Elemental Composition and Geochemistry of Heavy Oil in Parts of Eastern Dahomey Basin, Southwestern Nigeria

Abstract

Bituminous tar sand deposit of South-western Nigeria represents the product of in-reservoir transformation of convectional crude oil by microorganisms. The biotransformation of the heavy oil has led to the alteration of both the chemical and physical characteristics of this oil. The change in the chemical composition has posed a great problem to the refineries as feedstock tends to react with refineries components thereby destroying refining plant. Hence the commercial production of these resources has not been encouraged.

Based on this, 14 samples spread across the tar sand belt of the region were taken and subjected to laboratory analysis. Result shows an average elemental composition of Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus to be 80%, 8%, 4.5%, 4.1% and 3.9% respectively. This considerable high Nitrogen and Phosphorus content is due to biodegradation which occur in the trap due to untimely harvest of the oil and water washing effect.

Keywords: Bituminous Tar Sands, Biotransformation, Reservoir