الفهرس 
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Abstract
ty-three Silurian cores and cuttings samples and 10 crude oil samples from the Ordovician reservoirs in the NC115 Concession, Murzuq Basin, southwest Libya were studied by optical and organic geochemical methods to determine source rock organic facies, conditions of deposition, thermal maturity and genetic relationships. The Lower Silurian Hot Shale at the base of the Tanezzuft Formation is a high-quality oil/gas-prone source rock that is currently within the early oil maturity window. The overall average TOC content of the Hot Shale is 7.23 wt% with a maximum recorded value of 20.9 wt%. By contrast, the overlying deposits of the Tanezzuft Formation have an average TOC of 0.62 wt% and a maximum value of 1.13 wt%. The organic matter in the Hot Shale consists predominantly of mixed algal and terrigenous Type-II/III kerogen whereas the rest of the formation is dominated by terrigenous Type-III organic matter with some Type II/III kerogen. Two palynofacies associations are recognized and described. The Hot Shale Palynofacies (PF-A): distal suboxic-anoxic environment, with Type-II>I kerogen (highly oil-prone). The Tanezzuft Formation Palynofacies (PF-B): distal suboxic-anoxic basin to mud-dominated oxic shelf (distal shelf) with Type-II/III kerogen (oil- and gas-prone). Chitinozoa, acritarchs and cryptospores date the Hot Shale as early–mid Rhuddanian (early Llandovery) within the Early Silurian, and the Tanezzuft Formation as late Rhuddanian–Telychian (Llandovery). Oils from the A-, B- and H-oilfields in the NC115 Concession were derived from marine shale source rocks that reflect deposition under suboxic to anoxic conditions: they contain mixed algal and terrigenous organic matter. The oils are light and sweet, and despite being similar, are almost certainly derived from different facies and maturation levels within mature source rocks. The NC115-B oils were generated from slightly less mature rocks than the others. Based on hierarchical cluster analysis (HCA), principal component analysis (PCA) and stable carbon isotope composition, the NC115 oils can be divided into two genetic families: Family-1 oils from Ordovician Mamuniyat reservoirs were probably derived from older Palaeozoic source rocks, whereas Family-2 oils from Ordovician Mamuniyat–Hawaz reservoirs were probably charged from a younger Palaeozoic source of relatively high maturity. A third family appears to be a mixture of the two but most similar to Family-2 oil. There is a good correlation between the Family-2 and -3 oils and the Hot Shale based on carbon isotope compositions. Saturated and aromatic maturity parameters indicate that these oils were generated from a source rock of considerably higher maturity than the rocks examined. The results imply that the oils originated from more mature source rocks outside the NC115 Concession and migrated to their current positions after generation.