Petty Officer 2nd Class Bill Colclough said the spill was reported to authorities on Tuesday.
Colclough said a sheen created by the spill has dispersed and none of the spilled oil was recoverable.
The site, designated as Grand Isle Block 43, is about 100 miles west of BP's Macondo well.
The BP well spewed more than 200 million gallons of oil after an explosion aboard the rig Deepwater Horizon in April 2010. The BP spill was the nation's largest offshore oil spill.