An Assessment of the Hydrocarbon Potential of the Gombe Formation, Upper Benue Trough, Northeastern Nigeria: Organic Geochemical Point of View

Abstract

Gombe Formation is a heterogeneous sequence within the Upper Benue Trough consisting principally of shales with sands, clays and intercalations of coal. It is over 600m thick maximally in some parts of the sub-basin and has been dated Maastritchian. Fifteen (15) core samples from three (3) boreholes (BA-7, BA-16 and BA-17) dug around the Maiganga Coal Mine have been studied geochemically using Rock-Eval 6 method with the principal aim of evaluating their potential as possible source rock for petroleum. The result of the Rock-Eval analysis for analysed core samples from these boreholes within Gombe Formation shows that the samples in boreholes BA-7 and BA-16 contain Type II while those from borehole BA-17 contain Type III kerogen and that the samples from borehole BA-7 and BA-16 have very good generative potential while those from borehole BA-17 have good to very good potential. This study also reveals that the analysed samples especially those from borehole BA-7 and BA-16 may constitute good source rocks if the burial depth is sufficient. The Rock-Eval Tmax data available for thermal maturity assessment of the samples suggest that the analysed samples from the three boreholes are thermally immature. This assessment is consistent with the immaturity status of their coeval Formations (Pindiga and Gongila Formations) in other part of the Benue Trough, suggesting that those contemporaneous Formations may be related in depth and or have experienced similar geothermal gradient. It is therefore recommended that the thermal maturity of the analysed samples from the three boreholes be re-evaluated by other thermal maturity indices such as vitrinite reflectance measurement and biomarker evaluation in order to further evaluate the maturity status of the Formation.