MATURITY TRENDS IN ASPHALTENES FROM PYROLYZED SOURCE ROCKS AND NATURAL COALS - MULTIVARIATE MODELING OF DIFFUSE-REFLECTANCE FOURIER-TRANSFORM INFRARED-SPECTRA

DRIFT spectra of asphaltenes have been modelled by multivariate method s to show the patterns of maturity dependent changes in chemical compo sition. The asphaltenes are from source rocks that have been artificia lly matured by hydrous pyrolysis, and cover a wide range of kerogen ty pes and maturity levels. Asphaltenes from a set of naturally matured c oal samples are modelled for comparison. The modelling results in defi ning a limited number of systematic trends in maturity dependent chemi cal changes in the spectra. The trends are comparable for similar sour ce rocks and are interpreted as representing defunctionalisation, arom atisation and cracking reactions. However, the timing and maturity dep endence of the reactions are specific for each source rock, and a gene ral maturation model that includes all source rock types could not be established.