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Hydrocarbon Generation Modeling of the Basrah Oil Fields, Southern Iraq

Al-Ameri, Thamer K.*1; Jafar, Mohammad S.2; Pitman, Janet 3
(1) College of Science, University of Baghdad, Baghdad, Iraq. (2) Ministry of Oil, Oil Exploration Co., Baghdad, Iraq. (3) U.S.Geological Survey, Denver, CO.

This paper discusses source rock characterization and the results of one-dimensional petroleum-system modeling of the Upper Jurassic and Lower Cretaceous section underlying prolific Cretaceous and Tertiary reservoirs in oil fields in southern Iraq. The study is based on well data of Majnoon, West Qurna, Nahr Umr, Zubair, and Rumaila oil fields. Burial history models indicate that Upper Jurassic source rocks began and ended oil generation in the Late Cretaceous to Paleogene. Lower to Middle Cretaceous source rocks, in turn, entered the oil window in the late Neogene and are continuing to generate today. The timing of petroleum generation is synchronous with the main tectonic events and trap formation associated with Late Cretaceous closure of the neo-Tethys, continent-continent collision associated with the Zagros orogeny, and Neogene opening of the Gulf of Suez and Red Sea.

Palynofacies and pyrolysis data provide important insights into the source rock potential of the Lower Cretaceous Sulaiy and Lower Yamama Formations and Upper Jurassic Najmah Formation. The extent to which Upper Jurassic source rocks contributed petroleum charge to younger Cretaceous reservoirs is uncertain because Upper Jurassic evaporites (Gotnia Formation) overlie Jurassic source facies and are regarded as a regional seal. The younger Cretaceous section contains only minor source rocks that were not buried deep enough for significant hydrocarbon generation.

 

AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain