Abstract

The Phanerozoic succession of Saudi Arabia holds the world’s largest liquid hydrocarbon reserves, and the world’s fourth largest gas reserves. This sedimentary succession was deposited on the southwestern margin of the Tethys Ocean, where favorable conditions existed for the optimal juxtaposition of multiple source, reservoir, and seal rocks and the creation of large structural traps. Two major petroleum systems occur in eastern and central Saudi Arabia: a mixed siliciclastic/carbonate Paleozoic petroleum system associated with Proto-Tethyan and Paleo-Tethyan settings, and a carbonate-dominated Mesozoic petroleum system associated with the Neo-Tethys.

The Paleozoic petroleum system hosts one carbonate and eight siliciclastic oil and gas reservoirs, and at least one source rock, the Qusaiba Formation of Early Silurian age. The Jurassic portion of the Mesozoic petroleum system hosts at least 14 carbonate reservoirs and at least three source rocks, of which intrashelf basin-derived organic-rich fine grained carbonates of the Middle Jurassic Tuwaiq Mountain and Upper Jurassic Hanifa Formation are the most significant. The Cretaceous portion of the Mesozoic petroleum system includes nine carbonate reservoirs, four clastic reservoirs, and several source intervals.

Hydrocarbon traps predominately comprise large, low relief anticlines formed by contractional folding in the sedimentary cover above deep-seated basement faults. Examples include the Ghawar structure which hosts the world’s largest oil field with reservoirs ranging in age from Permian through Jurassic, and Safaniya and adjacent fields which form the world’s largest offshore oil field complex within Lower Cretaceous reservoirs. In addition, halokinesis occurs locally and is a component of the trapping mechanism for several individual fields in eastern Saudi Arabia.