Petroleum Potential of the Ghadamis Basin, Libya: A Reevaluation Leading to New Play/Prospect Identification

Letouzey, Patrick¹, André Reymond¹, Frederic Dartois¹, Romain Debarre¹, Yves Godart¹, Mahmoud Elbakai², Ibrahim Mriheel², Milad Ben-Rahuma², Abuagila El­Harbi², Omar Suliman², Mohamed El-Kelani² (1) Beicip-Franlab, Rueil Malmaison, France (2) Petroleum Research Centre, Tripoli, Libya

This paper summarizes a recent (2001-2004), fully integrated study of the petroleum potential of the Ghadamis Basin, Libya. It involves sedimentology, high-resolution stratigra­phy, seismic interpretation, well correlation, reservoir and seal identification, source rock and basin modeling, play type classification, risk analysis and exploration strategy. This regional study which covers an area of about 450km x 450 km is based on an updated data­base of 25 000 km of 2D seismic lines , 360 wells, core and outcrop descriptions, formation dating and geochemical analyses. More than 54 named fields and discoveries are known within this basin. The Lower Akakus formation (Upper Silurian) and the Tadrart - Ouan Kasa formations (Lower Devonian) are, up to now, the most prolific oil sections, with respective­ly 42% and 35% of the total expected hydrocarbon in place (HIIP). Other reservoir units are distributed in the Upper Ordovician (Mamuniyat), in the Middle and Upper Devonian and, to a lesser extend, in the Carboniferous and in the Triassic (Ras Hamia) sands. Most of the exploratory wells have oil and gas shows. Oil and gas accumulations have been discovered in pure structural traps and in complex structural-stratigraphic trap combinations. The study led to the good understanding of the hydrocarbon charge. Large volumes of hydrocarbons were generated and expelled from Lower Silurian (predominant) and Upper Devonian (sub­ordinate) source rocks and the timing of the hydrocarbon generation versus trapping is favourable. This efficient petroleum system associated with a good hydrocarbon charge should strengthen the exploration of the basin. Several new play types, which encompass large areas, bring new encouragements for the Ordovician and Devonian objectives and open a new promising theme in the exploration era.