Variations in the Degree of Catagenesis and Hydrocarbon Generation in the Source Rocks of the Sirt Basin, Libya

The thermal history of the Sirt Basin and realization of its hydrocarbon potential were modeled using the GALO numerical simulation system and a refined database of temperatures measured at various depths, vitrinite reflectance, and detailed data on vertical sections of the basin. These models are more accurate than preexisting basin models, which were underlain by the assumption that the temperature gradient remained unchanging throughout the whole evolutionary history of the basin. The burial history, temperature variations, and the maturity of organic matter in the sedimentary rocks of major tectonic structures in the Sirt Basin were numerically simulated with regard for multiple tectonic (stretching) and thermal reactivation of the lithosphere beneath the basin. The modeling was conducted for eight seismic sections arranged along a profile trending from east to west, from the Cyrenaica Platform in the eastern flank of the basin to the Hun graben in its western flank. Along with the traditionally analyzed Sirt source rocks of Campanian age, we analyze the outlooks of hydrocarbon generation in the pre-Campanian rocks. Our modeling results suggest that organic matter (OM) of Lower Cretaceous rocks in the Hameimat, Ajdabiya, and Maradah troughs was highly mature when some hydrocarbons (HC) could decompose into gas and coke in the course of their secondary cracking. The rocks of the Upper Cretaceous formations (95-65 Ma), including the widely known source rocks of the Sirt Shale, Formation, can be viewed as intensely generating oil within all modeled areas of the basin, except only the Hun graben and the Zelten and Dahra platforms.