Biomarker Geochemistry of Oils extracted from the Campanian Lokoja Sandstone around Lokoja area, Southern Bida Basin, sheet 247 NW.

Abstract

Biomarkers geochemical analysis of Lokoja Sandstone was carried out around 
Lokoja of southern in the Southern Bida Basin with the sole aim to increase our 
understanding paleo-depositional environment, thermal maturity, qualities of the 
organic matter source. The method adopted involved field studies where careful 
observations and sampling of in-situ rocks at different stratigraphic units was done 
and then followed by laboratory method of organic geochemical analysis was 
conducted on the selected samples for the Biormarkers analysis using gas 
chromatography-mass spectrometry (GC-MS) analytical techniques. Laboratory 
analysis extracted the oil constituent from the Lokoja sandstone for which fractions 
of saturate, aromatics, resin and asphaltenes were obtained. The saturates 
fractions was further analyzed for identifications of m/z 185 n-alkanes, m/z 191 
terpanes for Ts,Tm and mz/ 217 steranes (Regular C27, C28 and C29) respectively, 
m/z 185 Pr/Ph ratios was 0.89 and 0.85 for LKJ 2 and LKJ 3 respectively while LKJ 1 
is typical of heavily  biodegraded is not readable. Ts/Tm ratios of the analzed 
samples ranges from 0.9-1.26 conforming to oils generated within early oil window 
Generally, it is suggested that the probable organic matter that generated the oil 
was deposited under the influences of sub oxic environmental condition and with 
integration of Ternary plot of C27, C28, and C29 regular of steranes  infers that the 
source rock of extracted oil in LKJ 3 is was possibly deposited in a continental setting, 
while LKJ 1 and 2 were deposited in a marine setting, thus, this can be generalized 
as mixed Organic source rocks that has thermally matured within the early oil 
window which is the onset of oil generation as confirm from Trisnorhopane thermal 
maturity (Ts/Tm) scale alongside Vitrinite reflectance scale.