The petroleum system of the Tenere Basin: oil geochemistry from the SH-1 wildcat well in eastern Niger
B. Liu, G. Zhang, F. Mao, J. Liu, D. Cheng and M. Lü
Issue: Vol 23, No 4, November 2017 pp. 427 - 439
Info: Article, PDF ( 1.59Mb )
The SH-1 wildcat well, firstly encountering oil, proved the existence of a working petroleum system in the Tenere Basin, but the origin of oil and its generation history is not fully understood. In this regard, one crude oil and nine Upper Cretaceous source rock samples from the SH-1 wildcat well in the Tenere Basin were characterized by a variety of biomarker parameters and stable carbon isotopic composition. The oil from the Tenere Basin displays a low pristine/phytane (Pr/Ph) ratio, low C29/C30 and C35/C34 hopane ratios, low C22/C21 and high C24/C23 tricyclic terpane ratios, and high gammacerane index (gammacerane/C30 hopane), suggesting shale source rocks deposited under an anoxic and relatively high-salinity environment. Relatively high C29 sterane concentrations, a low value of the regular steranes/17α(H)-hopanes ratio and a canonical variable from stable carbon isotopic composition larger than 0.47 indicate that the oil is mainly derived from terrestrial higher plants. Both aromatic maturity parameters and sterane isomerization parameters suggest that the oil was generated from an early mature source rock. Correlation between oils from the Tenere Basin and those from the Termit Basin confirms that these oils belong to the same genetic family. The oil–source rock correlation suggests that the oil from the Tenere Basin originated from the Upper Cretaceous marine source rocks, and the Yogou Formation can be considered as effective source potential.