Akinmosin A. A, Omosanya K. O., Ikhane P. R, Mosuro G. O and Goodluck I
Bitumen represents an alternative energy source. They are found in boreholes and as seepages in south western Nigeria. Geophysical survey and sedimentological analysis was carried out on the bitumen seepage at onikitibi (longitude: 04° 18' 18" E and latitude: 06° 39' 39" N) with a view to elucidate its electrical and lithological characteristic. Electrical resistivity profiling and one vertical electrical sounding along a profile of inter-electrode spacing of 5m-30m, and 1000m were carried out using the Wenner and Schlumberger electrode configuration along the seepage zone. Three samples collected from the exposure were subjected to granulometric analysis in order to determine their particle size distribution and textural characteristics. The samples are gravelly and muddy sandstones that are unimodal, coarsed skewed and poorly sorted. The three samples are mesokurtic and platykurtic. The provenance suggests a single source of sediment supply that is close to the study area which implies the sediments are texturally immature. The bitumen seepage has resistivity value of >4219Ωm on the 2D profile and it could not be detected with the Vertical Electrical Sounding (VES) method. Geometrically, the seepage extends ~14m (West to East) and 11m deep. The VES result imaged the Ise Formation which underlain the Afowo Formation in which the Bitumen is housed. The study established that the bitumen has high resistivity in contrast to previous values obtained in other parts of the basin. Therefore, bitumen in the basin has both low and high resistivity values.
