SAN JUAN, Puerto Rico—ExxonMobil said Wednesday that it made two additional oil discoveries off the coast of Guyana as the South American country prepares to become the world’s newest major oil producer. The discoveries occurred in an area where officials believe they can extract at least 10 billion oil-equivalent barrels. The company said a vessel that arrived in Guyana late last year is expected to start production in the upcoming months with a target of up to 220,000 barrels of oil a day. Officials said another vessel will start production in 2024. Guyana issued its first oil and gas license to ExxonMobil in 2017 after the company said it made “significant” oil discoveries off the country’s Atlantic coast. The deal is expected to generate up to $5 billion a year for Guyana. ExxonMobil began exploring for oil and gas near Guyana in 2008 and drilled its first exploration well in …