Geochemical characterization of FE-1 well, Onshore Western Niger Delta Basin, Nigeria

Abstract

Major oxides and trace elements analysis was carried out on ditch cutting samples of FE-1 well, Onshore, Niger Delta Basin, to define their oxygen condition, paleo-climatic conditions, provenance, tectonic setting, sandstone classification and maturity of the sediments. Sedimentological analysis revealed five main lithofacies comprising of sandstone, shaly sand, mudstone, sandy clay and sandy shale. Geochemical results indicates that the average value of silica (87.1 wt. %) is far higher than the average values of the rest oxides which shows the duration and intensity of weathering and destruction of other minerals during transportation. Bivariate plot of La/Sc versus Th/Co, Zr versus TiO₂, and trace elemental ratios of Th/Sc, Th/Co, Th/Cr, Cr/Th, La/Sc establishes that the source of the sediment are from felsic rock. Different chemical classification schemes characterized the sediments as quartzarenite, lithic arenites and Fe-rich sand. The plot of Log (K₂O/Na₂O) versus Log (SiO₂/Al₂O₃) and K₂O/Na₂O versus SiO₂ all plotted mainly in the passive margin zone. The low average value of uranium content, trace elemental ratios of U/Th, Ni/Co, Cu/Zn, V/Cr and binary plot of Ni/Co versus V/Cr indicated an oxic environment of deposition. However, the binary plot of Ni/Co versus V/ (V+Ni) indicates oxic to anoxic condition during deposition of the mixed marine and terrigenous source input sediment. Binary plot of SiO₂ versus (Al₂O₃+Na₂O+K₂O) designates deposition mainly in humid/semi-humid climatic condition. The samples studied have a much higher SiO₂/Al₂O₃ ratio with low Fe₂O₃/K₂O ratio, thus, they are mineralogically mature. The Al₂O₃/(CaO+MgO+Na₂O+K₂O) ratio inferred that there are stable mobile oxides in the samples.

Keywords: Major oxides, lithic arenites, provenance, tectonic setting.