234 D32. Relevant Topics in Geochemistry (Posters)

Wednesday, 18 October 2023
8:00 AM - 5:30 PM
Hall B

PALEOENVIRONMENTS AND HYDROCARBON POTENTIAL OF THE BENDE AMEKI GROUP EXPOSED IN OGBUNIKE AREA SOUTHEASTERN NIGERIA

Paper number: 234-16
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

Eocene Sediments of the Bende-Ameki Formation in the Anambra Basin is the outcropping equivalent of the subsurface Agbada Formation in the Prolific Oil and Gas producing Niger Delta. The current study investigated the sedimentological, foraminfera asemblages, inorganic and organic geochemical charateristics from the outcrop samples of the Bende-Ameki Formation to determine the depostional environment and hydrocarbon potential. logging, section measurement, description and collection of representative samples were carried out in Ogbunike quarry site for laboratory analysis.

Sedimentological analysis shows that the sandstones are medium grained, moderate to poorly sorted, leptokurtic to platykurtic and nearly symmentrical to fine skewed with cross beddings. These reflecting a fluviallly influenced shallow marine environment.

Trace elements and their elemental ratios permit the interpretation of the paleoredox condition of the shales. V/V+Ni,V/Cr, V/Ni, and a plot of U/Th suggest an oxic terrestrial environment.

Benthic foraminifera assemblages in the shales consist of agglutinated species of Ammobaculites, Ammotium, Reophax and Lenticulina suggesting dysoxic to suboxic environment. Diversity is consistently low which are peculiar to harsh shallow marine environmental conditions.

Leco analysis and Rock-eval analysis of twenty shales samples indicates a TOC range from 0.39-8.81wt% averaging 2.32 wt%. Petroleum Source potential (S1+S2) of the shales ranges from 0.22-27.35kgHC/ton of rock with a mean value of 2.8kgHC/ton of rock whereas Hydrogen index values range from 26 to 292mgHC/gTOC with a mean of 67.3mgHC/gTOC. Tmax values for the pyrolysed shales range from 401°C- 424°C with a mean value of 410°C. The results suggest that the shales were deposited in an oxic paleoenvironment with good to moderate source rock potential to generate hydrocarbon with a predominance of gas prone Type III kerogen which are immature. These conditions have implication for the Agbada Formation as a source rock in the subsurface

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-388622

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