The latest discovery off Ivory Coast's eastern shore "increases by about 25 percent" the previously announced deposits, the ministry for mines, oil and energy said in a statement, with extraction due to start in early 2023.
In September 2021, the country had announced a find of deposits estimated at between 1.5 and 2 billion barrels of oil and around 51-68 million cubic meters of gas.
International companies including French giant Total and Britain's Tullow Oil have also announced significant discoveries of Ivorian offshore oil reserves in recent years.
President Alassane Ouattara has said he wants Ivory Coast to become a major oil producer. The West African nation's current output is modest, at around 30,000 barrels per day.