Use of trace metals to identify Illinois crude oils

The purpose of this study was to analyze the trace metal constituents of Illinois crude oils and determine if their range in concentration might provide a means of identifying the oils. Samples of crude oils were obtained from eightfields and trace metals were analyzed by spectrochemical methods. Essentially uniform concentration of vanadium and nickel were found within a single oil reservoir, whether the samples were collected from different wells or at different times from the same well. The trace concentration of vanadium and nickel ranged from 0.1 to 5 parts per million, and there was a marked reduction in their concentration as the geologic age of the oil producing zones increased from Pennsylvanian to Devonian. Thus, significant differences in the concentration of vanadium andnickel were obtained. The ratio of vanadium to nickel concentrations was about 0.4 to 0.5 for practically all samples and therefore could not be used for identification. A correlation of the trace copper concentration and a qualitative analysis of all trace elements also failed to provide a means of identification.