Issues‎ > ‎vol19n1‎ > ‎

Source Rock Assessment of Naokelekan Formation in Iraqi Kurdistan

Rzger A. Abdula

Department of Petroleum Geosciences, Faculty of Science, Soran University, Soran, Kurdistan Region, Iraq



The Callovian-Kimeridgian Naokelekan Formation is a heterogeneous sequence consisting principally of bituminous shales with bituminous limestone and dolomitic limestones. It is 48 m thick maximally in some parts of the area. One hundred forty four rock and cutting samples from six outcrops and eight boreholes in different parts of Iraqi Kurdistan have been studied using the Rock-Eval technique with the primary purpose of assessing their potentiality as promising source rocks for petroleum. The outcomes of the Rock-Eval study for examined samples shows that TOC ranges from 0.4 to 18.8 wt. % and types II and III kerogens are the main components of organic matter.
Qualitative evaluations are also done by textural microscopy used in assessing amorphous organic matter for palynofacies. The organic matters are mature that have thermal alteration index of 2.6-3.2 by Pearson's scale with palynomorphs of dark orange and light brown colors and Tmax ranges between 434 to 493ºC. Thus the Naokelekan Formation can be considered as a source rock for generation and expulsion of oil and/or gas that has been charged largely oil fields in the area.
Maturity increases toward the northeastern part of the studied area. Furthermore, the study revealed that Naokelekan Formation is within dry gas and/or late oil zone in the eastern part, early oil window in the central part and immature in the western part of the studied area.

Key Words:
Source rock


[1] Bellen, R.C. Dunnington, van, H.V., Wetzel, R., and Morton, D.M. “Lexique Stratigraphic International”, Paris, Vol . III, Asie, Fascicule 10a Iraq, pp. 250-253. (1948).

[2] Altinli, I.E. “Geology of Eastern and Southeastern Anatolia, Turkey”, Bulletin of Mineral Research Exploration Institute of Turkey, Foreign Edition, Ankara, No. 60, pp. 35-76. (1966).

[3] Al-Omari, F.S. and Sadiq, A. “Geology of Northern Iraq”, Mosul University Press, Mosul, Iraq, 198 p. (in Arabic). (1977).

[4] Buday, T. “The Regional Geology of Iraq, Vol. 1, Stratigraphy and Paleogeography”, Dar Al-Kutub Publishing House, University of Mosul, Mosul, Iraq, 445 p. (1980).

[5] Al-Sayyab, A., Al-Ansari, N., Al-Rawi, D., Al-Jassim, J., Al-Omari, F., and Al-Shaikh, Z. “Geology of Iraq”, Mosul University Press, Mosul, Iraq, 280 p. (in Arabic). (1982).

[6] Odisho, K.Y and Othman, R.S. “Preliminary Geochemical Evaluation of Hydrocarbon Source Rocks in Northern Part of Iraq”, Iraqi Geological Journal, Vol. 25, pp. 136-153. (1992).

[7] Lewan, M.D. and Ruble, T.E. “Comparison of Petroleum Generation Kinetics by Isothermal Hydrous and Nonisothermal Open-System Pyrolysis”, Organic Geochemistry, Vol. 33, pp. 1457-1475. (2002).

[8] Pitman, J.K., Steinshouer, D., and Lewan, M.D. “Petroleum Generation and Migration in the Mesopotamian Basin and Zagros Fold Belt of Iraq, Results from a Basin-Modeling Study” GeoArabia, Gulf PetroLink, Bahrain, Vol. 9, No. 4, pp. 41-72. (2004).

[9] Jassim, S.Z. and Al-Gailani, M. “Hydrocarbons”, chapter 18, in: Jassim, S.Z., and J.C. Goff, eds., “Geology of Iraq”, first edition: Brno, Czech Republic, Prague and Moravian Museum, pp. 232-250. (2006).

[10] Ahmed, S.M. “Source Rock Evaluation of Naokelekan and Barsarin Formations (Upper Jurassic) Kurdistan Region/N. Iraq”, M.Sc. thesis (unpublished), Science College, University of Sulaimani, Sulaimani, Iraq, 174 p. (2007).

[11] Aqrawi, A.A.M., Horbury, A.D., Goff, J.C., and Sadooni, F.N. “The Petroleum Geology of Iraq”, Scientific Press Ltd., UK, 604 p. (2010).

[12] Al-Badry, A.M.S “Stratigraphy and Geochemistry of Jurassic Formations in Selected Sections–North Iraq”, Ph.D. dissertation (unpublished), Science College, University of Baghdad, Baghdad, Iraq, 183 p. (2012).

[13] Hussein, F.S., El Kammar, M.M., and Sherwani, G.H. “Organic Geochemical Assessment of Jurassic Source Rock from Duhok, North Iraq”, Journal of American Science, Vol. 9, No. 1, pp. 258-264. (2013).

[14] Al-Ameri, T.K., Al-Jubouri, N.M., Isa, M.J., and Al-Azzawi, R.E. “Hydrocarbons Generation Potential of the Jurassic–Lower Cretaceous Formation, Ajeel Field, Iraq”, Arabian Journal of Geosciences, Vol. 6, No. 10, pp. 3725–3735. (2013).

[15] Baban, D.H. and Ahmed, S.M. “Vitrinite Reflectance as a Tool for Determining Level of Thermal Maturity for the Upper Jurassic Naokelekan and Barsarin Formations in Sargelu Location, Kurdistan Region, NE Iraq”, Arabian Journal of Geosciences, Vol. 7, Issue 6, pp. 2269-2277. (2014).

[16] Sachsenhofer, R.F., Bechtel, A. Gratzer, R. and Raine, T.M. “Source-Rock Maturity, Hydrocarbon Potential and Oil-Source-Rock Correlation in Well Shorish-1, Erbil Province, Kurdistan Region, Iraq”, Journal of Petroleum Geology, Vol. 38, issue 4, pp. 357-381. (2015).

[17] Aqrawi, A.A.M. and Badics, B. “Geochemical Characterisation, Volumetric Assessment and Shale-Oil/Gas Potential of the Middle Jurassic–Lower Cretaceous Source Rocks of NE Arabian Plate”, GeoArabia, 2015, Vol. 20, No. 3, Gulf PetroLink, Bahrain, pp. 99-140. (2015).

[18] English, J.M., Lunn, G.A., Ferreira, L., and Yacu, G. “Geologic Evolution of the Iraqi Zagros, and Its Influence on the Distribution of Hydrocarbons in the Kurdistan Region”, AAPG Bulletin, Vol. 99, No. 2, pp. 231–272. (2015).

[19] Abdula, R.A. “Hydrocarbon Potential of Sargelu Formation and Oil-Source Correlation, Iraqi Kurdistan”, Arabian Journal of Geosciences, Vol. 8, Issue 8, pp. 5845-5868. (2015).

[20] Al-Ahmed, A.A.N. “Organic Geochemistry, Palynofacies and Hydrocarbon Potential of Sargelu Formation (Middle Jurassic) Northern Iraq”, Ph.D. dissertation (unpublished), Science College, University of Baghdad, Baghdad, Iraq, 120 p. (2006).

[21] Al-Ameri, T.K. and Zumberge, J. “Middle and Upper Jurassic Hydrocarbon Potential of the Zagross Fold Belt, North Iraq”, Marine and Petroleum Geology, Vol. 36, pp. 13-34. (2012).

[22] Al-Habba, Y.Q. and Abdullah, M.B. “A geochemical Study of Hydrocarbon Source Rocks in Northwestern Iraq”, Oil and Arab Cooperation Journal, Vol. 15, pp. 11-51 (in Arabic). (1989).

[23] Abdula, R.A. “Petroleum Source Rock Analysis of the Jurassic Sargelu Formation, Northern Iraq”, M.Sc. thesis (unpublished), Colorado School of Mines, Golden, Colorado, 106 p. (2010).

[24] Ameen, M.S. “Effect of Basement Tectonics on Hydrocarbon Generation, Migration, and Accumulation in Northern Iraq”, AAPG Bulletin, Vol. 76, No. 3, pp. 356-370. (1992).

[25] Jassim, S.Z. and Buday, T. “Units of the Unstable Shelf and the Zagros Suture”, chapter 6, in: Jassim, S.Z., and J.C. Goff, eds., “Geology of Iraq”, first edition: Brno, Czech Republic, Prague and Moravian Museum, pp. 71-83. (2006).

[26] Abdula, R.A., Balaky, S.M., Nurmohamadi, M.S., and Piroui M. “Microfacies Analysis and Depositional Environment of the Sargelu Formation (Middle Jurassic) from Kurdistan Region, Northern Iraq”, Donnish Journal of Geology and Mining Research, Vol. 1, No. 1, pp. 001-026. (2015).

[27] Salae, A.T.S. “Stratigraphy and Sedimentology of the Upper Jurassic Succession, Northern Iraq”, M.Sc. thesis (unpublished), Science College, University of Baghdad, Baghdad, Iraq, 95 p. (2001).

[28] Balaky, S.M.H. “Stratigraphy and Sedimentology of Sargelu Formation (Middle Jurassic) in Selected Sections in Erbil and Duhok Governorates–Iraqi Kurdistan”, M.Sc. thesis (unpublished), Science College, University of Salahaddin, Erbil, Iraq, 109 p. (2004).

[29] Alsharhan, A.S. and Nairn, A.E.M. “Sedimentary Basins and Petroleum Geology of the Middle East”, Elsevier Science B. V., Amsterdam, Netherlands, 843 p. (2003).

[30] Ditmar, V. and Iraqi-Soviet Team “Geological Conditions and Hydrocarbon Prospects of the Republic of Iraq (Northern and Central Parts) (manuscript report)”, Iraq National Oil Company, Baghdad, Iraq. (1971).

[31] Balaky, S. M. “Sequence Stratigraphic Analyses of Naokelekan Formation (Late Jurassic), Barsarin Area, Kurdistan Region–Northeast Iraq”, Arabian Journal of Geosciences, Vol. 8, Issue 8, pp. 5869-5878. (2015).

[32] Peters, K.E., “Guidelines for Evaluating Petroleum Source Rock Using Programmed Pyrolysis”, AAPG Bulletin, Vol. 70, No. 3, pp. 318-329. (1986).

[33] Hunt, J.M. “Petroleum Geochemistry and Geology”, second edition, New York, W.H. Freeman, and Company, 743 p. (1996).

[34] Peters, K.E. and Cassa, M.R. “Applied Source Rock Geochemistry”, Chapter 5, in Magoon, L.B., and W.G. Dow, eds. “The petroleum system—from source to trap”, AAPG Memoir 60, pp. 93-120. (1994).

[35] Dembicki Jr, H. “Three Common Source Rock Evaluation Errors Made by Geologists During Prospect or Play Appraisals”, AAPG Bulletin, Vol. 93, No. 3, pp. 341-356. (2009).

[36] Tissot, B.P. and Welte, D.H. “Petroleum Formation and Occurrence”, 2nd revised and enlarged edition, Berlin Heidelberg New York Tokyo, Springer-Verlag, 699 p. (1984).

[37] Reed, S. and Ewan, H.M. “Geochemical Report, Norse Hydro A/S, 6407/7-1”, Accessed February 8, 2010. (1986).

[38] Geologic Materials Center “Total Organic Carbon, Rock-Eval Pyrolysis, and Whole Oil Gas Chromatograms of Core from the Standard Alaska Production Co. Sag Delta 34633 No. 4 well (11,637–12,129) and from the Shell Oil Co. OCS Y-0197 (Tern No. 3) well (12,978-13,131)”, State of Alaska Geologic Materials Center Data Report no. 157, total of 4 pages in report, Accessed 2/14/2010. (1990).

[39] Pimmel, A. and Claypool, G. “Introduction to Shipboard Organic Geochemistry on the JOIDES Resolution”, ODP Tech. Note, 30 [Online], Available from World Wide Web:, Accessed 2/14/2010. (2001).

[40] Shaaban, F., Lutz, R., Littke, R., Bueker, C., and Odisho, K. “Source-Rock Evaluation and Basin Modeling in NE Egypt (NE Nile Delta and Northern Sinai)”, Journal of Petroleum Geology, Vol. 29, Issue 2, pp. 103-124. (2006).

[41] Espitalié, J., Deroo, G., and Marquis, F. “Rock-Eval Pyrolysis and Its Applications” Revue De L'institut Français Du Pétrole (IFP), Vol. 40, No. 5, pp. 563-579. (1985).

[42] Espitalié, J., Laporte, J.L., Madec, M., Marquis, F., Leplat, P., Paulet, J., and Boutefeu, A. “Rapid Method for Source Rocks Characterization and for Determination of Petroleum Potential and Degree of Evolution”, Revue De L'institut Français Du Pétrole (IFP), Vol. 32, No. 1, pp. 23-42. (1977).

[43] Dahl, B., Bojesen-Koefoed, J., Holm, A., Justwan, H., Rasmussen, E., and E. Thomsen, “A new Approach to Interpreting Rock-Eval S2 and TOC Data for Kerogen Quality Assessment”, Organic Geochemistry, Elsevier Ltd., Vol. 35, pp. 1461-1477. (2004).

[44] Allen, T.L., Fraser, T.A., and Osadetz, K.G. “Rock-Eval/TOC Data for 18 Wells, Peel Plateau and Plain, Yukon Territory (65º 50' to 67º 00' N; 133º 45' to 135º 15' W)”, Yukon Geological Survey, Open File 2008-1, 14 p. plus spreadsheet(s): Accessed 2/8/2010 (2008).

[45] Bacon, C.A., Calver, C.R., Boreham, C.J., Leaman, D.E., Morrison, K.C. Revill, A.T., and Volkman, J.K. “The Petroleum Potential of Onshore Tasmania–a Review”, Geological Survey Bulletin, 71, 93 p. (2000).

[46] Jarvie, D.M., Mbatau, F., Maende, A., Ngenoh, D., and Wavrek, D.A. “Petroleum Systems in Northwest Kenya”, Presented at the Annual Meeting of the American Association of Petroleum Geologists, Denver, CO. (2001).

[47] Pearson, D.L., “Pollen/Spore Color ‘Standard’ (Version.2)”, Bartlesville (Phillips Petroleum Company, Geology Branch). (1990).

[48] Huc, A.Y. and Hunt, J.M. “Generation and Migration of Hydrocarbons in Offshore South Texas Gulf Coast Sediments”, Geochemica et Cosmochimica Acta, printed in Great Britain, Vol. 44, pp. 1081-1089. (1980).

[49] Smith, J.T., “Petroleum System Logic as an Exploration Tool in a Frontier Setting”, Chapter 2, in Magoon, L.B., and Dow, W.G., eds. “The Petroleum System—from Source to Trap”, AAPG Memoir 60, Tulsa, pp. 25-49. (1994).