AIM-listed Sirius Petroleum has discovered that its Ororo field offshore Nigeria is larger than first expected.An independent evaluation conducted by Schlumberger on the shallow-water Ororo Field confirmed estimated hydrocarbons in place of between 35.2-44.1 million stock tank barrels of oil (MMSTB).Recoverable oil from the single Ororo-1 well, where seven oil bearing sands were identified, was estimated at 10-12.8 MMSTB and which flow tested at a combined production rate of approximately 2,800 barrels of oil per day.Chief Executive Bobo Kuti, who was promoted from Business Development Director in September, said: "The independent assessment of the oil in place in the first of our portfolio of assets to be exploited, the Ororo field, indicates a greater asset base than we had originally expected. "Sirius is now in discussions with Schlumberger to provide project management and drilling services to accelerate the long-awaited development of this asset and take it to first-oil, which Kuti said was "a major first step for the company".Shares in Sirius were up 13.8% to 4.13p at 10:00 on Tuesday.OH