The Ghawar oil field in Saudi Arabia (2) 

According to the most accepted hypothesis, oil in the Ghawar oil field, which produces 5 to 6 million barrels per day, comes from Jurassic calcareous siltstones, which were deposited in inner shield bassins.
 It is important to note that given the immense and sustained production volumes (for more than 70 years)  we should begin to consider their origin from deeper, non-biogenic levels.
The upper seal of the deposit is constituted by anhydrites and it is favored by the general absence of faults in the Jurassic section.
In short, if the biogenic origin is accepted, there would be a rock Jurassic oil source (Hanifa formation) covered by the powerful and porous Arab-D reservoir and an upper anhydritic seal. That is, a great structure with an appropriate thermal and dynamic history.
The abundant production of the deposit was favored through of the injection of water that was started in 1965. The volumes of seawater injected have reached 7 million barrels per day. Apparently, this gas would come from siluric shales (if the biogenic origin is accepted). We should also begin to take into account the possibility of a deeper non-biogenic origin.
The Khuff Perm calcareous reservoirs are the main gas producing areas at depths of 3,000 to 4,000 meters.
In short, it is a sedimentary sequence of several thousand meters with excellent storage conditions for hydrocarbons and a geological source that has supplied huge volumes of liquid hydrocarbons and natural gas from deeper levels. It is assumed that these levels are sedimentary and organic, but should not be excluded, following the theory of Thomas Gold, given the huge amount of accumulated hydrocarbons and their sustained production for a long time, that they may come from a much deeper non-biological origin.