Abstract

The Cretaceous Bima formation is the oldest and thickest formation within the Benue Trough chiefly made up of sandstone with continental origin. In this study the studied section shows oil infilling pore spaces within the sands as reported by Bata, 2015 which further buttress the interest on the reservoir capability of the Cretaceous Bima Formation within the Northern Benue Trough. In the field observation three main section were studied and observed which are the dark grey section (indicating oil charged sands), the reddish brown section (non – oil charged) and the section that has been altered by orogenic events. These sands show minor bioturbation with planar gradational bedding as observed in the field, with a coarsening upward lithostratigraphic sequence typical of fluvial condition (figure 6 and 7) the studied section of the Cretaceous Bima sandstones having estimated average porosity of 5.50% having 11.80% as the highest and 0.66% as the lowest. Scanning Electron Microscope (SEM) photomicrographs and thin section photomicrograph of the studied sandstones belonging to Cretaceous Bima Formation show that the sandstones are fine to medium grain with grain size ranging from 0.1mm – 1.0mm, moderately to poorly sorted, sub-arkoses and lithic sub-arkoses (figure 8). Silica occurs as the main cementing agent in the studied sandstones (figure 9). The boundaries between the silica overgrowth and the detrital grains are mostly poorly defined.

Key words: Northern Benue Trough, Cretaceous Bima Formation, reservoir capability, oil charged, paragenetic sequence, porosity, silica overgrowth