Exploratory drilling in central Saudi Arabia has established significant Paleozoic petroleum potential in this region. In recent discoveries, the Permian interval of the Unayzah Formation has been identified as the primary oil and gas reservoir. The Unayzah Formation consists of alluvial and fluvial to shallow marine siliciclastic sandstones and siltstones that were deposited on a major pre-Unayzah unconformity. Saudi Arabian Paleozoic oil is a high-gravity (43-53 degrees API) crude with low sulfur content (usually less than 0.07%) that is classified as Arabian Super Light oil. Gas with condensate has also been discovered in the Unayzah Formation.

The identified Paleozoic traps are moderate-relief, fault-generated structures, with generally 30-100 m of closure. Unayzah structural traps developed primarily during the Triassic to Early Jurassic; however, an earlier phase of significant pre-Unayzah structural development is also indicated between the Devonian and Late Carboniferous, and is related to a "Hercynian" structural event. Post-Triassic structure in central Arabia is mainly regional and results principally from Late Cretaceous to Tertiary development of the Central Arabian arch.

The established source rock is the basal Qusaiba Shale, a widespread organic-rich shale that was deposited following regional deglaciation in the Early Silurian. Migration occurred regionally updip through Unayzah Formation reservoirs from the underlying Qusaiba Shale subcrop and/or vertically along fault-bounded zones on the flanks of structures from the underlying Qusaiba Shale. Interbedded Upper Permian shales and evaporites provide a top seal for the Unayzah and form the basal sequence of the overlying transgressive Khuff carbonate.

Pre-Qusaiba reservoir targets include the Cambrian-Ordovician Saq Sandstone, the Ordovician Qasim Formation, and Upper Ordovician to Lower Silurian periglacial clastics of the Zarqa and Sarah formations. High-gravity, low-sulfur oil has also been discovered in this pre-Qusaiba clastic section. The reservoirs of the pre-Qusaiba structures are fault bounded and sources laterally by the down-faulted Qusaiba Shale.