The universality of the relationship between vitrinite reflectance and transformation ratio

When distributed kinetics became available several years ago some geochemists (including ourselves) started applying them without realizing that some of the assumptions, based on the use of single activation energy and frequency factor reactions, do not hold any more. One of these assumptions is that there is no universal relationship between vitrinite reflectance and transformation ratio across different heating histories or, in a broader sense, there is no universal relationship between calculated reaction rates if the reactions have different activation energies. Here we provide data and examples that show that when distributed kinetics are used, the relationship of vitrinite reflectance and transformation history is independent of heating history. However, because different kerogens have different kinetics, the relationship between vitrinite reflectance and transformation ratio needs to be established for each kerogen type. Once this relationship is established one can be used to calculate the other independent of heating history.