Kinetic analysis of California petroleum source rocks by programmed temperature micropyrolysis

Three California shales were examined by micropyrolysis to determine laboratory pyrolysis kinetics. Samples from the Modelo Formation with 6.16 wt % S in kerogen, Monterey Formation with 13.58 wt % S in kerogen, and with 8.88 wt % S and 13.16 wt % O in kerogen, exhibited shift-in-Tmax and principal discrete distribution energies of 54 and 57, 51 and 52, and 65 and 59 kcal/mol, respectively. These results are evidence that laboratory decomposition kinetics of high sulfur kerogens and, in particular, Monterey kerogens appear not to be governed by organic sulfur content alone, particularly because the kinetic parameters for the 13.16 wt % O Monterey sample were well outside the range generally seen for type I, II, and II-S kerogens, and closer to Type III kerogens.