Hydrocarbon generating potentials of benue trough coals

Abstract

Benue trough is an inland coal bearing basin that has been only lightly explored for petroleum. An organic geochemical analysis of coal samples from Kumo and Lamza in the upper part of the trough and from Lafia-Obi in the lower part was undertaken to assess their hydrocarbon generative potentials. The highest %Ro and Tmax of 0.9–1.1 % and 449–455 °C was found in Lafia-Obisamples, next was Lamza with 0.5–0.7 % and 434–438 °C and Kumo with 0.4–0.6 % and 415–429 °C. The HI of Lafia-Obi, Lamza and Kumo are within the ranges of 136–246 mg HC/g TOC, 184–269 mg HC/g TOC and 167–322 mg HC/g TOC respectively. The Odd-over-Even-Predominance (OEP) values and pristane/phytane (Pr/Ph) ratios of the samples suggest that they are dominantly terrestrial innature and were deposited in an oxic to suboxic environment. Ratios of 20S/(20S + 20R)ααC29 cholestanes, 20S/(20S +20R)ββC29 cholestanes, βα/(βα + αβ) C30 hopanes, Ts/Ts + Tm C27 hopanes and other maturity parameterssuggest that Lafia-Obi is highest in maturity (peak oil window), followed by Lamza (earlyoil window)and then Kumo (immature).