The Department of Transport says the oil spillage off the south coast is now around 55km (30 nautical miles) from land.
Watch the latest aerial footage of the oil slick
The slick contains more than 520 tonnes of fuel oil, and is at least 6km long and wide.
It is said to be breaking up and reducing naturally and spreading over a large area - it is not yet known when the slick will reach Irish shores.
Yesterday, the Coast Guard said the slick could land on the Wexford coast within 16 days.
There is currently an easterly wind in the area off the Old Head of Kinsale.
Aerial surveillance on Saturday confirmed the spill surrounding a Russian aircraft carrier and a refuelling tanker.
The Russian Navy has admitted that two of its vessels refuelled near the site of the incident, but denied it was responsible.
A spokesman said there had not been an accident on board, or deliberate dumping of fuel overboard.
Igor Dygalo disputed the size of the oil spill, saying it neither 'has a catastrophic character nor constitutes a threat to coastal ecology'.
