We’ve just processed an Envisat ASAR radar image of the Campos Basin that was taken on November 25.  As expected, it shows a much smaller apparent oil slick originating from the location of the SEDCO 706 drilling rig, operated for Chevron by Transocean, than we observed back on November 12:

Envisat ASAR satellite radar image taken November 25, 2011. Slicks are dark streaks and patches. Location of SEDCO 706 drill rig is marked. Image courtesy European Space Agency.

Surface wind speed over the leak site was good, about 5-15 knots (3-8 meters/sec), blowing from the north-northeast.  A very narrow slick about 120 meters wide and 50 kilometers long extends south from the rig location, covering about 6 square kilometers.  Assuming the slick is 1 micron thick, we estimate it holds about 1,584 gallons (38 barrels) of oil.

There are other small slicks in the area to the west and southwest of the Chevron leak site.  Some of these may be from natural oil seeps in the basin, other sources of natural surfactant such as phytoplankton, or leaks and spills from vessels and other offshore facilities.