Diagenetic history and reservoir capability of Bima Formation, Northern Benue Trough, Nigeria

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, which fur-
ther 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 oro-
genic events. These sands show minor bioturbation with planar gradational bedding as
observed in the field, with a coarsening upward lithostratigraphic sequence typical of flu-
vial condition 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 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 0.1 to 1.0 mm, moderately to poorly sorted,
sub-arkoses, and lithic sub-arkoses. Silica occurs as the main cementing agent in the stud-
ied sandstones. The boundaries between the silica overgrowth and the detrital grains are
mostly poorly defined.