Provenance, diagenesis and reservoir quality of the Aptian-Albian Bima sandstone, Upper Benue Trough, NE Nigeria

This study aimed to understand the reservoir potential of the Cretaceous Bima Sandstone in the Upper Benue Trough, Nigeria, by examining its petrographic and geochemical characteristics. Our goal was to ascertain its petrofacies, provenance, and tectonic setting, and critically assess how these fundamental geological attributes impact reservoir quality. An integrated approach combining detailed petrography, major and trace element geochemistry, and various weathering indices was systematically applied to the Upper and Lower Bima units. The results indicate that the Bima Sandstone comprises predominantly subarkose and quartz arenites, with some sublitharenite, and exhibits variable mineralogical maturity. Geochemical proxies such as SiO₂ (19.94–89.55), Zr (8.00 ppm–865.00 ppm), Chemical Index of Alteration (CIA, 19.00 to 97.00), and Index of Compositional Variability (ICV, 0.00 to 4.70) revealed provenance from highly weathered felsic igneous to mixed felsic-mafic sources, suggesting derivation from the continental crust under transitional to humid climates. Discrimination plots predominantly indicate a passive continental margin with a localized active continental margin influence. These geological characteristics, coupled with the depositional environment, influence the distribution and interconnectivity of porosity and permeability. The Upper Bima, with its high chemical maturity and intense weathering, shows better primary porosity (average 12.8), making it a promising hydrocarbon reservoir. Conversely, Lower Bima, with its varied provenance and lower maturity, shows higher heterogeneity and generally low porosity (average 5.5). The study has revealed the varied reservoir quality of the Bima Sandstone, which is essential for the strategic enhancement of hydrocarbon exploration and development in the Upper Benue Trough.