Abstract
Computer-aided maturity modeling and reconstruction of thermal history of the rock have become important and routine parts of sedimentary basin analysis and petroleum exploration. In performing simulations of organic maturation, it is extremely important to have a more reliable information about the thermal history of the rock. Various kinetic and non-kinetic thermal indicators have been proposed and applied to the reconstruction of thermal history. Among several organic thermal indicators, sterane isomer ratio and vitrinite reflectance are the most typical molecular and macromolecular thermal indicators, respectively. Many studies on their kinetic modeling have been performed in the 1980s to the early 1990s.
Sterane epimerization, which had once impressed us as an ideally simple uni-molecular reaction useful for paleo-temperature analysis, is now considered not to occur in nature. Various complex reactions concern the evolution of sterane isomer ratio in the sedimentary basin. However, this does not deny the value of sterane isomer ratio as a useful thermal indicator, since complex reaction process can often be simply expressed by the first order reaction kinetics. The same is true in modeling evolution of macromolecular organic matter. Maturation of kerogen or vitrinite can be modeled simply by the pseudo-first order kinetic reactions.
Geochemical model for organic maturation represents gross simplifications of what must be an enormously complex natural system. Numerical model does not express real geochemical process in nature, but expresses geochemical concept of organic maturation. Model construction itself can enhance insight into organic geochemistry. Our increasing knowledge on organic geochemistry can be linked with knowledge of other geological sciences by geochemical modeling. Geochemical modeling can expand the potential of organic geochemistry.
