Could the conventionally known Abu Roash “G” reservoir (upper Cenomanian) be a promising active hydrocarbon source in the extreme northwestern part of Egypt? Palynofacies,palaeoenvironmental, and organic geochemical answers |
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| Institution: | 1. Department of Geology, Faculty of Science, Cairo University, 12613, Giza, Egypt;2. Department of Geology, Faculty of Science, Assiut University, 71516, Assiut, Egypt;1. Geology Department, Faculty of Science, Zagazig University, Zagazig, Egypt;2. Botany Department, Faculty of Science, Zagazig University, Zagazig, Egypt;1. Ores and Mineralization Group, University of Leeds, School of Earth and Environment, Leeds, LS2 9JT, United Kingdom;2. ToroGold Limited, Piccadilly, St. James''s, London, W1J 9EJ, United Kingdom;1. Apache Exploration and Production Technology, USA;2. USA;3. Apache Egypt Company, USA;1. Department of Geology & Geophysics, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia;2. Dipartimento di Scienze della Terra, University di Bari “Aldo Moro”, Via Orabona 4, I-70125, Bari, Italy;1. Department of Geology, Faculty of Science, Mansoura University, 35516 Mansoura, Egypt;2. Halliburton, Neftex Exploration Insights, 97 Jubilee Avenue, Milton Park, Abingdon, OX14 4RW, United Kingdom;3. Senckenberg Research Institute and Natural History Museum, 60325 Frankfurt am Main, Germany;4. Institute of Geology and Geochemistry of Petroleum and Coal, Energy and Mineral Resources Group (EMR), RWTH Aachen University, 52056 Aachen, Germany |
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| Abstract: | In different areas of the Western Desert of Egypt, the Abu Roash “G” Member exhibits either a reservoir or source affinity. Thus, thirteen cutting samples covering the Abu Roash “G” Member were selected from the Nest-1A well at Matruh Basin to investigate its hydrocarbon source potential. Palynological age dating of the section that is calibrated with foraminifera and ostracodes enabled a proper identification of the “G” Member. Detailed analysis of the vertical distribution of particulate organic matter of this member shows two palynofacies types. PF-1 reflects an outer middle shelf depositional environment of prevailed reducing (suboxic-anoxic) conditions for the organic-rich shales of the lower “G” Member (samples 1–8). While, PF-2 reflects a minor regression that resulted in deposition of another organic-rich shales of the upper “G” Member (samples 9–13) in an inner middle shelf setting under the same prevailing reducing (suboxic-anoxic) conditions.Organic geochemical analysis reveals good to very good potential of the “G” Member as a hydrocarbon source rock (1.8–2.41, avg. 2.15 total organic content wt %). It also shows good to very good petroleum potential (PP: 4.8–11 , avg. 8 mg HC/g rock). Pyrolsis and palynofacies analyses show kerogen type II for the lower “G” Member (samples 1–8), which is characterized by high Hydrogen index (HI: 396 and 329 mg HC/g TOC at depths 1500 and 1560 m) and very high dominance of oil-prone material (amorphous organic matter “AOM”, marine palynomorphs, and sporomorphs) and very rare occurrence of gas-prone material (brown phytoclasts). The upper “G” Member (samples 9–13) shows kerogen type II-III, which is characterized by a lower HI value of 213 mg HC/g TOC at depth 1340 m and it contains fewer amounts of gas-prone material and relatively lower AOM and marine palynomorphs in comparison to the upper “G” Member. Maturation parameters Tmax (430–433 °C), production index (PI: 0.1 mg HC/g rock), and thermal alteration index (TAI: 2+) indicate the lower “G” Member has already entered the early oil-window kitchen, and it is expected to produce oil. The upper “G” Member is expected to produce only oil with no gas shows, because it is marginally mature (Tmax 426 °C, PI 0.2, TAI 2). The source potential index (SPI: 5.3 t HC/m2) of the “G” Member shows it as currently generating moderate quantities of oil in the area of Nest-1A well.Consequently, the organic-rich shales of the “G” Member are suggested here as a promising, active oil source rock in that extreme northwestern part of the Western Desert of Egypt. However, for commercial oil recovery from the Abu Roash “G” Member, it is highly recommended to explore the depocentre of Matruh Basin at about 150 km east the Nest-1A well. |
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| Keywords: | Palynofacies Palaeoenvironment Organic geochemistry Abu Roash “G” Hydrocarbon potential North Western Desert Egypt |
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