Libya’s 2025 bid round is a good sign of political stability and economic prospects in the country and will attract international oil companies. At the University of Utah’s Energy and Geoscience Institute I have been engaged in a major study of Libya’s petroleum basins. Here are some geologic reflections.
Flashback
In the first half of the 20th century, Italian geologists conducted pioneering mapping of Libya. In 1953 international oil companies began extensive oil exploration in Libya. The first commercial oil field, Bahi field in the Sirt basin, was discovered in 1958. The 1969 coup by Gaddafi led to nationalization of Libya’s oil and gas in 1970. Petroleum exploration and development were active in Libya until Gaddafi’s fall in 2011 which led to civil war and dual governance. In 2020, the two rival governments in east and west Libya signed a ceasefire and a unity government was established.
Tectonic Evolution
Libya’s location in north Africa – a key part of Gondwana supercontinent; facing the Mediterranean Sea; a vestige of the Tethys Ocean – indicates a protracted complex geologic history.
Tibesti Massif comprises the oldest exposed rocks in southern Libya that probably formed about one billion years ago but was extensively intruded by 550-500 million years’ granites of “Pan African” orogeny and affected by Oligocene volcanism.
After the Pan African orogeny assembled Gondwana in the southern hemisphere, a series of continental blocks broke and drifted away from the northern margin of Gondwana in the Early Paleozoic. During these times, the Libyan region was a rift-passive continental margin framed in several northwest-southeast trending swells and troughs and filled with mainly clastic sediments. Libya’s position in the South Pole during the Late Ordovician is reflected in its glacial sediments of this age. The passive margin basin subsidence continued until Carboniferous when Gondwana and Laurentia collided to form the supercontinent Pangea. This “Hercynian” or “Variscan” orogeny fashioned a series of northeast-southwest trending high and low structures in Libya.
From the Permian onward, the northern margin of Gondwana once again became a rift-passive continental margin facing the Neo-Tethys Ocean, and Gondwana moved northward. During the Triassic, Pangea began to fragment and the Mediterranean Sea began to take shape. In the Cretaceous, Apulia or the Adriatic continental block broke from northern Africa and collided with Eurasian plate across the Mediterranean Sea. This event was the onset of massive carbonate deposition in Libyan basins during the Cretaceous and Paleogene. The subduction of African plate beneath Eurasian plate and the resulting compressional stresses caused tectonic inversion of strata in parts of Libya.
Basins and Reservoirs
Libya’s five onshore basins are relatively well studied: Kufrah and Murzuq in the south; Ghadamis in the west, which continues to the Berkine-Illizi basin in Algeria; Sirt basin adjacent to the Western Desert of Egypt on the east, and Cyrenaica in the northeast. These basins are further divided into fault-bounded grabens (mini basins) and highs across which sedimentary thicknesses or facies vary.
The Kufrah, Murzuq and Ghadamis basins contain Paleozoic petroleum plays. Sirt, the most prolific basin, hosts Mesozoic and Paleogene plays, although it also has Cambrian-Ordovician reservoirs probably charged by Cretaceous source rocks. Cyrenaica platform contains Paleozoic, Mesozoic and Paleogene plays.
Several stratigraphic horizons mark regional source rocks or reservoirs. In the Paleozoic sections, Silurian formations are “hot shales” deposited during a major marine transgression, while Ordovician-Devonian sandstones provide excellent clastic reservoirs. The Mesozoic- Paleogene sections have multiple reservoir units, mainly carbonate rocks with effective shale source rocks of Aptian, Turonian, Santonian, Campanian and Ypresian age.
[1] 2025 Energy Institute Statistical Review of World Energy[2] 2021 BP Statistical Review of World Energy[3] 2025 OPEC Annual Statistical Bulletin
New Prospects
Libya has 320 discovered oil fields; however, these discoveries are distributed disproportionally. Nearly 75 percent of Libya’s giant fields were discovered before 1970. About 89 percent of Libya’s oil is concentrated in the Sirt basin.
Libya’s offshore basins in the Mediterranean Sea require detailed geophysical and petroleum system studies. It will be interesting to see if the recent oil and gas discoveries in the East Mediterranean basins can be extended to offshore Libya. The offshore Bouri field in the Tripolitania (Pelagian) basin, which produces oil from Eocene limestone, is a good sign for more discoveries in Libyan waters.
Unlike the Nile Delta in Egypt, the present water drainage in Libya is mainly by seasonal rivers (wadis). However, a recent study in the Journal of African Earth Sciences reported on an Oligocene-age deltaic system in northeast Sirt basin. Comparison and contrast between onshore and offshore basins will lead to both geological and hydrocarbon discoveries.
Libya’s new licensing round offers 128.7 thousand square kilometers of 11 offshore blocks and 106.6 thousand square kilometers of 11 onshore blocks. The country’s vision is to produce 2 to 3 million barrels of oil per day in the coming years. This will require substantial investments and new technological applications.