応用科学研究の進歩 オープンアクセス

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Geochemical effects of petroleum generation potential from basal campanian source rocks in the Anambra Basin, S. E. Nigeria

Uche M. Uzoegbu and Victor U. Ukaegbu and Hermann Wehner

Shale from basal Campanian strata of the Anambra Basin has been characterised by petrological and geochemical techniques. The aims of this study were to assess the quality of its organic matter, evaluate its thermal evolution and highlight its potential as a source rock. The total organic carbon (TOC) (2.55wt%) of the shale constitutes that of a good source rock with gas-prone kerogen indicated by Rock-Eval S2/S3 (2.19). The high oxygen index (OI) (19.09 mgCO2g-1TOC) and pr/ph (6.50) suggest deposition in a shallow marine environment. The n-alkane distribution dominated by n-C24 – n-C31 and infrared spectrum dominated by aliphatic and aromatic functional groups are considered to be indicators of Type III kerogen. The CPI (1.67), Tmax (430oC), C31(S/S+R) ratio (0.76) and Ro (0.56%) all indicate the onset maturity of this rock. This thermal evolution is thought to account for its current hydrogen index (41.20 mgHCg-1TOC). Generated petroleum may not have reached the threshold for hydrocarbon expulsion but a review of petroleum system elements in the basin will stimulate high prospects in the Anambra basin