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Abstract: UV-Fluorescence Spectral Characteristics of Crude Oils and their Correlation with API Gravity, Source and Degraded Condition; Implications for Near Surface Geochemical Exploration and Hydrocarbon Well Logging Applications


Fluorescence spectra of crude oils from a USGS collection in Denver, Colorado, were analyzed by a synchronous scanned UV-fluorescence technique. The scanning method reveals several fluorescence emission bands that are characteristic of crude oils. The peak intensities of these emission bands are measured for a variety of oil types. Fluorescence scanning methods have improved in recent years to provide more detailed information than previous techniques.

Aromatic hydrocarbons in crude oils fluoresce at different wavelengths according to the number of aromatic rings present in the compound. Usually, larger aromatic molecules fluoresce at longer wavelengths. As a result, a relationship is observed between the API gravity of crude oil and the band peak of maximum fluorescence. A relationship is also shown between the ratios of different fluorescence band peak intensity in the spectrum of that oil. The effects of degraded oils and different source type are also shown.

The sensitivity of the method allows part per million quantities of oil to be detected in soil samples, providing an effective microseepage exploration tool. Drill cuttings from exploration wells have also been examined for oil content and character using the technique. Caveats for these applications are discussed.

AAPG Search and Discovery Article #90946©1997 AAPG Rocky Mountain Section Meeting, Denver, Colorado