MODEL OF CATAGENESIS OF ORGANIC-MATTER

The chemical kinetic models are widely applicable to study of organic matter evolution in sedimentary rocks during catagenesis. Such models are used to reconstruct the dynamics and spatial position of main zone s of hydrocarbon generation in sedimentary basins. The commonest appro ach represents the process of hydrocarbon formation as a series of par allel independent reactions. More traditionally these questions were c onsidered in detail using analysis of evolution of chemical compositio n of organic matter. The scales of catagenesis, reflecting the spatial changes of intensity of gaseous and liquid hydrocarbon generation are developed in detail. Of interest is comparison of these approaches by the example of well-known Mesozoic deposits in West Siberia, for whic h one of the most substantiated scales of catagenesis zonation is deve loped. Four samples from the Urnenskaya and Kamennaya areas were studi ed to determine kinetic parameters. Previously the samples were extrac ted with chloroform and then were pyrolyzed at linearly increasing tem perature at an average rate of 24.45 K/s. The one-stage model with ind ependent reactions of first order was used to calculate kinetic parame ters and to simulate catagenesis zonation. It was assumed that the fre quency factor is constant for all reactions and the initial weight of the components by activation energy is distributed according to the Ga uss law. The calculations of spatial positions of the main zone of hyd rocarbon generation were made using three values of temperature gradie nt of 30, 40 and 50 K/km. The range of intensive generation is 1.5 to 4.5 km, which corresponds to the place of main zone of gas and oil for mation for the Mesozoic deposits of West Siberia and does not include deep zone of gas generation. Probably it results from multiple stages of the real process of hydrocarbon generation and the formation of int ermediate, thermally more stable components, leading expansion of a re al range of intensive generation.