Paleoenvironmental reconstruction and hydrocarbon potentials of Upper Cretaceous sediments in the Anambra Basin, southeastern Nigeria

Adebayo, Olajide Femi and Adegoke, Adebanji Kayode and Mustapha, Khairul Azlan and Adeleye, Mutiu Adesina and Agbaji, Amos Okechukwu and Abidin, Nor Syazwani Zainal (2018) Paleoenvironmental reconstruction and hydrocarbon potentials of Upper Cretaceous sediments in the Anambra Basin, southeastern Nigeria. International Journal of Coal Geology, 192. pp. 56-72. ISSN 0166-5162

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Official URL: https://doi.org/10.1016/j.coal.2018.04.007

Abstract

Palynological, organic petrographic, and organic geochemical analyses of the Campanian-Maastrichtian sediments in Akukwa-2 well were carried out to infer their paleoenvironments, origin of the organic matter, and hydrocarbon generation potentials. The TOC values of the analysed sediments range from 0.27–3.02 wt%, while the S2 pyrolysis yield range from 0.55 to 3.35 mg HC/g rock. This indicates that the Nkporo and Mamu sediments possess fair source generative potential. The samples contain Type III-II and Type III kerogen as shown by the present-day HI values between 58 and 292 mg HC/g TOC and pyrolysis-GC data. The organic matter within the sediments is also likely to generate mainly gas. This is in agreement with the petrographic observations, which revealed that the analysed shale samples contain abundant vitrinite macerals, apart from bituminite, alginite, cutinite, and resinite. Also, the sediments are immature to early mature in terms of hydrocarbon generation as indicated by vitrinite reflectance, biomarker maturity, and pyrolysis Tmax data. Biomarker distribution ratios, palynomorphs assemblage, and organic petrographic observations further point out that the organic materials within the sediments were of mixed aquatic and terrigenous origin and were deposited under suboxic paleodepositional conditions. Based on sedimentological, palynological, and biomarker characteristics, the environment of deposition of the analysed sediments was inferred to be a relatively quiet, shallow marine with fluvial incursion, most especially at the upper part of the intervals studied and consequently, it is a delta associated depositional environment with a fluviatile influence. The sediments are therefore suggested to be deposited in a paleogeographic setting close to vegetation source.

Item Type: Article
Uncontrolled Keywords: Palynology; Biomarker distribution; Organic matter; Source rocks; Suboxic
Subjects: Q Science > Q Science (General)
Q Science > QE Geology
Divisions: Faculty of Science > Dept of Geology
Depositing User: Ms. Juhaida Abd Rahim
Date Deposited: 08 Oct 2019 03:41
Last Modified: 08 Oct 2019 03:41
URI: http://eprints.um.edu.my/id/eprint/22703

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