The gas and oil generation potential of organic matter of a source rock depends on the nature of the organic matter and its thermal history. The maceral composition is a direct measure of the original organic matter in immature rocks. The optical properties of specific maceral groups are used for the determination of their degree of maturation. Pyrolysis is a means for the evaluation of the generation potential. A combination of these methods enables a comparison of generation properties of different sources.

Kerogen concentrates were separated by heavy liquids into fractions

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enriched in a single maceral group (algae, altered algae, particulate liptinites, amorphous liptinites, amorphous humic matter, vitrinite, and inertinite). Their composition and maturation level were defined by transmitted light, fluorescence, and vitrinite reflectance. These measurements were repeated after pyrolysis.

The proportion of volatilized material ranges between 84 and 5% for algae and inertinite, respectively. The hydrocarbon yield ranges between 660 and 13 mg hydrocarbons/g organic matter for amorphous liptinites and inertinites, respectively. The residue after pyrolysis resembles inertinite ranging from micrinite to inertodetrinite except for vitrinites (and inertinites) which retain their textural characteristics. These types of inertinites occur in over-mature sequences. The yields obtained by pyrolysis may be used to estimate the relative potential of the different maceral types. They possibly represent maximal values.

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