Hydrocarbon-Source Correlation in the Obayied Sub-Basin, North Western Desert, Egypt: Controls on Generation of Natural Gas and Light Crude Hydrocarbon Blends

Hassan M. Leila M.L. Ahmed M. Issa G. Šegvić B. Hegab O.
December 2024 China University of Geosciences

Journal of Earth Science
2024 #35 Issue 6 1944 - 1965 pp.

Obayied sub-basin provides one-third of the annual natural gas production in the Egyptian Western Desert. The origin of the Obayied hydrocarbons are however poorly constrained. In this study, the molecular biomarkers of the Obayied hydrocarbon blend were studied to infer on their origin and generation mechanism. The API values are in the range of (41.3°–53.7°) reflecting post-mature hydrocarbons. The molecular biomarkers suggest a generation of Obayied crude from clay-rich fluvio-deltaic source rocks. Age- and maturity-relevant biomarkers (e. g., Ts/Tm trisnorhopanes and methylphenanthrene indices) reflect a successive expulsion of the Obayied crudes from mature Jurassic rocks (>1%Ro). Biological markers correlate perfectly with those of the Jurassic Khatatba shale and coal extracts attesting. Additionally, the Obayied gases are wet, thermogenic and have been derived from a mature type III kerogen (1.3%Ro–2%Ro). The studied gases display compositional characteristics of mixed coal- and oil-type gases, and were therefore derived via primary cracking of the Khatatba coal as well as secondary cracking of the light liquid crudes. The present study clarifies the controls on the geochemical processes responsible for the accumulation of liquid and gas hydrocarbon mix in the deep as well as shallow inverted rift basins of the north Western Desert, Egypt.

Egypt , hydrocarbons , Jurassic , kerogen , Khatatba , molecular biomarkers , natural gas , Western Desert

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Geology Department, Faculty of Science, Mansoura University, Mansoura, Egypt
School of Mining and Geosciences, Nazarbayev University, Astana, Kazakhstan
Department of Geosciences, Texas Tech University, Lubbock, 79409, TX, United States

Geology Department
School of Mining and Geosciences
Department of Geosciences

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