petroleum was discovered on 3 march 1938 and followed up by several other finds in the eastern province. saudi arabia has since become the world's second largest oil producer (behind the us) and the world's largest oil exporter, controlling the world's second largest oil reserves and the sixth largest gas reserves. the kingdom is categorized as a world bank high-income economy with a high human development index and is the only arab country to be part of the g-20 major economies.