Global technically recoverable oil shale reserves have recently been estimated at about 2.8 to 3.3 trillion barrels (450×10^9 to 520×10^9 m3) of shale oil, with the largest reserves in the United States, which is thought to have 1.5–2.6 trillion barrels (240×10^9–410×10^9 m3).[14][2] [44][45] Worldwide production of shale oil was estimated at 17,700 barrels per day (2,810 m3/d) in 2008. The leading producers were China (7,600 barrels per day (1,210 m3/d)), Estonia (6,300 barrels per day (1,000 m3/d)), and Brazil (3,800 barrels per day (600 m3/d)).[14]