Geology, geochemistry and biomarker evaluation of Lafia-Obi coal, Benue Trough, Nigeria

Lafia-Obi coals from four boreholes were investigated in this study to ascertain their sedimentological and geochemical characteristics. This data enables the proper evaluation of their oil source rock potential and industrial utilization. The Lafia-Obi area is underlain by rhythmic sequences of shale, sandstone and limestone with varying thicknesses of interbedded coal, inferring deposition under shallow marine conditions. The ash and moisture contents of the coal are high suggesting good potential for use in the steel industry. The relatively low volatiles and high vitrinite/inertinite contents indicate that the coal has an appreciable coking quality. Although the total organic carbon content exceeds the kerogen threshold of 0.5 wt% for generation of crude oil, the high vitrinite reflectance values (R0>1.0%) and several geochemical maturity indices indicate mature to overmature facies. The bitumen compositions also reflect full maturity. The geological and geochemical characteristics of the Lafia-Obi coals are compared and contrasted with those of Enugu coals, with emphasis on the possible economic applications of the former.