serving the Campos Basin oil facilities. Teri is running through the AIS data now to see if she can identify the source of this slick.