Apache Corp. said it encountered around 250 net feet of oil pay at block 903 in the Green Canyon reserve in roughly 5,000 feet of water off the southern U.S. coast.
The well was drilled to a depth of 31,000 feet about 1.5 miles south from Apache's Heidelberg discovery well.
"Log and pressure data from the appraisal and discovery wells indicate excellent quality, continuous and pressure-connected reservoirs with the same high-quality oil," the company said in a statement.
Oil companies returned to work in the Gulf of Mexico after the U.S. government lifted a ban on deep-water work imposed in response to BP's oil spill in 2010. The government has since opened up parts of the oil-rich region to new developments.
In October, the U.S. Bureau of Ocean Energy Management said it approved of BP's supplemental exploration plan following a site-specific environmental assessment.