Changes

When considering the distribution of the giant oil and gas fields, two major groups of sedimentary basins can be identified: one in North Africa mainly dominated by rift, sag, and passive margins, and one in the Middle East, where oil fields are mainly preserved in sag and passive margin and collision-related basins.<ref name=Alhusseini_2000>Al-Husseini M.I. and Moujahed, I., 2000, Late Permian to Holocene paleofacies: Evolution of the Arabian Plate and its hydrocarbon occurrences: GeoArabia, v. 5, no. 4, p. 527–542.</ref> <ref name=Ziegler_2001>Ziegler, M. A., 2001, Late Permian to Holocene paleofacies: Evolution of the Arabian plate and its hydrocarbon occurrences: GeoArabia, v. 6, no. 3, p. 445–504.</ref> In the latter sector, oil fields are clustered in two major sets: Eastern Arabia-Persian Gulf-Zagros and Caspian Sea.

When considering the distribution of the giant oil and gas fields, two major groups of sedimentary basins can be identified: one in North Africa mainly dominated by rift, sag, and passive margins, and one in the Middle East, where oil fields are mainly preserved in sag and passive margin and collision-related basins.<ref name=Alhusseini_2000>Al-Husseini M.I. and Moujahed, I., 2000, Late Permian to Holocene paleofacies: Evolution of the Arabian Plate and its hydrocarbon occurrences: GeoArabia, v. 5, no. 4, p. 527–542.</ref> <ref name=Ziegler_2001>Ziegler, M. A., 2001, Late Permian to Holocene paleofacies: Evolution of the Arabian plate and its hydrocarbon occurrences: GeoArabia, v. 6, no. 3, p. 445–504.</ref> In the latter sector, oil fields are clustered in two major sets: Eastern Arabia-Persian Gulf-Zagros and Caspian Sea.

North Africa experienced several stages of alternating passive margin (e.g., Devonian, Carboniferous) and rift settings, related to different geodynamic events (e.g., effects of the Tethys opening in late Paleozoic) which recurred in this area. Rift and passive margin stages are commonly separated by local or regional compressional events (e.g., Cretaceous) with reactivation/inversion of extensional structures (Boote et al., 1998). Favorable environmental conditions controlled the deposition of major source rocks, such as the Hot Shale during the Silurian. This unit reflects the environmental changes (warming and sea-level rise) that postdated the Ordovician glaciations (Figure 3). The history of repeated rifting, sag stage, and folding favored the creation of a large number of stratigraphic and tectonic traps that store, at different stratigraphic levels, several giant fields.<ref name=Booteetal_1998>Boote, D., Clark-Lowes, D., and Traut M., 1998, Palaeozoic petroleum systems of North Africa, in D. Macgregor, R. Moody, and D. Clark-Lowes, eds., Petroleum geology of North Africa: GSL Special Publication 132, p. 7–68.</ref> <Macgregor_1998>Macgregor, D., 1998, Giant fields, petroleum systems, and exploration maturity of Algeria, in D. Macgregor, R. Moody, and D. Clark-Lowes, eds., Petroleum geology of North Africa: GSL Special Publication 132, p. 79–96.</ref> The presence of a wide, shallow-water shelf in an arid environment (Triassic-Jurassic) led to the deposition of thick and widespread salt layers, which represent an effcient seal at the regional scale.<ref name=Booteetal_1998 />

North Africa experienced several stages of alternating passive margin (e.g., Devonian, Carboniferous) and rift settings, related to different geodynamic events (e.g., effects of the Tethys opening in late Paleozoic) which recurred in this area. Rift and passive margin stages are commonly separated by local or regional compressional events (e.g., Cretaceous) with reactivation/inversion of extensional structures (Boote et al., 1998). Favorable environmental conditions controlled the deposition of major source rocks, such as the Hot Shale during the Silurian. This unit reflects the environmental changes (warming and sea-level rise) that postdated the Ordovician glaciations (Figure 3). The history of repeated rifting, sag stage, and folding favored the creation of a large number of stratigraphic and tectonic traps that store, at different stratigraphic levels, several giant fields.<ref name=Booteetal_1998>Boote, D., Clark-Lowes, D., and Traut M., 1998, Palaeozoic petroleum systems of North Africa, in D. Macgregor, R. Moody, and D. Clark-Lowes, eds., Petroleum geology of North Africa: GSL Special Publication 132, p. 7–68.</ref> <ref name=Macgregor_1998>Macgregor, D., 1998, Giant fields, petroleum systems, and exploration maturity of Algeria, in D. Macgregor, R. Moody, and D. Clark-Lowes, eds., Petroleum geology of North Africa: GSL Special Publication 132, p. 79–96.</ref> The presence of a wide, shallow-water shelf in an arid environment (Triassic-Jurassic) led to the deposition of thick and widespread salt layers, which represent an effcient seal at the regional scale.<ref name=Booteetal_1998 />

If in North Africa the basins are mainly related to rift basins followed by passive margin, the accretion of the peri-Gondwanan blocks to the southern margin of Eurasia led to the formation of a major concentration of giant fields along the northern passive margin of the peri-Gondwanan blocks and in the overlying peripheral basins related to their collision. In the southern Caspian Sea area, the giant fields are mainly stored in collision-related basins<ref name=Mannetal_2003 /> whose origin was controlled by the docking of the peri-Gondwanan along the southern margin of Eurasia (e.g., Cimmerian orogeny). A similar origin is suggested for the Northern Caucasus Basins,<ref name=Mannetal_2003 /> whereas a complex history (from cratonic backarc extension and rifting followed by a sag basin stage) is recorded in the Pricaspian Basin.<ref name=Weberetal_2003>Weber, L. J., Francis, B. P., Harris, P. M., and Clark, M., 2003, Stratigraphy, facies, and reservoir distribution, Tengiz Field, Kazakhstan, in W. M. Ahr, P. M. Harris, W. A. Morgan, and I. D. Somerville, eds., Permo- Carboniferous carbonate platforms and reefs: SEPM Special Publication 78 and AAPG Memoir 83, p. 351–394.</ref>

If in North Africa the basins are mainly related to rift basins followed by passive margin, the accretion of the peri-Gondwanan blocks to the southern margin of Eurasia led to the formation of a major concentration of giant fields along the northern passive margin of the peri-Gondwanan blocks and in the overlying peripheral basins related to their collision. In the southern Caspian Sea area, the giant fields are mainly stored in collision-related basins<ref name=Mannetal_2003 /> whose origin was controlled by the docking of the peri-Gondwanan along the southern margin of Eurasia (e.g., Cimmerian orogeny). A similar origin is suggested for the Northern Caucasus Basins,<ref name=Mannetal_2003 /> whereas a complex history (from cratonic backarc extension and rifting followed by a sag basin stage) is recorded in the Pricaspian Basin.<ref name=Weberetal_2003>Weber, L. J., Francis, B. P., Harris, P. M., and Clark, M., 2003, Stratigraphy, facies, and reservoir distribution, Tengiz Field, Kazakhstan, in W. M. Ahr, P. M. Harris, W. A. Morgan, and I. D. Somerville, eds., Permo- Carboniferous carbonate platforms and reefs: SEPM Special Publication 78 and AAPG Memoir 83, p. 351–394.</ref>