Vanadium, Nickel, and Iron Trace Metals in Crude Oils of Western Canada

Abstract

Typical crude oils from western Canada produced from host rocks ranging in age from Upper Devonian to Upper Cretaceous were examined for the occurrence of vanadium, nickel, and iron trace metals. The concentrations of the metals, believed to have been closely associated with the oils since genesis, varied inversely with the A.P.I. gravity of the oils. The concentration of the three metals in the oils varies form 0.04 to about 600 parts per million. While some influence on the present trace-metal content of the oils is attributed to the starting materials of the oils and the availability of the oils at that time, the major effect seems to be one resulting from degradation and maturation of young petroleums. In general, the vanadium-containing organic molecule appears to be less stable than the nickel-containing molecule, resulting in a net lowering of the vanadium-to-nickel ratio of the oils as the apparent age becomes older. In detail, some of the trace-metal results appear to add to knowledge about the time and mode of migration and accumulation of crude oils in western Canada. Three groups of Devonian oils appear to exist, and two of these groups appear to describe the oils produced from the Cretaceous Viking sands of Alberta and western Saskatchewan and the Cretaceous Cardium sands of the Pembina field.