Source of organic matter and paleoenvironment of deposition of crude oils from the Niger Delta Basin

Abstract

The study employed thirteen (13) crude oil samples from thirteen (13) producing wells, with the aim of examining the source of organic matter and the paleoenvironment of deposition. The crude oils were deasphaltened and the maltene fraction fractionated to obtain the saturates. The saturates were subjected to gas chromatography mass spectrometer (GCMS) analysis for the steranes, Isoprenoids and n-alkanes, and triterpanes and hopanes biomarker chromatograms. The biomarker composition of the studied oils indicates weakly oxic and reducing environmental conditions for the studied samples, consistent with marine deltaic environment of deposition. The study shows that the oils are associated with a mix of terrestrial and marine organic matter with a comparatively higher terrestrial and lower marine algae organic matter input. The oleanane index of 1.8 and the presence of oleanane in the studied samples denote higher terrigenous plant input into the source rock the generated the crude oils.