Source Rock Kinetics and Organic Petrology of the Gombe Formation, Gongola Basin Nigeria: Implication for Hydrocarbon Potential.

The interbedded coals and shales facies of the Gombe Formation were subjected to organic petrology and source rock kinetics for evaluation of thermal maturity, kerogen type and the hydrocarbon generation from the kerogen. The distribution and kinetic parameters obtained through kerogen cracking was generated by processing the data obtained from Rock eval 6 pyrolysis using ORFA (One Run Fixed A) software. The activation energy distributions observed in the samples are broad (41-65 kcal/mol) with associated fixed frequency factors of 2.00E+14/s indicating heterogeneous compositions and bond types typical of Type III kerogen (HI = 57-172 mgHC/gTOC). The peak hydrocarbon bond breaking is between 54 and 55 kcal/mol for the organofacies defining up to 70% of the petroleum potential while the main phase and peak of hydrocarbon generation is between 460 - 465oC for the organofacies at constant heating rate of 25oC/min. Petrographic examinations revealed that organic matter in the organofacies consists of opaque to non-opaque biostructured phytoclasts, cuticles and some common spores and pollen. Vitrinitic maceral was abundant in the samples indicating gas prone organic debris. Palynofacies revealed the presence of trilete spore and pollen well preserved in the samples and showed good fluorescence. The Thermal Alteration Index (TAI) ranges from 2.4-2.6 suggesting late diagenetic stage for the organic matter maturation. It is concluded that the samples are thermally immature and constitute moderate to good quantity of organic matter with potential to generate mainly gaseous hydrocarbon. [ABSTRACT FROM AUTHOR]