Abstract
The Sirt Basin exhibits a diverse and regionally extensive reservoir framework comprising carbonate, siliciclastic, and fractured-basement reservoirs of Mesozoic to Cenozoic age, generally occurring at burial depths of approximately 1,600–2,700 m. Its petroleum systems incorporate organic-rich source-rock intervals of Triassic, Cretaceous, and Paleocene age, including, in stratigraphic succession, the Mid-Nubian Shale, Etel, Rachmat, Sirte Shale, Kalash, and Hagfa Shale formations. These source rocks reflect marine, lacustrine, and terrestrial depositional influences and encompass predominantly B, C, and D/E organofacies, which exert a fundamental influence on hydrocarbon generation potential, petroleum composition, and charge-phase characteristics. Geochemical data indicate substantial source-rock generative capacity, with reported present-day average total organic carbon (TOC) values reaching 4 wt.% and average hydrogen index (HI) values of up to 650 mg HC/g TOC. Regionally variable transformation and expulsion efficiencies exceed 60%, indicating effective hydrocarbon generation and expulsion in suitably mature source-rock intervals, although advanced maturity and postmature conditions may locally reduce remaining generative potential. The regional sealing framework is dominated by thick shale successions and anhydrite-bearing lithofacies, which, together with the basin's complex fault architecture, governs hydrocarbon containment, migration pathways, and trap effectiveness. Integrated petroleum-system interpretation suggests spatially variable charge and accumulation histories, involving light-hydrocarbon generation in the western and eastern troughs and deeper parts of the northern central basin, followed by temporally variable migration and entrapment. The distribution of petroleum charge and accumulation is further influenced by structural configuration, fault connectivity, and the development of thick Cenozoic carbonate buildups in both onshore and offshore settings. Despite extensive exploration and development, the Sirt Basin retains significant remaining petroleum prospectivity. The most promising opportunities include deep onshore troughs, where light oil may remain an important exploration target, and deep to ultra-deep offshore plays, where thermogenic gas may constitute a major exploration objective. These findings highlight the importance of integrating regional basin architecture, source-rock maturity, petroleum generation and expulsion, migration connectivity, reservoir distribution, and seal effectiveness to refine petroleum-system models and improve the spatial prediction of remaining hydrocarbon potential across the Sirt Basin.