Paleoenvironments, Texture and Mineralogy of Sandstones of Bida Formation exposed at Doko and a quarry along Bida-Minna Road, Northern Bida Basin, North Central Nigeria: Implication on Reservoir Quality.

Abstract

Paleoenvironments, texture and mineralogy of sandstones belonging to the Campanian –
Maastrichtian Bida Formation exposed at Doko and Quarry along Bida-Minna road,
northern Bida Basin, northcentral Nigeria, were investigated through grain size,
petrographic studies and X-ray diffraction to deduce their preliminary reservoir properties.
Grain size statistical variables (average mean, standard deviation, skewness and kurtosis)
for Doko sandstones are 0.55 mm, 1.44 mm, -0.02 mm and 0.98 mm and Quarry sandstones
are 0.83 mm, 1.06 mm, 0.06 mm and 1.28 mm. Average quartz, feldspar and rock fragment
minerals in Doko and Quarry are 61 %, 29 % and 9.9 % and 69 %, 10 % and 21 %
respectively. Non-opaque heavy minerals which are generally less than the opaque include
zircon, tourmaline and rutile with lesser garnet, apatite and monazite. And the XRD shows
quartz, orthoclase, muscovite, kaolinite, vermiculite, albite, goethite, and garnet in order of
decreasing concentration. The sandstones are generally bioturbated, cross stratified, poorly
sorted, with dominance of medium to coarse grain texture. They possess angular to sub-
angular mineral grain shapes, except for the conglomeratic sandstones that consist of sub-
rounded to rounded pebble sizes. Mineral petrography reveals that the sandstones across the
study areas are sub-litharenite to arkosic sandstones with short history of transportation and
deposition by fluvial settings. Their texture and mineral composition being immature to sub
mature is not favourable for a reservoir or an aquifer because of high matrix that can block
the poor spaces and cementing materials that will enhance cementation at deeper depth. This
will drastically reduce their porosity and permeability quality. The sandstones of Bida
Formation deposited at Doko are the most preferable for hydrocarbon reservoir and aquifer
due to their better textural and mineralogical features compared to the ones at the quarry
along Bida-Minna Road, northern Bida Basin.