Changes

[[Paleozoic Petroleum System]]s: A summary of the PPS is shown in [[:file:M114CH01FG04.jpg|Figure 4]]. This petroleum system contains the basal [[Silurian]] Qusaiba hot [[shale]], and to a lesser extent the Qusaiba warm [[shale]]s, as its principal source rocks, with reservoirs extending from the [[Ordovician]] to the early [[Triassic]]. [[Seal]]s occur at different stratigraphic levels, with the evaporitic [[Sudair Formation]] of the early [[Triassic]] age serving as the regional top seal of the PPS. Hanadir and Ra’an shales of the [[Ordovician]] [[Qasim Formation]] may also present some source potential.

[[Paleozoic Petroleum System]]s: A summary of the PPS is shown in [[:file:M114CH01FG04.jpg|Figure 4]]. This petroleum system contains the basal [[Silurian]] Qusaiba hot [[shale]], and to a lesser extent the Qusaiba warm [[shale]]s, as its principal source rocks, with reservoirs extending from the [[Ordovician]] to the early [[Triassic]]. [[Seal]]s occur at different stratigraphic levels, with the evaporitic [[Sudair Formation]] of the early [[Triassic]] age serving as the regional top seal of the PPS. Hanadir and Ra’an shales of the [[Ordovician]] [[Qasim Formation]] may also present some source potential.

Source Rocks: Although several intervals of fine [[clastic]]s (e.g., [[shale]]s and [[mudstone]]) are potential source rocks of various organic richness, the basal hot [[shale]] member of the [[Qusaiba Formation]] of the [[Qalibah Group]] ([[:file:M114CH01FG02.jpg|Figure 2]]) shows a basin-wide occurrence ([[:file:M114CH01FG01.jpg|Figure 1]]) and is organic rich (Cole et al., 1994<ref name=Coleetal1994 />). Termination of [[glaciation]] at the end of the [[Ordovician]] resulted in a major sea-level rise during the early [[Silurian]] time, leading to deposition of the upward-coarsening [[progradation]]al [[Qalibah Group]]. This rapid [[transgression]] caused displacement of earlier shallow marine [[siliciclastic]]s and resulted in the deposition of organic-rich sediments within [[anoxic]] intra-shelf depressions of the northern [[Gondwana]] (Jones and Stump, 1999<ref name=Jonesandstump1999>Jones, P. J., and T. Stump, 1999, Depositional and tectonic setting of the Lower Silurian hydrocarbon source rock facies, Central Saudi Arabia: AAPG Bulletin, v. 83, p. 314–332.</ref>). As these intra-shelf depressions were filled with [[anoxic]] [[sediment]]s, more [[oxic]] depositional environment led to a widespread deposition of warm, organic-lean [[shale]]s of the [[Qusaiba Formation]] (Lüning et al., 2000<ref name=Lüningetal2000>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>). The organic-rich basal hot [[shale]] of the [[Qusaiba Formation]] is best developed in the subsurface of east-central [[Saudi Arabia]], as well as in the northwest Saudi Arabia, and has an average [[TOC]] content of about 5 wt.%, with maximum values as high as 20 wt.% (Cole et al., 1994<ref name=Coleetal1994 />). Several [[Paleozoic]] oil and gas fields in [[Saudi Arabia]] are known to have been sourced from the basal Qusaiba hot [[shale]] (AbuAli et al., 1991<ref name=Abualietal1991>AbuAli, M. A., U. A. Franz, J. Shen, F. Monnier, M. D. Mahmoud, and T. M. Chambers, 1991, Hydrocarbon generation and migration in the Paleozoic sequence of Saudi Arabia: Society of Petroleum Engineers, SPE 21376, p. 345–356.</ref>, 1999<ref name=AbuAlietal1999>AbuAli, M. A., J. L. Rudkiewicz, J. G. McGillivray, and F. Behar, 1999, Paleozoic petroleum system of Central Saudi Arabia: GeoArabia, v. 4, no. 3, p. 321–335.</ref>; Mahmoud et al., 1992<ref name=Mahmoudetal1992>Mahmoud, M. D., D. Vaslet, and M. I. Al-Husseini, 1992, The Lower Silurian Qalibah Formation of Saudi Arabia: An important hydrocarbon source rock: AAPG Bulletin, v. 76, p. 1491–1506.</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>; Cole et al., 1994<ref name=Coleetal1994 />; Jones and Stump, 1999<ref name=Jonesandstump1999 />). This hot shale unit contains type II amorphous organic matter, with [[graptolite]] and [[chitinozoan]]s, and ranges in thickness from 10 to 250 ft (3–70 m) as given by Mahmoud et al. (1992)<ref name=Mahmoudetal1992 />, Wender et al. (1998)<ref name=Wenderetal1998 />, AbuAli et al. (1999)<ref name=AbuAlietal1999 />, and AbuAli and Littke (2005)<ref name=Abualiandlittke2005>AbuAli, M. A., and R. Littke, 2005, Paleozoic petroleum systems of Saudi Arabia: A basin modeling approach: Geo-Arabia, v. 10, no. 3, p. 131–168</ref>. Within the [[Qusaiba Formation]], a thick sequence of nonradioactive, light to medium gray [[shale]] overlies the basal hot shale. This lean shale still contains poor to moderate [[organic]] richness (up to a few weight percent [[TOC]]) with mixed oil and gas potential (Cole et al., 1994)<ref name=Coleetal1994 />, and due to its thickness, it can also be a volumetrically important source rock for [[hydrocarbon]] resources in [[Saudi Arabia]].

Source Rocks: Although several intervals of fine [[clastic]]s (e.g., [[shale]]s and [[mudstone]]) are potential source rocks of various organic richness, the basal hot [[shale]] member of the [[Qusaiba Formation]] of the [[Qalibah Group]] ([[:file:M114CH01FG02.jpg|Figure 2]]) shows a basin-wide occurrence ([[:file:M114CH01FG01.jpg|Figure 1]]) and is organic rich (Cole et al., 1994<ref name=Coleetal1994 />). Termination of [[glaciation]] at the end of the [[Ordovician]] resulted in a major sea-level rise during the early [[Silurian]] time, leading to deposition of the upward-coarsening [[progradation]]al [[Qalibah Group]]. This rapid [[transgression]] caused displacement of earlier shallow marine [[siliciclastic]]s and resulted in the deposition of organic-rich sediments within [[anoxic]] intra-shelf depressions of the northern [[Gondwana]] (Jones and Stump, 1999<ref name=Jonesandstump1999>Jones, P. J., and T. Stump, 1999, Depositional and tectonic setting of the Lower Silurian hydrocarbon source rock facies, Central Saudi Arabia: AAPG Bulletin, v. 83, p. 314–332.</ref>). As these intra-shelf depressions were filled with [[anoxic]] [[sediment]]s, more [[oxic]] depositional environment led to a widespread deposition of warm, organic-lean [[shale]]s of the [[Qusaiba Formation]] (Lüning et al., 2000<ref name=Lüningetal2000>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>). The organic-rich basal hot [[shale]] of the [[Qusaiba Formation]] is best developed in the subsurface of east-central [[Saudi Arabia]], as well as in the northwest Saudi Arabia, and has an average [[TOC]] content of about 5 wt.%, with maximum values as high as 20 wt.% (Cole et al., 1994<ref name=Coleetal1994 />). Several [[Paleozoic]] oil and gas fields in [[Saudi Arabia]] are known to have been sourced from the basal Qusaiba hot [[shale]] (AbuAli et al., 1991<ref name=Abualietal1991>AbuAli, M. A., U. A. Franz, J. Shen, F. Monnier, M. D. Mahmoud, and T. M. Chambers, 1991, Hydrocarbon generation and migration in the Paleozoic sequence of Saudi Arabia: Society of Petroleum Engineers, SPE 21376, p. 345–356.</ref>, 1999<ref name=Abualietal1999>AbuAli, M. A., J. L. Rudkiewicz, J. G. McGillivray, and F. Behar, 1999, Paleozoic petroleum system of Central Saudi Arabia: GeoArabia, v. 4, no. 3, p. 321–335.</ref>; Mahmoud et al., 1992<ref name=Mahmoudetal1992>Mahmoud, M. D., D. Vaslet, and M. I. Al-Husseini, 1992, The Lower Silurian Qalibah Formation of Saudi Arabia: An important hydrocarbon source rock: AAPG Bulletin, v. 76, p. 1491–1506.</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>; Cole et al., 1994<ref name=Coleetal1994 />; Jones and Stump, 1999<ref name=Jonesandstump1999 />). This hot shale unit contains type II amorphous organic matter, with [[graptolite]] and [[chitinozoan]]s, and ranges in thickness from 10 to 250 ft (3–70 m) as given by Mahmoud et al. (1992)<ref name=Mahmoudetal1992 />, Wender et al. (1998)<ref name=Wenderetal1998 />, AbuAli et al. (1999)<ref name=AbuAlietal1999 />, and AbuAli and Littke (2005)<ref name=Abualiandlittke2005>AbuAli, M. A., and R. Littke, 2005, Paleozoic petroleum systems of Saudi Arabia: A basin modeling approach: Geo-Arabia, v. 10, no. 3, p. 131–168</ref>. Within the [[Qusaiba Formation]], a thick sequence of nonradioactive, light to medium gray [[shale]] overlies the basal hot shale. This lean shale still contains poor to moderate [[organic]] richness (up to a few weight percent [[TOC]]) with mixed oil and gas potential (Cole et al., 1994)<ref name=Coleetal1994 />, and due to its thickness, it can also be a volumetrically important source rock for [[hydrocarbon]] resources in [[Saudi Arabia]].

Reservoir Rocks: The main reservoirs of the [[Paleozoic Petroleum System|PPS]] are the sandstones of the [[Devonian]] [[Jauf Formation]], sandstones of the [[Permian]] [[Unayzah Formation]], and [[carbonate]]s of the [[Permian]] [[Khuff Formation]] ([[:file:M114CH01FG02.jpg|Figure 2]]). The [[Ordovician]] [[Sarah Formation]], underlying the regional Qusaiba hot [[shale]] source rock, consists mainly of fine- to coarse-grained [[sandstone]] sequences of glacial and glacio-fluvial origin. The formation is widely distributed in central and northwestern [[Saudi Arabia]]. Cantrell et al. (2014<ref name=Cantrelletal2014 />) has noted that pre-Qusaiba clastics (e.g., [[Sarah sandstones]]) are generally considered to be tight due to advanced [[diagenesis]], particularly cementation by [[quartz]] overgrowths, which has reduced reservoir quality.

Reservoir Rocks: The main reservoirs of the [[Paleozoic Petroleum System|PPS]] are the sandstones of the [[Devonian]] [[Jauf Formation]], sandstones of the [[Permian]] [[Unayzah Formation]], and [[carbonate]]s of the [[Permian]] [[Khuff Formation]] ([[:file:M114CH01FG02.jpg|Figure 2]]). The [[Ordovician]] [[Sarah Formation]], underlying the regional Qusaiba hot [[shale]] source rock, consists mainly of fine- to coarse-grained [[sandstone]] sequences of glacial and glacio-fluvial origin. The formation is widely distributed in central and northwestern [[Saudi Arabia]]. Cantrell et al. (2014<ref name=Cantrelletal2014 />) has noted that pre-Qusaiba clastics (e.g., [[Sarah sandstones]]) are generally considered to be tight due to advanced [[diagenesis]], particularly cementation by [[quartz]] overgrowths, which has reduced reservoir quality.