The Ghadames Basin contains important oil-and gas-producing reservoirs distributed across Algeria, Tunisia, and Libya. Regional twodimensional (2-D) modeling, using data from more than 30 wells, has been undertaken to assess the timing and distribution of hydrocarbon generation in the basin. Four potential petroleum systems have been identified: (1) a Middle-Upper Devonian (Frasnian) and Triassic (Triassic Argilo Gréseux Inférieur [TAG-I]) system in the central-western basin; (2) a Lower Silurian (Tannezuft) and Triassic (TAG-I) system to the far west; (3) a Lower Silurian (Tannezuft) and Upper Silurian (Acacus) system in the eastern and northeastern margins; and (4) a Lower Silurian ( Tanezzuft) and Middle -Upper Devonian (Frasnian) system to the east-southeast. The Lower Silurian Tanezzuft source rock underwent two main phases of hydrocarbon generation. The first phase occurred during the Carboniferous, and the second started during the Cretaceous, generating most hydrocarbons in the eastern (Libyan) basin. The Frasnian shales underwent an initial, minor generative phase in the central depression during the Carboniferous. However, the main generation occurred during the Late Jurassic-Cenozoic in the western and central depression. The Frasnian shales are currently only marginally mature in the eastern part of the basin.Modeling indicates that the Alpine (Eocene) exhumation of the eastern (Libyan) basin margin had a significant control on the timing of hydrocarbon generation from the Lower Silurian source rock. The preferred burial-history model calibrates source rock maturity data by incorporating late exhumation and reduced subsidence

Constraining the burial history of a sedimentary basin is crucial for accurate prediction of hydrocarbon generation and migration. Although the Ghadames Basin is a prolific hydrocarbon province, with recoverable oil discovered to date in excess of 3.5 billion bbl, exploration on the eastern margin is still limited and the prospectivity of the area depends on the identification of effective source rocks and the timing of hydrocarbon generation. Sonic velocity, apatite fission track (FT) and vitrinite reflectance analysis offer three complementary methods to determine burial history and provide independent analytical techniques to evaluate the timing and amount of exhumation. The results indicate that two phases of tectonic activity had the biggest influence on basin evolution: the Hercynian (Late Carboniferous–Triassic) and Alpine (Late Mesozoic/Cenozoic) tectonic events. Exhumation during the Hercynian tectonic event increases from the SE, where an almost complete Palaeozoic section is preserved, towards the NW. This study quantifies the significant regional Alpine exhumation of the southern and eastern margins of the basin, with important implications for the timing of hydrocarbon maturation and expulsion, particularly for the Silurian source rock interval. Incorporating elevated Alpine exhumation values into burial history models for wells in the eastern (Libyan) part of the basin allows calibration with available maturity (Roeq) data using moderate values of Hercynian erosion. The result is preservation of the generation potential of Silurian (Tanezzuft) source rocks until maximum burial during Mesozoic/Cenozoic time, which improves the chance for preservation of hydrocarbon accumulations following entrapment.

Estimation of eroded overburden at unconformities is essential to accurately constrain burial histories and predict the timing of hydrocarbon maturation. In the Ghadames Basin, three independent techniques, palaeo-isopach construction, sonic velocity and vitrinite reflectance analysis, were employed. The resultant basin model suggests that only the two most significant unconformities, the Hercynian (Late Carboniferous) and Alpine (early Eocene), have a major control on timing of hydrocarbon charge.Modelling indicates only one period of generation from the Lower Silurian shales on the western margin of the basin, with 95% hydrocarbon generation prior to Hercynian exhumation. The central basin and southern margin experienced maximum burial during Eocene time. The Middle-Upper Devonian mudstones are the main source rocks and they did not generate significant volumes of hydrocarbons over the basin centre until Cretaceous time; they are currently within the peak oil generation zone.In Libya, on the eastern/northeastern flank of the basin, results indicate Cenozoic maximum burial, followed by up to 2000 m of Alpine exhumation. The magnitude of this exhumation has not been recognized previously, although it is a critical component of the basin model as it has a major impact on potential hydrocarbon charge in this area. Maturation models predict that the Lower Silurian source underwent two generative phases: (1) pre-Hercynian (Carboniferous) generation; and, significantly, (2) post-Hercynian (Late Jurassic-Cenozoic) generation. The identification of late hydrocarbon generation offers potential for oil and gas to migrate into post-Hercynian traps. Over the western, northern and eastern flanks, the Devonian source rocks remain immature/ marginally mature at present day.