The ExxonMobil-controlled Stabroek Block offshore Guyana has now been confirmed to have in excess of four billion oil-equivalent barrels.ExxonMobil announced on Monday that it has increased its estimate of the discovered recoverable resource from a previous estimate of 3.2 billion oil-equivalent barrels and has advanced its evaluation to support a third phase of development and consideration of two additional phases.In a statement, the oil giant said that the increase followed the completion of testing at the Liza-5 appraisal well; a discovery at Ranger; the eighth discovery, Longtail into the Turbot area evaluation; and completion of the Pacora discovery evaluation.According to Exxon, “Guyana’s first development, Liza Phase 1, will use a Floating Production, Storage and Offloading (FPSO) vessel to produce 120,000 barrels of oil per day, starting by early 2020. Liza Phase 2, which is targeted for sanctioning by the end of this year, will use an FPSO vessel designed to produce up to 220,000 barrels of oil per day and is expected to be produced by mid-2022.”According to ExxonMobil Senior Vice President Neil Chapman, continued success in Guyana and progress in other upstream growth projects in the US Permian Basin, Mozambique, Papua New Guinea and Brazil are giving “us additional confidence in achieving our long-term earnings growth plans that we outlined in March”.In addition, it was outlined that the Liza-5 well successfully tested the northern portion of the Liza field and, along with the giant Payara field, will support the third phase of development in Guyana. “The Payara development will target sanctioning in 2019 and will use an FPSO vessel designed to produce approximately 180,000 barrels of oil per day, as early as 2023.”The Longtail well established the Turbot-Longtail area as a potential development hub for recovery of more than 500 million oil-equivalent barrels. Additional prospects to be drilled in this area could increase this estimate.“The collective discoveries on the Stabroek Block to date have established the potential for up to five FPSOs producing over 750,000 barrels per day by 2025. There is potential for additional production from significant undrilled targets and plans for rapid exploration and appraisal drilling, including at the Ranger discovery,” Exxon said.The Stabroek Block covers 6.6 million acres (26,800 square kilometres). ExxonMobil affiliate, Esso Exploration and Production Guyana Limited, is the operator and holds a 45 per cent interest in the Stabroek Block. Hess Guyana Exploration Ltd holds a 30 per cent stake and CNOOC Nexen Petroleum Guyana Limited holds the other 25 per cent.