Exploration: What next in Libya?

As the dust begins to settle in Libya, what is the country's exploration potential? This article is extracted from a longer article by Jane Whalley in Geoexpro.



Libya has five major onshore hydrocarbon basins, three in the east and two in the west:

The Sirte Basin is the most productive, containing 16 giant oil fields and accounting for about two-thirds of Libyan oil production and 80% of the country's proven reserves. It is the youngest of the Libyan oil basins and is attributed to the collapse of a structural high that existed from around 400 Ma to 140 Ma. Early Cretaceous sediments in the basin were clastic, common in North Africa at the time, whilst from the Late Cretaceous to Tertiary carbonates predominated, along with large quantities of organic-rich sediments, which give rise to two major source rocks, the Rachmat and Sirte Shales. The geological structures are dominated by a series of horsts and grabens, but there is also potential in Nubian sandstone stratigraphic traps in the southern Sirte Basin.

About 25% of production comes from the Murzuk Basin of south-west Libya, about 800 km south of Tripoli, which forms a large intra-cratonic basin between Algeria, Niger and Chad, and has some 3,000m of sediments from Cambrian to Quaternary age. The Silurian-aged Tannezuft shale is the major source rock, and hydrocarbons have been found trapped in large anticlinal features which are not heavily faulted. Due to its remote position, lying predominantly in the Sahara, it is relatively unexplored and the infrastructure is poorly developed, but a number of important discoveries have been made there, including the giant Elephant field, which in 2010 was producing an average of 126 Mboepd.

The western Ghadames Basin stretches into neighbouring Algeria where the sediment thickness reaches about 7,000m and where the majority of the basin's discovered reserves are located, reservoired in Silurian and Devonian rocks. Areas of particular exploration potential in this basin include late Ordovician glacial deposits.

The Cyrenaica Platform in north-east Libya to the east of the city of Benghazi has no commercial discoveries but has potential in the form of a series of troughs and uplifted blocks.

A number of discoveries have been made offshore, which accounts for the remaining production, mostly from the Pelagian Shelf Basin near Tripoli. Success rates for discovery offshore are higher than onshore and the area is considered highly prospective, although predominantly for gas. Potential is also thought to reside in the Jurassic and Cretaceous of the offshore Sirte embayment.