--> Abstract: Fluorescence Spectral and Geochemical Analyses of Kerogen, Organic Extracts and Crude Oils: A Petrographic Approach to Determination of the Onset of Oil Generation, by H. Zhiwen; #90987 (1993).

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ZHIWEN, HAN, Department of Geology, Southern Illinois University at Carbondale, Carbondale, IL

ABSTRACT: Fluorescence Spectral and Geochemical Analyses of Kerogen, Organic Extracts and Crude Oils: A Petrographic Approach to Determination of the Onset of Oil Generation

Fluorescence spectral and geochemical analyses were conducted on 16 Lower Tertiary well cuttings samples (2389-4162m from a single well) and 4 crude oils from the Jidong basin, one of the lacustrine rift basins in Eastern China. Brightly fluorescing Botryococcus-related alginites are rare but do occur in each sample. With increasing depth, their fluorescence spectra shift from lower to higher wavelengths. The maximum wavelength (lamda<max>), spectral quotient (Q) and color index (CIE<x>) steadily increase between 2389 and 3321 m, however, at around 3400 m the rate of these changes increases sharply. The spectral parameters of both the extracted aromatic and polar fractions also shift towards higher wavelengths with increasing depth. They, likewise, show a similar pattern o steady increase to 3400 m where there is a rapid increase or jump in the rate of change. This jump is especially clear in the spectra of the extracted aromatic fractions. The fluorescence jump of both the kerogen (alginite) and organic extracts at the depth of 3400 m also corresponds with dramatic chemical changes revealed by the GC/MS and pyrolysis-GC data, marking the onset of oil generation. At the depth of 3400 m the vitrinite reflectance (Rm) of the kerogen reaches 0.5% which also corresponds to the first coalification jump marking oil generation.

The geochemical data from both the oils and rocks confirm that all the four oil samples were generated from the black shale interval between 3870 and 4050 m. The fluorescence spectra of the aromatic fractions of the four oils shift towards higher wavelengths as the concentration of aromatics increases in the petroleum. In contrast, the spectra of the polar fractions are all similar, a phenomenon which might be exploited for oil-oil correlation.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.