Provenance, Paleoclimate, Paleoenvironment and Kerogen Characterization of the Paleocene Imo Formation from Owan-1 Well: Insights from Geochemistry and Mineralogy
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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 2 2 3 enriched in SiO , Al O and Fe O compared to CaO, MgO, K O, MnO, TiO , and P O . The Average concentration of 2 3 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 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, -1 illite, biotite and carbonates. The spectra in the samples revealed bands within 1111cm , 1102cm and 1033cm -1-1 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.
Publication Info:
Author: Jimoh, A.Y. , Ojo, O.J. , Haruna, K.A. and Mariam, B.
Volume: 60
Issue: March
Published By: Nigerian Mining and Geosciences Society (NMGS), 2024-03-01