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Saudi Arabian Jurassic Outcrops and Reservoir Equivalents

Hughes, Geraint W.1; Lindsay, Robert F.*1
(1) Geological Technical Services Division, Saudi Aramco, Dhahran, Saudi Arabia.

The Jurassic Shaqra Group represents the entire Jurassic stratigraphic succession of Saudi Arabia. This group of carbonates and evaporites is composed of seven formations that host 14 reservoirs, which upsection are: 1) Marrat Formation (Lower Jurassic-Toarcian), which contains the Marrat reservoir equivalent; 2) Dhruma Formation (Middle Jurassic-Bathonian-Bajocian), which contains the Faridah, Sharar, and Lower Fadhili reservoir equivalents; 3) Tuwaiq Mountain Formation (Middle Jurassic-Callovian), which contains the Upper Fadhili and Hadriya reservoir equivalents; 4) Hanifa Formation (Upper Jurassic-Oxfordian), which contains the Hanifa reservoir equivalent; 5) Jubaila Formation (Upper Jurassic-Kimmeridgian), which contains the lower to middle part of the Arab-D reservoir equivalent; 6) Arab Formation (Upper Jurassic-Kimmeridgian-Tithonian), which contains the upper part of the Arab-D reservoir and Arab-C, Arab-B, and Arab-A reservoir equivalents; and 7) Hith Formation (Upper Jurassic-Tithonian), which contains the Rimthan, Hith Stringer, and Manifa reservoir equivalents.

The complete Jurassic succession is well exposed in central Saudi Arabia along the Tuwaiq Mountain Escarpment west, beneath, and east of the city of Riyadh. Arab-D evaporites have undergone dissolution and retreated to form the Hith/Sulaiy Escarpment east of Riyadh, leaving behind the carbonate successions as collapse breccias. South of Riyadh, Arab-D carbonate outcrops are preserved in Wadi Nisah and further south near Hawtah.

Major disconformities separate each formation in the Lower and Middle Jurassic, of which their duration progressively decreases upsection, with subaerial exposure surfaces less common in the Upper Jurassic and contain the least amount of missing time. The Jurassic succession shallowed-upward from low-energy, deeper marine settings downsection and became more high-energy, shallow marine to more evaporitic upsection.

Interpreted sedimentological and micropaleontological analysis of Jurassic outcrops has provided highly informative insights to improve the overall understanding of controls on reservoir properties and prediction of reservoir development in cored sections.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California