Provenance, Paleoclimate, Paleoenvironment and Kerogen Characterization of the Paleocene Imo Formation from Owan-1 Well: Insights from Geochemistry and Mineralogy

Abstract

The Paleocene shales of the Imo Formation, Niger Delta were investigated to reveal their organic and mineralogical composition, kerogen type, paleoweathering, provenance, paleoclimate, and paleoenvironments. Shale samples from Owan-1 well penetrating the Paleocene Imo Formation were analyzed by X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), and Fourier Transform Infra-red (FTIR) Spectroscopy. The results showed that the shales are enriched in SiO , Al O and Fe O compared to CaO, MgO, K O, MnO, TiO , and P O . The Average concentration of 2 2 3 2 3 2 2 2 5 SiO , Al O and Fe O are 25.5 wt.%, 9.65 wt.% and 5.46 wt.% respectively. Bivariate plots of the Chemical Index of 2 2 3 2 3 Alteration (CIA) vs Plagioclase Index of Alteration (PIA), and elemental ratio such as SiO /Al O indicate low to 2 2 3 moderate chemical weathering. The discriminant function diagram DF1 vs DF2, plots of TiO vs Al O , and TiO vs Zr 2 2 3 2 revealed intermediate igneous provenance. The plot of SiO vs (Al O +K O+Na O) indicates semi-humid to semi-arid 2 2 3 2 2 climatic conditions. The high Sr/Ba indicates diagenesis and high salinity stratification in the water column. The Sr/Ba value >1 (avg. 1.27) suggests mainly marine depositional environments and oxic conditions for the shales. The main minerals identified by XRD are quartz and kaolinite with minor concentration of montmorillonite, chlorite, illite, biotite and carbonates. The spectra in the samples revealed bands within 1111cm-1, 1102cm and 1033cm suggesting presence of quartz, kaolinite and illite. The FTIR spectra also showed presence of long chain aliphatic (saturated) compounds, unsaturated alkenyl C=C stretch, carbonyl C=O, hydroxyl compounds and aromatic phenolic group. The A and C factor from FTIR characterize the kerogen in the investigated shale samples as Type II with potential to generate oil and gas