APPLICATION OF A DETAILED CHEMICAL KINETIC-MODEL TO KEROGEN MATURATION

The determination of the oil generation kinetics from a given kerogen sample currently involves the assumption that high-temperature short-time laboratory data are equivalent kinetically to the geological conditions of low temperature and long times that existed as oil was generated. This extrapolation from around 400-degrees-C down to roughly 100-degrees-C covers a range in rate of about 14 orders of magnitude. Clearly, one must be fairly confident that the general chemistry that applies at the laboratory conditions also applies at geological conditions. We have modeled the conversion (pyrolysis) of carbonaceous material, such as kerogen, to liquids using a chemical mechanism consisting of elementary kinetic steps. The complexity of the material is handled by treating the material as a stochastic ensemble of molecules, each one consisting of a collection of different chemical functionalities. Taken together, the ensemble reflects the properties of the material and allows a kinetic description of the pyrolysis process. Hence, we can follow the properties of the hydrocarbons as they are produced. Because the model is rooted in fundamental chemistry (i.e., elementary reactions), it is believed that the extrapolation of the model rate constants to geological maturation conditions is valid. The results are consistent with the extrapolation of high-temperature laboratory kinetic data. These results support the contention that laboratory kinetic data can indeed be used to predict the timing/kinetics of the kerogen maturation process.