Exxon becomes the operator in the Tugula South exploration region off eastern South Africa in an agreement with Impact Africa Ltd. The region covers 2.8 million acres off in an area extending from the coastline to waters as deep as 6,500 feet.
Future exploration rights, the company said, may include another 16 million acres in water depths as deep as 9,800 feet.
Stephen Greenlee, president of Exxon's exploration company, said the deal marked a frontier development for his company.
"We believe South Africa has significant potential and we will continue to look for additional opportunities there," he said in a statement.
Separately, Exxon said it signed a technical cooperation deal with the South African government to examine the hydrocarbon potential in the deep waters of the Durban basin, which covers about 12.4 million acres.
The company didn't indicate its reserve expectations. The U.S. Energy Department's Energy Information Administration estimates South Africa has proven oil reserves of about 15 million barrels but declining natural gas reserves.