Abstract

Oils extracted from limestones and sandstones of the Yolde Formation were analyzed using the gas chromatography mass spectrometry (GC-MS) to increase our understanding on it origin, thermal maturities and quality. Results obtained shows that the studied oils are all related and believed to have been sourced from a common petroleum source rock within the studied basin. Total ion current (TIC) of the studied oils shows presence of unresolved complex mixture (UCM) consistent with oils that have undergone biodegradation. This is not surprising as all the studied oils were extracted from outcrops samples. Trisnorhopanes thermal indicator of the studied oils varies between 1.2 to 1.6 which is equivalent to vitrinite relectance 0.88 to 1 consistent with oils sourced from source rocks within the oil window. The Yolde Formation is known to have a maximum burial depth beyond 2000 m in some part of the Northern Benue Trough. This is therefore expected to find non degraded oils associated with the deeply buried Yolde Formation

Key words: Northern Benue Trough, biomarker, oil geochemistry, trisnorhopane thermal indicator, biodegradation, Yolde Formation