TECTONIC AND EROSION FEATURES, AND THEIR INFLUENCE ON ZONAL DISTRIBUTION OF THE UPPER TRIASSIC AND THE LOWER CRETACEOUS SEDIMENTS IN THE EUPHRATES GRABEN AREA, SYRIA

We have investigated the tectonic and erosion features of the Upper Triassic (Mulussa F Formation) and Lower Cretaceous (Rutbah Formation) sediments in the Euphrates graben area and analysed their influence on changes in the thickness and zonal distribution patterns of these sediments. In this study, the geological modeling software of Petrel Schlumberger is used to model the regional geological structure and stratigraphy from the available geological and geophysical data.

The Upper Triassic and Lower Cretaceous sediments (in total, almost 800 m thick) are the major hydrocarbon reservoirs in the Euphrates graben, which contain approximately 80 to 90 % of the total hydrocarbon reserve in this area. These sedimentary zones experienced variable changes in thickness and zonal distribution due to erosion processes caused by the two major regional unconformities, the Base Upper Cretaceous (BKU) and Base Lower Cretaceous (BKL) unconformities. The maximum thickness of the Upper Triassic sediments amounts to 480 m in the central parts of the Euphrates graben and along the NW-SE trend, i.e. in the dip direction of the Upper Triassic Mulussa F Formation. Towards the NE flank of the graben near the Khleissia uplift and the SW flank near to the Rutbah uplift, the thickness of the Upper Triassic sediments is gradually decreased due to their partial or total erosion caused by the BKL unconformity, and also due to a less space for sediment accumulation near the uplifts. The thickness of the Lower Cretaceous sediments increases in the northern, NW and NE flanks of the graben. Their maximum thickness is about 320 m. The BKL unconformity is the major cause of erosion of the Lower Cretaceous sediments along the southern, SE and SW flanks of the graben. In the Jora and Palmyra areas towards the NW flank of the Euphrates graben, the Upper Triassic and Lower Cretaceous sediments show no changes in thickness. In these areas, there was more space for sediment accumulation, and the sediments were less influenced by the BKL and BKU unconformities and thus less eroded.

1. Alsouki M., Taifour R., 2015. The Tectono-Depositional Evolution of the Syrian Euphrates Graben Area Using the 3D Seismic Data. Arabian Journal of Geosciences 8, 7577–7587. https://doi.org/10.1007/s12517-014-1692-4.

2. Barazangi M., Seber D., Chaimov T., Best J., Litak R., Al-Saad D., Sawaf T., 1993. Tectonic Evolution of the Northern Arabian Plate in Western Syria. In: E. Boschi, E. Mantovani, A. Morelli (Eds), Recent Evolution and Seismicity of the Mediterranean Region. Kluwer Academic Publishers 402, 117–140. https://doi.org/10.1007/978-94-011-2016-6_5.

3. Best J., 1991. Crustal Evolution of the Northern Arabian Platform beneath the Syrian Arab Republic. PhD Thesis. Cornell University, 156 p. https://ecommons.cornell.edu/handle/1813/5536.

4. Best J., Barazangi M., Al-Saad D., Sawaf T., Gebran A., 1993. Continental Margin Evolution of the Northern Arabian Platform in Syria. American Association of Petroleum Geologists Bulletin 77 (2), 173–193. https://doi.org/10.1306/BDFF8BBE-1718-11D7-8645000102C1865D.

5. Brew G.E., Barazangi M., Al-Maleh A.K., Sawaf T., 2001. Tectonic and Geologic Evolution of Syria. GeoArabia 6 (4), 573–616.

6. Brew G.E., Litak R.K., Barazangi M., Sawaf T., 1999. Tectonic Evolution of Northeast Syria: Regional Implications and Hydrocarbon Prospects. GeoArabia 4 (3), 289–318.

7. Brew G.E., Litak R.K., Seber D., Barazangi M., Sawaf T., Al-Imam A., 1997. Summary of the Geological Evolution of Syria through Geophysical Interpretation: Implications for Hydrocarbon Exploration. The Leading Edge 16 (10), 1361–1552. https://doi.org/10.1190/1.1437518.

8. Caron C., Mouty M., 2007. Key Elements to Clarify the 110 Million Year Hiatus in the Mesozoic of Eastern Syria. GeoArabia 12 (2), 15–36.

9. Laws E.D., Wilson M., 1997. Tectonics and Magmatism Associated with the Mesozoic Passive Continental Margin Development in the Middle East. Journal of the Geological Society 154 (3), 459–464. https://doi.org/10.1144/gsjgs.154.3.0459.

10. Litak R.K., Barazangi M., Beauchamp W., Seber D., Brew G., Sawaf T., Al-Youssef W., 1997. Mesozoic-Cenozoic Evolution of the Intraplate Euphrates Fault System, Syria: Implications for Regional Tectonics. Journal of the Geological Society 154 (4), 653–666. https://doi.org/10.1144/gsjgs.154.4.0653.

11. Litak R.K., Barazangi M., Brew G., Sawaf T., Al-Imam A., Al-Youssef W., 1998. Structure and Evolution of the Petroliferous Euphrates Graben System, Southeast Syria1. American Association of Petroleum Geologists Bulletin 82 (6), 1173–1190. https://doi.org/10.1306/1D9BCA2F-172D-11D7-8645000102C1865D.

12. Mouty M., Gout C., 2010. Overview of the Triassic System in Syria: Lithostratigraphic and Biostratigraphic Correlations with Neighboring Areas. GeoArabia 15 (1), 95–114.

13. Sadooni F.N., Alsharhan A.S., 2004. Stratigraphy, Lithofacies Distribution, and Petroleum Potential of the Triassic Strata of the Northern Arabian Plate. American Association of Petroleum Geologists Bulletin 88 (4), 515–538. https://doi.org/10.1306/12030303067.

14. Sharland P.R., Casey D.M., Davies R.B., Simmons M.D., Sutcliffe O.E., 2004. Arabian Plate Sequence Stratigraphy – Revisions to SP2. GeoArabia 9 (1), 199–214.

15. Yousef I.M., Morozov V.P., 2017a. Characteristics of Upper Triasic Sandstone Reservoirs in Syria Using Analysis of Laboratory Methods. Georesursy 19 (4), 356–363. https://doi.org/10.18599/grs.19.4.8.

16. Yousef I.M., Morozov V.P., 2017b. Structural and Mineralogical Characteristics of the Clay Minerals in Upper Triassic Sandstone Reservoir, Euphrates Graben, East Syria. Neftyanoe Khozyaystvo – Oil Industry 8, 68–71. https://doi.org/10.24887/0028-2448-2017-8-68-71.

17. Yousef I., Morozov V., El Kadi M., 2016. Sedimentological Review of Upper Triassic (Mulussa F Formation) in Euphrates Graben, Syria. Journal of Engineering and Applied Sciences 11 (14), 3067–3079.

18. Yousef I., Morozov V.P., El Kadi M., 2020. Influence and Control of Post-Sedimentation Changes on Sandstone Reservoirs Quality, Example, Upper Triassic (Mulussa F Reservoir), and Lower Cretaceous (Rutbah Reservoir), Euphrates Graben, Syria. Russian Journal of Earth Sciences 20, ES2007. https://doi.org/10.2205/2020ES000706.

19. Yousef I., Shipaeva M., Morozov V., Mohammad E.K., Abdullah A., 2019. Lithofacies Analysis and Depositional Environments of the Upper Triassic and Lower Cretaceous Sediments in Euphrates Graben, Syria. In: Surveying Geology and Mining Ecology Management SGEM 2019. Proceedings of the 19th International Multidisciplinary Scientific Geoсonference (June 30 – July 6, 2019). Vol. 19. Iss. 1.1. Sofia, p. 279–286. https://doi.org/10.5593/sgem2019/1.1/S01.034.

20. Yousef I., Sudakov V., Morozov V., Mohammad E.K., 2018. Diagenetic Clay Minerals and Reservoir Quality of the Upper Triassic Sandstone in Euphrates Graben, East Syria. In: Surveying Geology and Mining Ecology Management SGEM 2018. Proceedings of the 18th International Multidisciplinary Scientific GeoConference (July 02–08, 2018). Vol. 18. Iss. 1.4. Sofia, p. 397–404.

21. Yousef I.M., Usmanov S.A., Morozov V.P., Validov M.F., 2017. Diagenetic Chlorite, Illite and Illite-Smectite Minerals in Sandstone Reservoir; Structure, Morphology and Precipitation of Upper Triassic Reservoir, Syria. In: Surveying Geology and Mining Ecology Management SGEM 2017. Proceedings of the 17th International Multidisciplinary Scientific Geoсonference (November 27–29, 2017). Vol. 17. Iss. 1.5. Vienna, p. 115–124. https://doi.org/10.5593/sgem2017H/15/S06.015.

22. Ziegler M., 2001. Late Permian to Holocene Paleofacies Evolution of the Arabian Plate and its Hydrocarbon Occurrences. GeoArabia 6 (3), 445–504.