answers: Russia
context: global reserves), Saudi Arabia (18% of global reserves), Canada (13% of global reserves), and Iran (9%). Because the geology of the subsurface cannot be examined directly, indirect techniques must be used to estimate the size and recoverability of the resource. While new technologies have increased the accuracy of these techniques, significant uncertainties still remain. In general, most early estimates of the reserves of an oil field are conservative and tend to grow with time. This phenomenon is called "reserves growth". Many oil-producing nations do not reveal their reservoir engineering field data and instead provide unaudited claims for their oil reserves. </s> Natural gas in Qatar The natural gas in Qatar covers a large portion of the world supply of natural gas. According to the "Oil & Gas Journal", as of January 1, 2011, reserves of natural gas in Qatar were measured at approximately ; this measurement means that the state contains 14% of all known natural-gas reserves, as the world's third-largest reserves, behind Russia and Iran. The majority of Qatar's natural gas is located in the massive offshore North Field, which spans an area roughly equivalent to Qatar itself. A part of the world's largest non-associated, natural-gas field, the North Field, </s> stated reserves. In 2000, the US Geological Survey estimated that remaining undiscovered oil reserves in Saudi Arabia had a probability-weighted average of 90 Gbbl. Saudi Arabia has traditionally been regarded as the world’s most important swing producer of oil. When acting as such, the Saudi government would increase or decrease oil production to maintain a more stable price. Saudi Arabia produced (Mbbl/d) in 1980, 10.6 Mbbl/d in 2006, and in the region of 9.2 Mbbl/d in 2008. Saudi Arabia maintains the world’s largest crude oil production capacity, estimated to be approx. 11 Mbbl/d at mid-year 2008 and announced plans to
question: which country is the world 's largest producer of crude oil