Saharan Oil and Gas Basin

(Saharan-Libyan oil and gas basin), the largest oil and gas basin in Africa, located in Algeria, the southern border region of Tunisia, northern Libya, and northwestern Egypt. The Saharan oil and gas basin extends 3,600 km latitudinally and 800 km meridionally, for a total area of approximately 2.5 million sq km. In 1974, total basin reserves were estimated at 4.9 billion tons of petroleum and 3.9 trillion cu m of gas. The major petroleum deposits are at Hassi Mes-saoud in Algeria (initial recoverable reserves of 1,420 million tons) and Sarir (1,105 million tons), Amal (580 million tons), Jalo (558 million tons), and Zaltan (551 million tons) in Libya. Major gas deposits are at Hassi R’Mel (1.53 trillion cu m) and Rhourde Nauss (850 billion cu m) in Algeria. Exploration and analysis of the basin began in Algeria and Libya in the 1950’s and in Egypt in the 1970’s.

The Saharan oil and gas basin is a vast region of downwarping in the northern part of the Saharan Platform. It is bounded by the Ougarta intracratonic folded zone to the west, the Tuareg (Ahaggar) massif to the southwest, the Tibesti and al-Uwaynat massifs and the western tip of the Nubian-Arabian Shield to the southeast, the Suez graben to the east, and the folded Atlas system to the northwest. The eastern half of the basin is submerged in a northerly direction beneath the Mediterranean Sea. The basin’s cover is represented in cross-section by Paleozoic (4,000 m) and Cenozoic (500 m) terrigenous rocks and Mesozoic (5,500 m) saliferous and carbonate rocks. The cover fills a number of large cratonic depressions (Sirte, Illizi), which are separated by transverse block uplifts, often with protrusions of the foundation.

The principal petroleum and gas reserves are confined to Cambrian deposits: Ordovician, Devonian, Carboniferous, Triassic (gas). Cretaceous, and Paleogene. The reservoir rocks are primarily arenaceous rocks and limestones; they are sometimes of reef origin. Deposits are confined mainly to dome-shaped and brachyanticlinal folds, with producing horizons from 400 to 3,550 m deep. The petroleum is primarily light crude, ranging from 0.80 to 0.85 in density; there are few, if any, sulfur compounds, the average being 0.1 to 0.2 percent.

More than 200 petroleum deposits and more than 60 gas deposits have been found in the Saharan oil and gas basin. In 1973, 75 deposits produced a total of 157 million tons of petroleum and 30 billion cu m of gas. The prospects for finding new petroleum and gas deposits are linked to comprehensive analysis of various depressions and the adjacent water areas of the Mediterranean. The major petroleum and gas deposits in the basin are connected by a network of petroleum and gas pipelines to ports on the Mediterranean coasts of Algeria, Tunisia, and Libya and to the northeastern and southeastern regions of the Algerian Sahara.