Ghawar is an oil fiel in Saudi Arabia. It is located about 100 km WSW from the city of Dhahran in Al-Ahsa county of the Eastern Province. Measuring 280 km by 30 km, it is by far the largest conventional oil field in the world. The field is entirely owned and operated by Saudi Aramco, the nationalized Saudi oil company. Relatively little is known about Ghawar because the company and Saudi government closely guard field performance information and per-field production details. Available information is predominantly historical (pre-nationalization), from incidental technical publications, or anecdotal.