According to Official Guinness Records,
The longest continuous oil-spill burn at sea is 11 hours 48 minutes and was started deliberately by Elastec/American Marine, Inc. (USA)) to remove oil spilled as a result of the explosion on board the Deepwater Horizon oil drilling rig in the Gulf of Mexico, USA. The burn occurred on 19 May 2010.
For a complete list of 2010 records, please visit 2010 Guinness Records in United States.