Geochemical and Biostratigraphical Evaluation of Lokpanta Shale in Abakaliki Anticlinorium, Anambra Basin Province, Southeast Nigeria

Abstract

A geochemical and biostratigraphic method has been applied to explore the quality of organic matter, thermal evolution, potential hydrocarbon source and type of fossils of Lokpanta Shale from the Abakaliki Anticlinorium, Anambra Basin Province, Southeast Nigeria. Data obtained reveal that the total organic carbon (TOC) (2.18wt%) of the shale constitutes that of good to excellent source rock with gas-prone kerogen indicated by Rock-Eval S₂/S₃ (2.32). The low oxygen index (OI) (27.20 mgCO₂g^-1TOC) suggest deposition under low energy environments. The plots of HI against T_max classified the organic matter as Type III kerogen. The poor concentration of OM is thought to account for its current hydrogen index (31.47 mgHCg^-1TOC). The predominance of Type III kerogen in the Lokpanta shale suggests their potential to generate gas in the deeply buried sections. The T_max values from the pyrolysis of the shales of the Lokpanta ranges from 428 to 442^oC corresponding to maturity levels within the oil formation. The lamination of the sediments of the Lokpanta area with no burrows and the occurrence of dominantly planktonic foraminiferal assemblages also indicate a quiet water anoxic marine condition.