To gain insight into geochemical reactions of petroleum relevance, we conducted hydrous pyrolysis reactions at 250, 300, 325, 350, 375 °C using sediments containing terrestrial, marine, and lacustrine kerogens as well as two modern biomass feedstocks. Immature kerogens, as well as generated residual kerogen, bitumen, and oil products were analyzed by solid-state <sup>13</sup>C NMR spectroscopy. From these data, carbon mass balances were developed to track organic matter structural changes across the oil window. A strong linear correlation (r<sup>2</sup> = 0.96) of the total mass of alkyl C in kerogen and bitumen with the maximum oil generation suggests that oil generation is largely dependent on aliphatic structures in kerogen.  Major structural transformations of organic matter were: the preferential hydrolysis of kerogen heteroatom structures below 250 °C, nonselective conversion of alkyl C and heteroatom C to oil and gas, respectively, at temperatures between 250 °C and 350 °C, and aromatization reactions and pyrobitumen formation at temperatures exceeding 350 °C. We tracked total oil, gas, and kerorgen C balances and the temperature-dependent sterane epimer ratios as independent measures of catagenesis reaction extent. The extent of catagenesis reactions at a given reaction temperature (energy) were variable with sulfur concentration and organo-mineral association.

Insights to catagenesis reactions from molecular mass balance in hydrous pyrolysis

2019 Spring National Meeting

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