OLEANANE PARAMETER - VERIFICATION BY QUANTITATIVE STUDY OF THE BIOMARKER OCCURRENCE IN SEDIMENTS OF THE NIGER DELTA

The variation of the absolute concentration of oleananes in three selected sedimentary columns of the Tertiary Niger delta is paralleled by the corresponding oleanane parameter (OP) profile, thereby confirming that the latter can be utilized for estimating the relative contribution of terrigenous organic matter. It is shown that OP features a dynamic range, especially at the oil-generative window (OGW), and can precisely delimit the top of the OGW which, for the Niger delta, is shown to coincide approximately with the 80-degrees-C isotherm and R(o)% approximately 0.55. This study provides the first evidence of the inadequacy of vitrinite reflectance as a maturity parameter for type III kerogen. Furthermore, based on the new findings, an alternative model for oleanene-oleanane interconversions in the geosphere is proposed.