Quantitative Microscopic Spectral Fluorescence Measurement of Crude Oil, Bitumen, Kerogen, and Coal
Prasanta K. Mukhopadhyay, Jurgen Rullkotter
Ten samples each of black shale (kerogen and bitumen fractions) from Lias epsilon, coal from Western Canada and nine crude oil and condensate samples from Alaska and northern Germany have been studied using quantitative microscopic spectral fluorescence. The parameters used are ^lgrmax, red/green quotient (Q), and alteration of fluorescence emission intensity under UV excitation.
In kerogen fractions, alginites from both black shale and coal show a shift of ^lgrmax toward the red spectrum from Ro of 0.5 to 1.5. Alteration is positive up to 0.7 Ro; thereafter, alteration is both positive and negative. Bitumen fractions from Lias epsilon show a red shift of ^lgrmax and increase of Q up to 0.7 Ro; thereafter, both ^lgrmax and Q change in the opposite direction. Alteration shows a similar trend. Seven crude oils shift their ^lgrmax from 600 to 430 nm and show decrease in Q-value with increasing maturation. All of them show high negative alteration. One heavy immature crude has a positive alteration and ^lgrmax of about 620 nm. One biodegraded crude did not show any shift of ^lg max and has low negative alteration.
Using the same parameters, the data show that kerogen and crude oil have opposite maturation trends. Autochthonous bitumens include both kerogen and crude oil characters. Immature, biodegraded, or normal crude oil of different maturity can be characterized using these parameters.
Quantitative spectral fluorescence microscopy yields more accurate maturation parameters for the Type I and II kerogens than vitrinite reflectance because the fluorescence of liptinites are used (i.e., the main oil-generating macerals). This method may become the most suitable inexpensive scanning technique for the characterization of crude oil, condensate, and autochthonous/allochthonous source rock bitumens.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.