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<p>Forty-one ditch-cutting samples from the ERH-51 well in the coastal swamp-offshore depobelt of the Niger Delta Basin were analyzed using thin-section petrography and foraminiferal studies to establish the lithostratigraphy, depositional environment, sequence stratigraphy, and hydrocarbon potential. Petrography identified two lithofacies, hemipelagic shale (Hs) and argillaceous shale (As), correlated with the Upper Akata and Lower Agbada Formations. Foraminiferal analysis revealed sixty (60 species consisting of forty (40) calcareous species and nineteen (19) agglutinated forms, along with echinoid remains and ostracods., facilitating the identification of six biostratigraphic zones including the <i>Globigerina nepenthes/Marginulina costata</i> Zone (Early Pliocene, N20/21), <i>Globorotalia tumida/Cyclammina minima</i> Zone (Late Miocene, N18/N19–Upper N17), and <i>Globorotaloides stainforthi/Brizalina dilatata</i> Zone (Middle Miocene, N4-N8), and dating the interval from the Early Miocene to Early Pliocene (17.83–4.16&#xa0;Ma). Sequence stratigraphy delineated six depositional sequences (S1–S6), bounded by sequence boundaries and maximum flooding surfaces, reflecting transgressive–regressive cycles. The stacking patterns suggest a progradational trend, with lowstand system tracts (LSTs) indicating deepwater deposition, transgressive system tracts (TSTs) preserving organic-rich shales, and highstand system tracts (HSTs) marking deltaic progradation. The depositional environment evolved from deep marine (Upper Akata) to prodeltaic and shallow marine settings (Lower Agbada), transitioning from outer neritic to upper bathyal depths. Hydrocarbon potential is primarily associated with organic-rich transgressive shales, suggesting possible unconventional reservoirs or overpressured shale systems without reservoir-quality sands. This study refines the stratigraphic framework of the Niger Delta, providing insights into shale-rich depositional systems, organic matter accumulation, and hydrocarbon exploration in similar basins worldwide.</p>

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Foraminifera bio-sequence stratigraphy and hydrocarbon potential of shale-dominated successions in the coastal swamp-offshore depobelt, niger delta

  • 期刊论文

  • 发表日期：

    2025年4月17日

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  • Tope Shade Alege,
  • Goodness Eleojo Joseph

摘要

Forty-one ditch-cutting samples from the ERH-51 well in the coastal swamp-offshore depobelt of the Niger Delta Basin were analyzed using thin-section petrography and foraminiferal studies to establish the lithostratigraphy, depositional environment, sequence stratigraphy, and hydrocarbon potential. Petrography identified two lithofacies, hemipelagic shale (Hs) and argillaceous shale (As), correlated with the Upper Akata and Lower Agbada Formations. Foraminiferal analysis revealed sixty (60 species consisting of forty (40) calcareous species and nineteen (19) agglutinated forms, along with echinoid remains and ostracods., facilitating the identification of six biostratigraphic zones including the Globigerina nepenthes/Marginulina costata Zone (Early Pliocene, N20/21), Globorotalia tumida/Cyclammina minima Zone (Late Miocene, N18/N19–Upper N17), and Globorotaloides stainforthi/Brizalina dilatata Zone (Middle Miocene, N4-N8), and dating the interval from the Early Miocene to Early Pliocene (17.83–4.16 Ma). Sequence stratigraphy delineated six depositional sequences (S1–S6), bounded by sequence boundaries and maximum flooding surfaces, reflecting transgressive–regressive cycles. The stacking patterns suggest a progradational trend, with lowstand system tracts (LSTs) indicating deepwater deposition, transgressive system tracts (TSTs) preserving organic-rich shales, and highstand system tracts (HSTs) marking deltaic progradation. The depositional environment evolved from deep marine (Upper Akata) to prodeltaic and shallow marine settings (Lower Agbada), transitioning from outer neritic to upper bathyal depths. Hydrocarbon potential is primarily associated with organic-rich transgressive shales, suggesting possible unconventional reservoirs or overpressured shale systems without reservoir-quality sands. This study refines the stratigraphic framework of the Niger Delta, providing insights into shale-rich depositional systems, organic matter accumulation, and hydrocarbon exploration in similar basins worldwide.