More oil has been found in block 15 operated by Esso off Angola, where Statoil is a partner.
Located about 370 kilometres north-west of the Angolan capital, Luanda, this discovery has been named Dikanza.
Three earlier finds - Kissanje, Marimba and Hungo - have been made in this acreage, and Esso puts total recoverable reserves there at more than a billion barrels of oil equivalent.
The Dikanza discovery well was drilled in 1,154 metres of water. During production testing, the operator reports, it flowed 4,400 barrels per day.
Esso plans to continue appraisal drilling in block 15, where Statoil has a 13.33 per cent interest.
The group has a matching holding in Angolan block 17. Operator Elf is planning to develop the Girassol discovery in the latter acreage.
"Dikanza is an important discovery, which confirms our understanding of the area," says Jon Bakken, who heads Statoil's Angola commitment.
"Although this find does not rank as particularly large in itself, it contributes to a substantial reserve base in these waters."