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Kinetic models of vitrinite, kerogen, and bitumen reflectance

Author:
Burnham, Alan K.
Source:
Organic geochemistry 2019 v.131 pp. 50-59
ISSN:
0146-6380
Subject:
activation energy, bitumen, cross reaction, kinetics, models, organic matter, reflectance, rocks
Abstract:
Vitrinite reflectance is perhaps the most widely used property to calibrate paleothermal histories, and the most common model for that purpose is Easy%Ro. This paper reviews the origin of Easy%Ro as a simplification of Vitrimat. Weaknesses of the original versions are discussed, as are historical attempts to improve them. New versions of Vitrimat and Easy%Ro are presented that use substantially higher frequency factors and activation energies, and variations of these versions are derived for vitrinite itself and hydrogen-rich macerals and bitumen. The Vitrimat models are based on the original premise that reflectance correlates primarily with H/C ratio and secondarily with O/C ratio. With this approach, the reflectance of different types of organic matter is automatically calculated based on the initial composition of that organic matter. This general approach may also serve as a pathway with appropriate cross-reaction terms to calculate suppression of true vitrinite reflectance matured in oil-prone rocks containing significant concentrations of liptinite.
Agid:
6358374