Basin Evolution and Geochemical Modeling
Western Desert study, Egypt
Postdoctoral Research by Dr Gianluca Badalini
Introduction:
This literature based pilot study on the Western Desert of Egypt is aimed to integrate structural and stratigraphic studies to assess the main themes of basin evolution, structural framework, regional stratigraphy and its effects on reservoir distribution and size, their formation and destruction, source nature and distribution, exploration potential.
Summary:
An increasing proportion of the Egyptian hydrocarbon production comes from the Western Desert. In the late 90's, oil production in the Western Desert accounted for about 16 % of Egypt's total oil production a day. The gas fields in the area produced 400 mm cmpd, an amount that accounted for 30% of the total gas production in the country.
The Western Desert of Egypt consists of a series of small rift basins. Some of them date back to the Permian, but the majority can be considered to have initiated in the Late Jurassic-Early Cretaceous, contemporaneously with the creation of the Mediterranean basins and with the southernmost Sirte rifts (Guiraud, 1998). Extensional tectonic activity was terminated in the Late Cretaceous by the Syrian arc inversion phase (MacGregor and Moody, 1998). The dominant structural style of the Western Desert comprises two systems: a deeper series of low-relief horst and graben belts, separated by master faults of large throw, and broad Late Tertiary folds at shallower depth (Sestini, 1995).
The stratigraphic succession of northern Egypt is characterized by several carbonate-clastic alternations that, together with the enclosed secondary transgressive-regressive cycles, constitute one of the main elements of the Mesozoic-Early Tertiary petroleum systems of the Western Desert (Sestini, 1995). The occurrence of oil is closely linked with the tectono-stratigraphic history of the area, which has created multiple reservoir and seal combinations. Adequate potential source rocks are stratigraphically and areally widespread in the Western Desert (Abu El Naga, 1984; Elzarka, 1983), with two major oil types identified in the northern Western Desert (Zein El Din et al., 1990). Most fields are related to structures formed in the Late Cretaceous-Eocene and are placed in, or at the edge of early depocentres that later became kitchen areas (Abu El Naga, 1984).
The Western Desert of Egypt still has a significant hydrocarbon potential as recent oil and gas discoveries indicate (for example in the Khalda Concession, Khatatba Formation). Results of new wells, combined with 3D seismic and additional geological interpretation, demonstrate that fields may be larger than previously thought.
References:
Guiraud, R., 1998, Mesozoic rifting and basin inversion along the northern African Tethyan margin: an overview, in D. S. MacGregor, Moody, R.T.J., Clark-Lowes, D.D., eds., Petroleum Geology of North Africa, London, Geological Society Special Publication, v. 132: p. 217-229.
MacGregor, D. S., Moody, R.T.J., 1998, Mesozoic and Cenozoic petroleum systems of North Africa, in D. S. MacGregor, Moody, R.T.J., Clark-Lowes, D.D., eds., Petroleum Geology of North Africa, London, Geological Society Special Publication, v. 132: p. 201-216.
Sestini, G., 1995, Egypt, in H. Kulke, ed., Regional Petroleum Geology of the World, Part II: Africa, America, Australia and Antarctica, Berlin-Stuttgart, Gebrüder Borntraeger: p. 57-87.
Abu el Naga, M., 1984, Palaeozoic and Mesozoic depocentres and hydrocarbon generating areas, Northern Western Desert: E.G.P.C. Eleventh Explor. & Prod. Conference, Cairo, p. 269-287.
Elzarka, M. H., 1983, Mode of hydrocarbon generation and prospects of the northern part of the Western Desert, Egypt: J. Afr. Earth Sci., v. 14, p. 294-318.
Zein El Din, M. Y., Matbouly, S.I., Moussa, S.M., Khalik, M.A., 1990, Geochemistry and oil-oil correlations in the Western Desert: Proceedings of the 10th Egyptian Petroleum Conference.