Organic Petrological and Geochemical Evaluation of Jurassic Source Rocks from North Iraq
Mohamed M. El-Kammar
Geology Department, Faculty of Science, Cairo University, Egypt
Fuad S. Hussein
Geology Department, Salahaddin University, Iraq
Govand H. Sherwani
Ministry of Natural Resources, Kurdistan Region, Iraq
Keywords: Organic petrography, Geochemistry, Source rock, Jurassic, Kerogen, Bitumen, Iraq.
Abstract
Immature Jurassic oil shale is widely distributed and frequently outcropping in North Iraq. The organic-rich Jurassic sedimentary sequence, including prolific oil shale, was recorded in Banik area in Duhok Governorate of North Iraq. This sequence was systematically sampled from the geological formations; Sehkanyian, Sargelu and Naokelekan. The organic geochemical parameters were analyzed for 72 samples as well as one oil sample. A detailed study of petrologic properties was carried out for 12 samples. Based on TOC content, the Sargelu and Naokelekan formations can be considered as good to excellent source rocks, whereas Sehkanyian Formation has no potential since the TOC does not exceed 0.1 %. The samples of Sargelu and Naokelekan formations contain both kerogen types I and II indicating marine organic matter mainly derived from algae and phytoplankton organisms proposing typical oil prone source kerogen. This is further confirmed by the predominance of alginite and liptodetrinite macerals, where liptinite maceral group contribute more than 90% relative to other maceral contents. In general, Sargelu Formation samples have Production Index (PI), Tmax and fluorescence parameters (λmax and red/green quotient) suggesting immature to early mature stage of thermal maturity. The calculated ratios of Pr/Ph, Pr/nC17 and Ph/nC18for the extracted bitumen and the oil sample, suggest generation of bitumen from marine organic matter deposited under reducing conditions at an early thermal maturity stage.