The largest oil field in the world

The Ghawar field in Saudi Arabia is the biggest oil field in the world.
It was discovered in 1937 and is located about 100 kilometers from the city of Dhahran, in the Eastern Province of that country.
It occupies an area of ​​8,400 square kilometers (280 kilometers long by 30 wide).
Currently this site is capable of producing between 4.5 and 5 million barrels of oil a day, which represents the 6% of world production and 65% of Saudi production. It also produces about 2 billion cubic feet of natural gas a day,
Since its production began in 1951 they have been extracted around 60,000 million barrels.
According to oil company Saudi Aramco, owner of Ghawar, still is the largest oil field in the world.
Although its production level has reduced between 2% and 8% every year, there is still a recoverable reserve of some 70,000 million barrels. We must also remember that for three months its production was significantly affected due to the attacks on fields and refineries as a result of the Saudi war against the Yemeni government. 
Geology
The Ghawar oilfield consists of a anticline structure (convex fold)  expressed in the surface by outcrop of tertiary rocks (relatively more modern).
To the north, this structure comprises two anticlines (convex folds) parallel with a small depression among them. The Ghawar anticline rests on a horst (raised block) of the crystalline basement that initially ascended during the carboniferous period (300 million years) and it was reactivated, episodically, especially during the Late Cretaceous (100 million years). The Paleozoic section (ancient, at the base) was significantly eroded by the
Hercinian discordance (that is when the erosion took place) about 280 to 250 million years).
The structure is asymmetric, steeper to the west and is becomes more complex in depth, where there are several horst (raised blocks) in the form of stairs.
The main reservoir of Ghawar is the Jurassic limestones (160-180 million years) that have a somewhat smaller thickness at 100 meters and are located at 2,000-2,300 meters below the surface.
Deposition of limestone rocks included reefs (marine) grainy in the north, improving the quality of the reservoir, which also improves upwards as it evolves from a limestone limestone relatively massive to an oolitic limestone grainy skeletal (oolites are spherical micro-concretions). Fracture density increases with depth increasing the permeability of the fine-grained limolites,
According to the most accepted hypothesis, oil comes from of Jurassic limestone limolites, which were deposited in basins shield interiors It is important to note that given the immense and sustained production volumes should begin to consider its provenance from deeper, non-biogenic levels.
The upper seal of the deposit consists of anhydrides and is favored by the general absence of failures in the Jurassic section 
In summary, if the biogenic origin is accepted, there would be a Jurassic source  rock (Hanifa formation) covered by the powerful and porous Arab-D reservoir and an anhydritic upper seal, which is a  large structure with an appropriate thermal and dynamic history.
The abundant production of the deposit was favored through of the water injection that was started in 1965.
Injected seawater volumes have reached 7 millions of barrils per day
Apparently this gas would come from Siluric shales (if we accept the biogenic origin). We should also start considering the possibility of a deeper non-biogenic origin.
The Khuff Permian Calcareous Reservoirs are the main gas producing areas at depths of 3,000 to 4,000 meters.
It is definitely a sedimentary sequence of several million of years with excellent storage conditions of hydrocarbons and a geological source that has supplied huge volumes of liquid hydrocarbons and natural gas from deeper levels
These levels are supposed to be sedimentary and organic, but it should not be excluded by any means (following the theory of Thomas Gold and several Russian and Ukranian geologists), given the huge amount of accumulated hydrocarbons  and its sustained production for a long time, that they may be of a much deeper non-biological origin.
From the book: "Geography and Geopolitics of Petroleum and Natural Gas"
Danilo Anton, Piriguazú Ediciones