--> Lithofacies, Biostratigraphy, and Sequence Stratigraphic Characterization of #4 Well, Greater Ughelli Depobelt, Niger Delta Basin, Nigeria: Implications for Hydrocarbon Exploration.

2018 AAPG International Conference and Exhibition

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Lithofacies, Biostratigraphy, and Sequence Stratigraphic Characterization of #4 Well, Greater Ughelli Depobelt, Niger Delta Basin, Nigeria: Implications for Hydrocarbon Exploration.

Abstract

Sedimentological, foraminifera and palynological investigations were carried out on fifty six (56) side wall core samples from #4 Well in Greater Ughelli Depobelt, Niger Delta Basin with the depth range from 6172 – 8854ft (1881 – 2699m). An attempt was made to determine the depositional environment, relative age and establish sequence stratigraphic framework of the strata penetrated by the well. The sedimentological analysis involves studying the samples under microscope and visually to describe their textures. Foraminifera preparation involves sample disaggregation and washing, drying and picking. Palynological preparation involves treating the samples with acids, mounting, identification and counting. The sedimenmtological analysis has led to the establishment of thirty eight (38) Lithozones and ten (10) Lithofacies units comprising of sand, silt, shale, sandy silt, shaly sand, shaly silt, silty shale, silty sand and coal/lignite. Foraminifera recovered are calcareous and arenaceous benthic foraminifera while planktic foraminifera are generally absent. Species recorded include Ammonia beccarii, Bolivina beyrichi and Bolivina cf. dertonensis. A total number of 586 palynomorphs were identified with the Praedapollis africanus, Peregrinipollis nigericus, Retibrevitricolporites obodoensis and Retibrevitricolporites protrudens as the diagnostic species. The alternation of shale, silt and sand revealed that the studied interval belongs to paralic Agbada Formation of the Niger Delta Basin. Foraminifera result revealed that the studied interval was deposited during Early Miocene Epoch of estimated numerical age of 19.4 – 22.0Ma corresponding to N5 – N4 planktic zone. While the palynological analysis depicted Oligocene to Early Miocene Epoch of estimated numerical age of 22.2 – 31.3Ma corresponding to P620/P580 and P560 Pollen Zonation. Five (5) maximum flooding surfaces and four (4) sequence boundaries were established within P620/P580 and P560 Pollen Zonation with Bolivina 26 (23.2Ma), Alabamina 1 (26.2Ma), Bolivina 27 (28.1Ma) and Uvigerinella 5 (31.3Ma) as the regional marker shale, thus, indicated Greater Ughelli Depobelt. The sediments penetrated by the well were suggested to be deposited within continental, through marginal marine and shallow marine environments. Hence, the alternation of sands and shales in the studied sections provides a union of source, reservoir and seal rocks that are essential for hydrocarbon accumulation and stratigraphic trapping.