The find occurred at a well drilled on the Stabroek Block - a 6.6 million acre-spanning joint venture licence held by Exxon (45%), Hess (30%) and China's CNOOC (25%) about 120 miles off the Guyana coast.
Exxon said the discovery well was spudded on March 5 and drilled to about 5433m in 1743m of water.
"I am encouraged by the results of the first well on the Stabroek Block," ExxonMobil Exploration Company president Stephen Greenlee said.
"Over the coming months we will work to determine the commercial viability of the discovered resource, as well as evaluate other resource potential on the block."
