Changes

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==Geological Settings==

==Geological Settings==

The geological history of the [[Arabian Basin]], which is a part of the [[Arabian Plate]] ([[:file:M114CH01FG01.jpg|Figure 1]]), has been discussed in detail (e.g., Powers et al., 1966<ref name=Powersetal1966>Powers, R. W., L. F. Ramirez, D. D. Redmond, and E. L. Elberg Jr., 1966, Geology of the Arabian peninsula, sedimentary geology of Saudi Arabia: USGS Professional Paper, 560-D, 150 p.</ref>; McGillivray and Al-Husseini, 1992; Alsharhan and Nairn, 1997; Wender et al., 1998; Al-Hajri and Owens, 2000; Al-Husseini, 2000; Konert et al., 2001; Sharland et al., 2001; Ziegler, 2001; Faqira et al., 2009; Cantrell et al., 2014 and references cited therein).  

The geological history of the [[Arabian Basin]], which is a part of the [[Arabian Plate]] ([[:file:M114CH01FG01.jpg|Figure 1]]), has been discussed in detail (e.g., Powers et al., 1966<ref name=Powersetal1966>Powers, R. W., L. F. Ramirez, D. D. Redmond, and E. L. Elberg Jr., 1966, Geology of the Arabian peninsula, sedimentary geology of Saudi Arabia: USGS Professional Paper, 560-D, 150 p.</ref>; McGillivray and Al-Husseini, 1992<ref name=McGillivrayandalhusseini1992>McGillivray, J. G., and M. I. Al-Husseini, 1992, The Paleozoic petroleum geology of central Arabia: AAPG Bulletin, v. 76, p. 1473–1490.</ref>; Alsharhan and Nairn, 1997<ref name=Alsharhanandnairn1997>Alsharhan, A. S. and A. E. M. Nairn, 1997, Sedimentary basins and petroleum geology of the Middle East: Elsevier Science B.V., Amsterdam, 843 p.</ref>; Wender et al., 1998<Wenderetal1998>Wender, L. E., J. W. Bryant, M. F. Dickens, A. S. Neville, and A. M. Al-Moqbel, 1998, Paleozoic (Pre-Khuff) hydrocarbon geology of the Ghawar Area, eastern Saudi Arabia: GeoArabia, v. 3, p. 273–302.</ref>; Al-Hajri and Owens, 2000<ref name=Alhajriandowens2000>Al-Hajri, S., and B. Owens, 2000, Sub-surface palynostratigraphy of the Palaeozoic of Saudi Arabia, in S. Al-Hajri and B. Owens, eds., Stratigraphic palynology of the Palaeozoic of Saudi Arabia: GeoArabia Special Publication 1, Gulf PetroLink, Bahrain, p. 10–17.</ref>; Al-Husseini, 2000<ref name=Alhusseini2000>Al-Husseini, M. I., 2000, Origin of the Arabian plate structures: Amar collision and Najd rift: GeoArabia, v. 5, no. 4, p. 527–542.</ref>; Konert et al., 2001<ref name=Konertetal2001>Konert, G., A. M. Afifi, S. A. Al-Hajri, and H. J. Droste, 2001, Paleozoic stratigraphy and hydrocarbon habitat of the Arabian plate: GeoArabia, v. 6, no. 3, p. 407–442.</ref>; Sharland et al., 2001<ref name=Sharlandetal2001>Sharland, P. R., R. Archer, D. M. Casey, R. B. Davies, S. H. Hall, A. P. Heward, et al. 2001, Arabian plate sequence stratigraphy: GeoArabia Special Publication 2, Gulf PetroLink, Bahrain, 371 p.</ref>; Ziegler, 2001<ref name=Ziegler2001>Ziegler, M. A., 2001, Late Permian to Holocene paleofacies evolution of the Arabian Plate and its hydrocarbon occurrences: GeoArabia, v. 6, p. 445–504.</ref>; Faqira et al., 2009<ref name=Faqiraetal2009>Faqira, M., M. Rademakers, and A. M. Afifi, 2009, New insights into the Hercynian orogeny, and their implications for the Paleozoic hydrocarbon system in the Arabian plate: GeoArabia, v. 14, no. 3, p. 199–228.</ref>; Cantrell et al., 2014<ref name=Cantrelletal2014>Cantrell, D. L., P. G. Nicholson, G. W. Hughes, M. A. Miller, A. G. Bhullar, S. T. Abdelbagi et al., 2014, Tethyan petroleum systems of Saudi Arabia, in L. Marlow, C. Kendall, and L. Yose, eds., Petroleum systems of the Tethyan region: AAPG Memoir 106, p. 613–639.</ref> and references cited therein).  

[[file:M114CH01FG01.jpg|300px|thumb|{{figure number|1}}Oil and gas fields in the Arabian Plate and distribution of Silurian Qusaiba shales beneath Hercynian unconformity (after Faqira et al., 2009<ref name=Faqiraetal2009>Faqira, M., M. Rademakers, and A. M. Afifi, 2009, New insights into the Hercynian orogeny, and their implications for the Paleozoic hydrocarbon system in the Arabian plate: GeoArabia, v. 14, no. 3, p. 199–228.</ref>). MA-I and MA-II show the two areas selected for a 2-D basin modeling study. The Unayzah fields contain oil sourced by Qusaiba shales.]]

[[file:M114CH01FG01.jpg|300px|thumb|{{figure number|1}}Oil and gas fields in the [[Arabian Plate]] and distribution of [[Silurian]] Qusaiba [[shale]]s beneath [[Hercynian]] unconformity (after Faqira et al., 2009<ref name=Faqiraetal2009 />). MA-I and MA-II show the two areas selected for a 2-D basin modeling study. The [[Unayzah]] fields contain oil sourced by Qusaiba shales.]]

Therefore, only a brief summary will be presented in this chapter, and for details the reader is referred to previous publications. The main tectonic phases that shaped the Arabian Plate include:

Therefore, only a brief summary will be presented in this chapter, and for details the reader is referred to previous publications. The main tectonic phases that shaped the [[Arabian Plate]] include:

* Precambrian (formation of the basement)

* [[Precambrian]] (formation of the [[basement]])

* Ordovician-Silurian Glaciation and Deglaciation (Qusaiba shales source rocks deposition)

* [[Ordovician]]-[[Silurian]] [[Glaciation]] and [[Deglaciation]] (Qusaiba shales source rocks deposition)

* Late Devonian to the early Carboniferous (Hercynian Orogeny structural event)

* Late [[Devonian]] to the early [[Carboniferous]] ([[Hercynian]] [[Orogeny]] structural event)

* Late Permian through the Jurassic Zagros Rifting (Gondwana supercontinent fragmentation and drift of the Arabian Plate to the equator with a favorable source and reservoirs pairs development)

* Late [[Permian]] through the [[Jurassic]] [[Zagros]] Rifting ([[Gondwana]] [[supercontinent]] fragmentation and [[drift]] of the [[Arabian Plate]] to the equator with a favorable source and reservoirs pairs development)

* Tertiary Zagros Orogeny (tilt of the Arabian Plate and Zagros thrusting)

* Tertiary [[Zagros]] [[Orogeny]] (tilt of the [[Arabian Plate]] and [[Zagros]] thrusting)

As evidenced from the sedimentary succession (Figure 2), throughout the Paleozoic era, clastic continental and shallow-marine sedimentation prevailed on a stable passive margin on the northeastern Gondwana. The Hercynian events of the Carboniferous affected the area, creating regional uplift, widespread erosion, and basement tectonism due to rejuvenation of the preexisting weaknesses in the basement (Konert et al., 2001). From the Permian to the Eocene, the area was a broad stable passive margin where the deposition of mainly shallow-water carbonates with minor anhydrites and shales occurred (Cantrell et al., 2014). Since the Oligocene, the northeastern part of the basin has been undergoing shortening as a consequence of collision of the Arabian Plate with Laurasia (Zagros Orogeny). The resulting flexure of the Arabian Plate underneath the Zagros fold and thrust belt created a wedge-shaped, low-angle (less than 2°) foreland basin (Figure 3), that has been the site of mixed evaporitic, carbonate, and clastic sedimentation.

[[file:M114CH01FG02.jpg|300px|thumb|{{figure number|2}}Generalized pre-[[Mesozoic]] [[stratigraphy|stratigraphic]] column for (A) northwest and (B) east-central Saudi [[Arabian Basin]].]]

With respect to the Paleozoic Petroleum System (PPS), early Silurian time has prime importance due to deposition of organic-rich (hot) shales in a large shelf area of the Gondwana covering present-day North Africa and the Arabian Peninsula (Klemme and Ulmishek, 1991). Lower Silurian organic-rich (hot) shales have generated about 80–90% of the Paleozoic sourced hydrocarbons in North Africa and the Arabian Peninsula (Klemme and Ulmishek, 1991). The lower hot shales, of the Qusaiba Formation of the Qalibah Group in Saudi Arabia, are major source rocks of the Paleozoic oil and gas accumulations in the Arabian Peninsula (Alsharhan and Nairn, 1997). In most cases, the shales were deposited directly above upper Ordovician periglacial sandstones during the initial early Silurian transgression that was a result of the melting of the late Ordovician ice cap (Luning et al., 2000).

 

 

With respect to the [[Paleozoic Petroleum System]] (PPS), early [[Silurian]] time has prime importance due to deposition of organic-rich (hot) [[shale]]s in a large shelf area of the [[Gondwana]] covering present-day [[North Africa]] and the [[Arabian Peninsula]] (Klemme and Ulmishek, 1991<ref name=Klemmeandulmishek1991>Klemme, H. D., and G. F. Ulmishek, 1991, Effective petroleum source rocks of the world: Stratigraphic distribution and controlling depositional factors: AAPG Bulletin, v. 75, p. 1809–1851.</ref>). Lower [[Silurian]] organic-rich (hot) [[shale]]s have generated about 80–90% of the [[Paleozoic]] sourced [[hydrocarbon]]s in [[North Africa]] and the [[Arabian Peninsula]] (Klemme and Ulmishek, 1991<ref name=Klemmeandulmishek1991 />). The lower hot [[shale]]s, of the [[Qusaiba Formation]] of the [[Qalibah Group]] in [[Saudi Arabia]], are major source rocks of the [[Paleozoic]] oil and gas accumulations in the [[Arabian Peninsula]] (Alsharhan and Nairn, 1997<ref name=Alsharhanandnairn1997 />). In most cases, the shales were deposited directly above upper [[Ordovician]] [[periglacial]] [[sandstone]]s during the initial early [[Silurian]] [[transgression]] that was a result of the melting of the late [[Ordovician]] [[ice cap]] (Lüning et al., 2000<ref name=Luningetal2000>Lüning, S., J. Craig, D. K. Loydell, P. Storch, and B. Fitches, 2000, Lower Silurian “hot shales” in North Africa and Arabia: Regional distribution and depositional model: Earth Science Reviews, v. 49, p. 121–200.</ref>).

==Petroleum systems==

==Petroleum systems==