Oil reserves in Saudi Arabia: The proven oil reserves in Saudi Arabia are reportedly the second largest in the world, estimated in 2017 to be 268 billion barrels (4.3×10^10 m3) (Gbbl hereafter), including 2.5 Gbbl in the Saudi–Kuwaiti neutral zone. This would correspond to more than 50 years of production at current rates. In the oil industry, an oil barrel is defined as 42 US gallons, which is about 159 litres,[1] or 35 imperial gallons.[2] The oil reserves are predominantly found in the Eastern Province.[3] These reserves were apparently the largest in the world until Venezuela announced they had increased their proven reserves to 297 Gbbl in January 2011.[4] The Saudi reserves are about one-fifth of the world's total conventional oil reserves. A large fraction of these reserves comes from a small number of very large oil fields, and past production amounts to 40% of the stated reserves. Other sources state that Saudi Arabia has about 297.7 billion barrels.[5] In 2000, the US Geological Survey estimated that remaining undiscovered oil reserves in Saudi Arabia had a probability-weighted average of 90 Gbbl.[6]