Structural evolution in the kerogen during artificial and natural maturation by solid-state 13C NMR spectroscopy

For the first time we present the comparative analysis of the transformation of organic matter (OM) under conditions of artificial maturation and natural catagenesis by solid-state 13C NMR. The object of study was Domanik sediments of the Timan-Pechora basin containing OM at various stages of catagenesis (generally from MK1 to AK3). Experiments on OM catagenesis modeling under laboratory conditions (hydrous pyrolysis of chloroform-extracted rocks in autoclaves at 300, 325 и 350 °С) resulted in OM artificial maturing. 13C NMR 2D HETCOR spectra, obtained for kerogen from Domanik sedimentary rocks heated at different temperatures in autoclaves, and kerogen extracted from Domanik rocks from a number of boreholes and natural sections of the Timan-Pechora basin, indicate similar changes in its structure expressed in the transition of alkyl-substituted carbon (in aromatic ring) into intercyclic carbon. During artificial OM maturing this process proceeds more rapidly than natural catagenesis.