Hydrocarbon potential of Ordovician–Silurian successions in Akkas field, western desert of Iraq

Clay Minerals and Organic Matter from Deeply Buried Ordovician-Silurian Shale in Western Iraq: Implications for Maturity and Hydrocarbon Generation

“…Whereas shales in the Silurian Akkas Formation are black, fissile, calcareous, bituminous, pyritespotted, and organic-rich with TOC values ranging between 1.0 -16.6% in the Akkas-1 well [20]. The "hot" shale units (Figure-2) are likely to form the principal hydrocarbon source rock in the Palaeozoic sequence of western Iraq and were deposited mostly under anoxic conditions [22,23,25,28].…”

“…The Akkas-1 well in western Iraq (Figure-1) contains the most complete Ordovician and Silurian succession in Iraq and was designated as the subsurface reference section for the Ordovician Khabour and Silurian Akkas Formations, comprising an interbedded succession of sandstones and shale between 1463 m and the total depth of 4238 m [18][19]. Based on their economic and depositional significance, the shales in the Khabour and Akkas Formations were described in numerous papers, theses and reports [18][19][20][21][22][23][24][25]. Most of these works focus on the stratigraphy, depositional evolution, palynostratigraphy, organic geochemistry, hydrocarbon potential and exploration of Paleozoic prospects in western Iraq.…”

“…Concerning source rock potential of the Paleozoic source rocks in Iraq, Aqrawi et al (2010) [26] revealed that the lower Ordovician shales (assigned to Member 7 of the Khabour Formation, according to Al-Hadidy, 2007, [18]) and the lower Silurian ("hot" shale of the Akkas Formation) could be regarded as principal hydrocarbon source rocks in the Paleozoic sequence of western Iraq, similar to their role across the region in Jordan Syria, Libya, and Saudi Arabia [27,23,25]. The lower "hot" shale unit of the Silurian Akkas Formation, western Iraq, has an average-good source rocks (TOC 1.2-5.25 wt%, mean 2.2 wt%; S2 1.2-8.7 kg/tonne, mean 4.2 kg/tonne) [28].…”

Review of the Lower-Palaeozoic Reservoir Prospectivity of W. Iraq With Reference to Jordan

“…In the Akkas-1 well, light oil (42° API) was discovered in fractured sandstones and siltstones of the Qaim member, which has been assumed to be sourced from the hot shale of the underlying Hoseiba Member (Al-Habba et al 1994 andAl-Juboury et al 2019). Al-Khafaji et al (2015) concluded that only the Khabour Formation can be regarded as source for the gas and condensate in the Akkas field, whereas the hot shales of the Akkas Formation have not reached a sufficient maturation level in the well investigated. Mohammed et al (2020) concluded that the black shales of Khabour Formation are fair source rocks, highly matured and reached the peak of gas generation.…”

“…The Lower Palaeozoic succession is thus a primary exploration target with some discoveries in Ordovician and Silurian sandstones (e.g. Al-Haba et al 1994;Aqrawi, 1998;Al-Hadidy,2007;Tamar-Agha, 2009;Al-Ameri, 2010;Aqrawi et al 2010;Al-Khafaji et al 2015;Al-Juboury et al 2019;Abdula et al 2020 andMohammed et al 2020) where it is thick in both eastern Jordan and western Iraq ( Figs. 2A & 2B).…”