Integrated Elemental and Mineralogical Characterization of Petroleum System Sediments in the Central Niger Delta Basin

Abstract

This study presents an integrated elemental and mineralogical characterisation of petroleum-system sediments from Wells 13 and 14 in the Abua-Odual area of the central Niger Delta Basin, southern Nigeria, with an emphasis on sediment composition, provenance, reservoir quality, and basin evolution. Drill-cutting samples (6 samples from Well 13 and 8 samples from Well 14) collected from depths of 8,000–15,000 ft were investigated using inductively coupled plasma–optical emission spectrometry (ICP–OES) for major-element composition and X-ray diffraction (XRD) for mineralogical characterisation. The elemental results demonstrate considerable vertical variability in both wells. Well 13 is characterised by relatively elevated Fe and Ca concentrations, with Ca reaching 34,000 mg/kg at 11,000 ft, whereas Well 14 exhibits pronounced elemental variability and exceptional Na enrichment, reaching 57,000 mg/kg at 12,000 ft. Pearson correlation analysis reveals a strong positive relationship between Al and K in Well 13 (r = 0.93), suggesting their association with aluminosilicate mineral phases. Well 14 displays stronger positive relationships among Al, Mg, Ca, and K, indicating greater integration among the principal mineral-forming elements. Mineralogical analysis confirms quartz as the dominant phase in both wells, with abundances ranging from 50–88 wt% in Well 13 and 24–81 wt% in Well 14. Kaolinite, albite, orthoclase, and illite constitute subordinate mineral phases, with Well 14 exhibiting greater mineralogical variability. In Well 13, quartz shows a strong negative correlation with albite (r = −0.92), while a similar inverse quartz–albite relationship occurs in Well 14, indicating systematic changes between quartz-rich and feldspar-rich intervals. The integrated elemental and mineralogical characteristics indicate predominantly siliciclastic sedimentation accompanied by variations in sediment supply, mineralogical maturity, and post-depositional modification. Well 13 represents a comparatively quartz-rich and mineralogically mature succession, whereas Well 14 exhibits greater geochemical and mineralogical heterogeneity. The findings demonstrate the usefulness of integrated elemental and mineralogical datasets for understanding sediment provenance, reservoir heterogeneity, and petroleum-system evolution in the central Niger Delta Basin.