HOW WELL CAN ARTIFICIAL COALIFICATION SIMULATE THE NATURAL MATURATION TREND

A modified Fischer retort apparatus was used to pyrolyze three organic-rich rocks (Types I, II and III) to various degrees of maturation. In order to test the feasibility of constructing hydrocarbon generation models from the pyrolysis data, we examined the coalification trends of natural and pyrolyzed coals. The maturation trend expressed by H/C vs O/C atomic ratio of the pyrolyzed coal-residues is very different from that of naturally matured samples. However, the trend expressed by H/C vs vitrinite reflectance of the pyrolyzed coal-residues and natural samples are very similar. In addition, the "H/C vs vitrinite reflectance" trend shown by the published data from both open-system pyrolysis (Rock-Eval) and from closed-system pyrolysis is very similar to that of the natural samples. Although the artificial coalification does not simulate the natural maturation perfectly, it seems to simulate the maturation trend expressed by "H/C vs vitrinite reflectance" rather well. Because the pyrolysis yield of the organic matter in organic-rich rocks (including coals) correlates closely with the H/C of kerogens, the artificial coalification should simulate the maturation trend expressed by "yield vs vitrinite reflectance" as well. This result justifies the simulation of petroleum yield of source rocks as a function of vitrinite reflectance using a pyrolysis apparatus such as the Fischer retort.