Characterization of insoluble organic matter of the Lokpanta oil shales Anambra Basin, by quantitative infrared spectroscopy

Abstract

Conventional infrared (IR) spectroscopy was used to get quantitative information on the structure of the isolated kerogen of the Lokpanta oil shales in the Anambra basin. The kerogen was extracted from six shale samples collected from different geographical locations in the basin. Only about 1 to 14% of the kerogen present in the fine – grained sedimentary rock extract was recovered from the sedimentary organic residue. Quantitative IR spectroscopy indicates that the kerogen structure consists of about 19% of aliphatic groups ( bands around 2920- 2900, 1450- 1420 cm^-1) ; 53% of C=C, C= O, COO^- groups (bands around 1610 –1600cm^-1) and 28% of aromatic groups (bands around 900 –560 cm^-1). These percentages indicate that these kerogens are relatively richer in oxygen bearing functional groups than aliphatic and aromatic groups. This suggest not only that the kerogens are of intermediate maturity but also that they likely correspond to type 11 series, are marine – derived, anoxic, capable of generating oil and gas and originated from the same parent materials. Variation in the intensity of IR bands shows that kerogens from Lokpanta –Lekwesi area are more mature relative to those from Ndeaboh – Awgu.


KEY WORDS: Infrared spectroscopy, kerogen, characterization, oil- shales, source –rock, insoluble organic matter, correlation, Lokpanta, Anambra basin.


Global Jnl of Pure and Applied Sciences Vol.10(4) 2004: 585-593