The largest conventional oil field in the world, in Saudi Arabia's Eastern Province, is the Ghawar Field.
Ghawar extends for roughly 280 kilometers from north to south and began producing in 1951. It is operated by Saudi Aramco and has been one of the most important sources of Saudi crude oil for decades. The field lies in a broad geological structure that allowed petroleum to accumulate in porous reservoir rocks beneath impermeable layers.
Ghawar's importance comes from both its enormous size and its production history. It has supplied a substantial share of Saudi Arabia's output, although estimates of its remaining reserves and current production vary. Public reserve figures are not always independently verifiable, so claims about exact depletion dates should be treated cautiously.
Ghawar is different from the world's largest oil-producing region or country. It is a single field, whereas national production totals combine many fields and can change with policy, investment, and market conditions.