APPLICATION OF AROMATIC-COMPOUNDS AS MATURITY INDICATORS IN SOURCE ROCKS AND CRUDE OILS

Generally, these indicators rely either on an increase with maturity in the degree of alkylation of a given parent compound or a shift in the isomer distribution of alkyl-aromatic homologues towards thermally more stable isomers. A combination of both concepts in the Methylphenanthrene Index (MPI) resulted in an excellent maturity parameter, as demonstrated for rock extracts by an improved correlation with mean vitrinite reflectance (R//m) between 0. 65 and 1. 4%, i. e. , in the zone of oil formation. Organic facies effects should be taken into account in the interpretation of aromatic distributions of such source rocks and related crude oils. Aromatic maturity parameters are particularly useful in the maturity evaluation of post-mature crude oils and condensates. In contrast to biological markers, substantially higher concentrations of the key alkyl-aromatics persist at elevated maturation levels. Additional aspects of the subject are discussed.