Abstract: The Use of Age Related Biomarkers in Oils from Southern Brazilian and West African Marginal Basins

Brooks, P. W.; Mello, M. R.; Barbanti, S. M. - Petrobras/Cenpes; Moldowan, J. M. - Stanford University

Age related biomarkers are, as the name implies, biomarkers whose appearance in oils and source rock extracts are restricted to certain geological time periods. Thus, their presence in oils and source rock extracts can be of use to constrain, within limits, the age of the oil or source rocks.

Determination of the distributions of the age related biomarkers can only be achieved using sophisticated gas chromatography — mass spectrometry — mass spectrometry (GC-MS-MS) techniques.

The use of the specific biomarkers such as C₂₆ steranes, bicadinanes, oleananes, 2 and 3-methyl steranes, dinosterane type steroids and diterpenoid molecules have allowed geochemists to not only distinguish different origins related to specific organic facies for oils within one particular basin but to also determine the approximate age of each organic facies. This is of extreme importance when determining the petroleum systems that are active in each basin and of course has profound impact on exploration strategies.

The application of this methodology allows the characterization and differentiation among groups of oils involving the Southern Brazilian and West African marginal basins, although other geochemical, stratigraphic and geophysical data have revealed similarities among their petroleum systems.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil