Assessment of Undiscovered Oil and Gas of the Lower Silurian Qusaiba-Paleozoic Total Petroleum Systems of the Arabian Peninsula

By

Christopher J. Schenk¹, Richard M. Pollastro¹, Thomas S. Ahlbrandt¹

(1) U.S. Geological Survey, Denver, CO

 The Lower Silurian Qusaiba Member of the Qalibah Formation was deposited over the northern and eastern part of the Paleozoic passive margin that now forms the eastern part of the Arabian Peninsula. The Qusaiba Member is a major source rock for hydrocarbons from the Wadi-Surhan Basin in the north to the Rub al Khali Basin in the south. The Qusaiba source rock in these basins is as much as 75 m thick, with TOC values ranging up to 20 weight percent, averaging about 4 weight percent. Qusaiba source rocks are generally mature or overmature for gas in the central parts of the basins, and are mature for oil along the margins of the basins, as demonstrated by the recent light oil fields discovered in central Saudi Arabia. Reservoirs are mainly carbonates of the Permian Khuff Formation and sandstones of Ordovician, Devonian, and Permian age. Six assessment units defined within the Lower Silurian Qusaiba-Paleozoic Total Petroleum Systems in the Arabian Peninsula were assessed for undiscovered petroleum resources, providing total mean estimates of 808 TCFG, 37 BBO, and 51 BBNGL. Most of the hydrocarbons discovered and produced to date from the Lower Silurian Qusaiba-Paleozoic Total Petroleum Systems have been gas in fields from the Qatar Arch and in fields along the extension of the Qatar Arch in Iran. Significant potential may exist in other areas, including the Rub al Khali Basin.