Safaniya Oil Field, operated and owned by Saudi Aramco, is the largest offshore oil field in the world. It is located about 265 kilometres (165 mi) north of the company headquarters in Dhahran on the coast of the Persian Gulf, Saudi Arabia. Measuring 50 by 15 kilometres (31.1 by 9.3 mi), the field has a producing capability of more than 1.2 million barrels per day (190×103 m3/d).

The oil field was discovered in 1951. It is considered the largest offshore oil field in the world. When it was first put in production in 1957, it flowed 50,000 barrels per day (7,900 m3/d) of crude oil from 18 wells. 

At the beginning of 1962 it possessed the facilities to handle 350,000 barrels per day (56,000 m3/d) from 25 wells. This sevenfold increase evolved in just four years and nine months. Its reserve amount to around 37 billion barrels (5.9×109 m3) of oil and 5,360 billion cubic feet (152×109 m3) of natural gas.

The main producing reservoir is the Safaniya which is a cretaceous sandstone in the Wasia formation. Most geologist believe that the Safaniya field and the neutral Zone Khafji field share the same aquifer that continues toward Kuwait's Burgan field. 

The Safaniya field has several separate geologic production potential at depths between 4,000 and 7,000 feet. It was brought into production in 1957 at about 25,000 barrels per day. By 1993, there were a total of 624 wells in the field.

According to en.wikipedia