Sedimentation, depositional environments, and hydrocarbon potential of the Maastrichtian-Paleocene Araromi Formation, eastern Dahomey (Benin) Basin, southwestern Nigeria

• Published in: Journal of petroleum exploration and production technology 2021-11, Vol.11 (11), p.3917-3934
• Main Authors: Oluwajana, Oladotun Afolabi, Opatola, Abraham Olatunji, Adamolekun, Olajide Jonathan, Ndukwe, Otobong Sunday, Olawuyi, Gabriel Toluwalope, Ofiwe, Collins Uche, Bolaji, Taiwo Ayodele, Adebambo, Bamidele Adeniyi, Oluwajana, Oladipo Omoniyi
• Format: Article
• Language: English
• Subjects: Bitumens; Brackish water; Coastal waters; Cores; Cretaceous; Earth and Environmental Science; Earth Sciences; Energy Systems; Geochemistry; Geology; Hydrocarbons; Industrial and Production Engineering; Industrial Chemistry/Chemical Engineering; Limestone; Lithofacies; Monitoring/Environmental Analysis; Offshore Engineering; Oil and gas exploration; Oil exploration; Organic carbon; Organic matter; Original Paper-Exploration Geology; Palaeocene; Paleocene; Palynology; Petroleum; Rocks; Sandstone; Sedimentary environments; Sedimentary rocks; Sedimentation; Sedimentation & deposition; Sedimentology; Sediments; Shale; Shales; Shelves; Siltstone; Storms; Total organic carbon; Wind effects
• ISSN: 2190-0558; 2190-0566
• DOI: 10.1007/s13202-021-01262-7

The Cretaceous sediments in southwestern Nigeria are host to one of the largest bitumen deposits in the world. In the current paper, an integrated study on sedimentology, palynology, and applied petroleum geochemistry of the Maastrichtian-Paleocene Araromi Formation was used to determine the depositional environments and hydrocarbon potentials of the formation on the eastern Dahomey Basin. Four sedimentary lithofacies were identified from core samples, namely, lower limestone (F 1 ); medium to coarse-grained sandstone (F 2 ); lower loosely consolidated sandstone (F 3 ); and shale and siltstone (F 4 ). Sedimentation in the eastern Dahomey Basin occurred mainly in fluvial and shallow-marine (shelf) environments. The palynological assemblages of the Araromi Formation reflect deposition in coastal through brackish water to shallow shelf environment with periods of localized wind-induced storms. The shale and siltstone samples of the Araromi Formation are characterized by total organic carbon (TOC) values of up to 2.50 wt % and S 2 (hydrocarbon-generating potential) values ranging from 0.26 to 0.70 mgHC/g rock, indicating poor source rocks. Shales show poor quality and thermally immature organic matter at shallow depth and could neither have generated liquid hydrocarbon nor contributed to the heavy oil occurrence on the bitumen and tar-sand belt of eastern Dahomey (Benin) Basin.