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Hydrocarbon Characterization and Gas Potential of the Saudi Arabian Mesozoic and Paleozoic Previous HitPetroleumNext Hit Systems

By

 Mahdi Abu Ali1

(1) Aramco, Dhahran, Saudi Arabia

 Saudi Arabia's Paleozoic and Mesozoic Previous HitpetroleumNext Hit systems are discussed with respect to source rock generation potential and hydrocarbon geochemistry. Hydrocarbons found in both systems are extraordinarily distinct, suggesting the presence of an efficient seal separating the two systems. Carbon isotopes provided an excellent hydrocarbon-source rock correlation tool.

The Paleozoic Previous HitpetroleumNext Hit Previous HitsystemNext Hit consists of the Early Silurian "hot" basal Qusaiba shales as the principal source rock. The main reservoirs are the Devonian and Permo-Carboniferous sands and carbonates. The basal Khuff clastics are the regional seal for the Permian Khuff and Unayzah reservoirs, and interbedded shales for the Devonian Jauf reservoir. Hydrocarbons found in this Previous HitsystemNext Hit include non-associated gas in Eastern Arabia and extra light oil in Central Arabia.

The Mesozoic Previous HitpetroleumNext Hit Previous HitsystemNext Hit is made up of the Jurassic and Cretaceous sub-systems. Argillaceous carbonates of the Tuwaiq Mountain and Hanifa formations are the source rocks for the Jurassic Previous HitsystemNext Hit. Carbonates of the Arab, Manifa, Hanifa, Hadriyah and Fadhili are the main reservoirs. The pervasive Hith anhydrites are the major regional seal for the Jurassic Previous HitsystemNext Hit. Hydrocarbons found in this Previous HitsystemNext Hit are typically medium to light oil and associated gas. The Cretaceous Previous HitsystemNext Hit contains mainly two groups: light oil in the Shu'aiba carbonate reservoir of the Shaybah field, and heavy to medium oil in the Wasia clastic reservoirs of the offshore fields.

Based on basin modeling of the respective source rocks, Paleozoic hydrocarbon potential indicates gas in the Previous HiteastTop and south, and oil in Central Arabia, confirming the existing hydrocarbon finds. The Jurassic potential is oil for most of eastern Arabia and gas for southern Arabia. The potential for the Cretaceous section is mainly oil. Reconstruction of the basin's history along with hydrocarbon generation provided a regional interpretation of the oil and gas migration histories.