A production test from a field located offshore Congo has exceeded company expectations, the top executive at Italian energy company Eni said Monday.

Eni said it completed a production test in the Minsala Marine 1 NFW well off the Congolese coast, yielding more than 5,000 barrels of oil and 14 million cubic feet of natural gas per day in natural flow.

"The production test results has exceeded expectations and enables us to plan a fast commercial development of the important Minsala Marine find," Eni Chief Executive Officer Claudio Descalzi said in a statement.

The company said it estimates the discovery holds about 1 billion barrels of oil equivalent in place, of which 80 percent is oil.

Reserves off the West African coast are similar to those in Brazil in that they're located beneath a thick layer of submarine salt. Eni said it's already discovered about 4 billion barrels of oil in basins off the Congolese and Gabonese coasts since it started work there more than four years ago.

Eni has been operating in Congo since the late 1960s, producing around 100,000 barrels of oil per day.