An earlier study of GC-MS analysis on bitumen samples from the Agbabu area in Western Niger Delta showed the significant presence of gammacerane and no Oleanane and is suggested to be generated from the Lower Cretaceous (Neocomian) source rock, however, twelve core samples were obtained from the geological survey of Nigeria for both optical geochemical and biomarker analysis, two of the samples from Isan-9 well indicated the presence of Botryococcus braunii a freshwater alga which is characteristic of a lacustrine lake type environment. The extracts from the same core showed m/z = 191 chromatogram with the significant presence of gammacerane which is diagnostic for stratified water columns and characterizes a typical lake environment. However, the m/z = 191 chromatogram also shows the presence of Oleanane which is diagnostic for vascular plant materials, this doesn’t corroborate with that of the Ise-2 well. The Isan-9 well source rock is suggested to have occurred due to the evolving structural geology of the continental shelf after the onset of the rifting, whereby the dominant lake-type environment in the Early Cretaceous was accompanied by a sediment fill of continental runoffs containing vascular plant materials. This implies that an ancient lacustrine lake system was gradually modified as a result of sedimentary infill. And that the bitumen is sourced from the lower Cretaceous Neocomian source rocks.
References
[1]
Tyson, R.V. (1995) Sedimentary Organic Matter, Organic Facies and Palynofacies. Hapman and Hall, London, 615. https://doi.org/10.1007/978-94-011-0739-6
[2]
Adegoke, O.S., Oyebamiji, A.S., Edet, J.J., Osterloff, P.L. and Ulu, O.K. (2017) Geology of the Niger Delta Basin. In: Adegoke, O.S., Oyebamiji, A.S., Edet, J.J., Osterloff, P.L. and Ulu, O.K., Eds., Cenozoic Foraminifera and Calcareous Nannofossil Biostratigraphy of the Niger Delta. Elsevier, Amsterdam.
[3]
Whiteman, A.J. (1982) Nigeria: Its Petroleum Geology, Resources and Potentials. Graham and Trotman, London. https://doi.org/10.1007/978-94-009-7361-9
[4]
Lawrence, S.R., Munday, S. and Bray, R. (2002) Regional Geology and Geophysics of the Eastern Gulf of Guinea (Niger Delta to Rio Muni). The Leading Edge, 21, 1112-1117. https://doi.org/10.1190/1.1523752
[5]
Killops, S. and Killops, V. (2005) Introduction to Organic Geochemistry. 2nd Edition. Blackwell Publishing, Oxford. https://doi.org/10.1002/9781118697214
[6]
Mello, M.R. and Katz, B.J. (2000) Petroleum Systems of South Atlantic Margins. AAPG Memoir, 73, 273-231. https://doi.org/10.1306/M73705
[7]
Ola, P., Solomon, O. and Olabode, S.O. (2019) Regional Chronostratigraphic Framework of Sediments Build Up in the Benin Basin: A Guide for Hydrocarbon Prospecting. Environmental Earth Sciences, 78, Article No. 638.
https://doi.org/10.1007/s12665-019-8629-x
[8]
Haack, R.C., Sundararaman, P., Diedjomahor, J.O., Xiao, H., Gant, N.J., May, E.D. and Kelsch, K. (2000) Niger Delta Petroleum Systems, Nigeria. Petroleum Systems of South Atlantic Margins, 73, 213-231. https://doi.org/10.1306/M73705C16
