Naturally occurring complex processes of oil and gas generations in the source rocks can be simply approximated by several conceptual reactions; the primary cracking (oil and gas generation from kerogen), the secondary cracking (gas generation from oil), the formation of coke, and so on. The open-system pyrolysis and the selective hydrocarbon trap techniques are widely applied for the rapid method to calibrate kinetic parameters such as activation energy distribution, pre-exponential factor, and the composition of hydrocarbons from the primary cracking. Although kinetic parameters for the secondary cracking and the coke formation have not been fully tested yet, oil generation modelling is now practically useful for petroleum exploration. Modelling gas generation-expulsion in the deeper part of the basin is a major challenge to be overcome for the further development of basin modelling. For that context, we need more knowledge on reaction kinetics of thermal cracking of oils in the natural system. More plausible oil expulsion model is also required, since non-expelled oil can be one of the sources of thermogenic gas in the deeper part of the basin.
The reconstruction of thermal history of the effective source rock is critically important for modelling the oil generation history. Reasonable thermal history can be reconstructed based on computerized geohistory diagram with multi-thermal indicators; fluid inclusion homogenization temperature, kinetics of fission track disappearance, authigenic mineral transformations, vitrinite reflectance, and biomarker thermal indicators. Kinetic models of vitrinite reflectance, which are applicable to non-linear thermal history, have been newly proposed and applied to the calibration of thermal history. If we have more accurate and quantitative models on heat flow history and organic matter distribution with basin evolution, the generation modelling can be more useful for petroleum exploration.
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