Comparison of kinetic analysis of source rocks and kerogen concentrates

Shales and kerogen concentrates from the Green River, Rundel, Ohio, Draupne, and Phosphoria formations were examined by Pyromat II micropyrolysis and kinetic parameters were determined by the shift-in-Tmax, discrete distribution, modified Friedman, and modified Coats-Redfern methods. Overall, the shales and corresponding kerogens exhibited very similar kinetic parameters. Green River, Rundel, and Ohio shales and kerogens exhibited principal discrete activation energies of 54–57 kcal/mol, narrow distributions, and Tmax at 25°C/min heating rate around 480°C. Draupne and Phosphoria shales and kerogens exhibited kinetic parameters typical of Type II source rocks—principal discrete activation energies of 54–57 kcal/mol, broad distributions, and Tmax at 25°C/min around 459°C. The discrete distribution kinetic parameters were used to calculate oil generation at laboratory and geological heating rates. Each shale and corresponding kerogen exhibited generation curves and 50% generation temperatures that were very similar. The principal difference was that the kerogens exhibited slightly more oil generation at low temperatures compared to the corresponding shales. Some kerogens exhibited curves which were also shifted to slightly lower temperatures than those of the corresponding shales. For these specific shales and kerogens, the results indicate that kerogen isolation does little to affect the pyrolysis kinetic parameters. Although from a limited number of samples, these results suggest kerogen isolation may not be necessary to derive valid kinetic parameters.